Philips Tech. Rev. 42, No. 2, 59-64, Aug. 1985 59

On the mechanism of the corrosion of glass by water

B. M. J. Smets

Modern methods of surface analysis such as SJMS and ESCA can help us to obtain a betterunderstanding of the basic processes in the leaching of glass. These studies are of interestbecause of new applications of glass, such as the DOR disc and glass fibres for optical com-munication.

Glass, its structure and its resistance to chemicalattack

Window glass or soda-lime glass contains about100/0 of sodium, 7% of calcium, 1% of aluminium,and perhaps small quantities of potassium and mag-nesium as well as silicon and oxygen, of course. In thecontext of the investigation described in this article wecan consider the structure of glass to be represented,as in Zachariasen's theory, by a random three-dimen-sional network of oxygen tetrahedra, with the centresoccupied by the Si4+ ions and the A13+ ions, while theNa+ and the Ca2+ ions occupy the interstices of thenetwork (fig. Ja) [1]. The oxygen atoms can fulfil twofunctions in the network: they can be bridging oxygenatoms, each forming a covalent bond with two siliconatoms, or non-bridging oxygen atoms, each forming acovalent bond with one silicon atom and an ionic bondwith one sodium ion (or with half a calcium ion). AtPhilips Research Laboratories a study has been madeof alkali- and alkali-calcium silicate glasses, as simplervariants of window glass, with the compositions20Na20.80Si02, 20Na20.10CaO.70Si02 etc. (molarratios), and of aluminosilicate glasses with the corn-position 20Na20.xAI203.(80 - x)Si02. A typicalstructural characteristic of aluminosilicate glasses,compared with the glasses mentioned earlier, is the de-creasing content of non-bridging oxygen atoms withincreasing content of A1203; the alkali ions are thenlinked by AI04 - tetrahedra (fig. 1b).

Glass windows have to be able to withstand atmos-pheric effects for many years without showing visible

Dr B. M. J. Smets, now with the Philips Lighting Division, wasformerly with Philips Research Laboratories in Eindhoven. In 1983he received the w. A. Weyl International Glass Science A ward forthe work described briefly here.

Ned. Philip s Bedrijven B.V.PHILIPS RESEAnCH LABS

l.iEl!~Ai::;;Y W'{ - 1P 0 Box 80.000

5600 ,JA EIN[JHOVENTHE NETHERLANDS

changes. Similarly, household glassware must be resis-tant to substances such as hot water, fruit juices, diluteacids and alkalis. Laboratory glassware must be resis-tant to highly concentrated reagents at high tempera-tures. Special requirements are also necessary for glassused in incandescent lamps, glass insulators, signallamps and in the various applications of optical glass,to mention only a few examples.

In many cases the way in which glass reacts to water,may be regarded as a key property, which could be

Q

Fig. La) Schematic two-dimensional structure of alkali-calciumsilicate glasses, from Zachariasen's theory [11. 0 bridging oxygenatom. • non-bridging oxygen atom .• network-forming ion, inthis case an Si4+ ion .• network-modifying ion, in this case analkali ion. b) The structure of aluminosilicate glasses, in which A13+ions ( .) occur as network-formers. With increasing content of A13+ions the number of non-bridging oxygen atoms decreases (to zerohere) and the network-modifying ions are attached to AI04 - tetra-hedra. Aluminosilicate glasses therefore have a much less openstructure.

[11 See for example J. M. Stevels, Philips Tech. Rev. 22, 300-311,1960/61.

60 B. M. J. SMETS PhiJips Tech. Rev. 42, No. 2

studied for clues to the ability of glass to resist otherchemicals.It has long been known that pure water 'leaches'

glass. When the glass comes into contact with water,the alkali ions, which are fairly loosely attached to thenetwork, are especially likely to diffuse in small quan-tities to the surface and disperse, giving rise to analkali depletion layer, of a few microns at most, at thesurface. In this process OH- ions are released, whichcan then take part in a reaction in which covalentSi-O-Si bonds are broken and part of the glass net-work is dissolved - although extremely slowly.Significant corrosion rates of a few millimetres a

year are only found if the glass is continuously in con-tact with water and only if the water is not drainedaway. In most conventional applications of glass thisleaching effect, is therefore no problem. But it is aproblem in some of the recent applications of glass,like optical fibres 'and DOR discs.

Glass fibres for optical communication are coveredwith a thin protective coating of a synthetic mat-erial [21. This material, like all plastics, always allowssome water to pass through it and the thin film ofwater that can then form between the glass and thecoating may become fairly strongly alkaline, as aresult of leaching. The dissolution of the glass net-work that then starts may cause crazing, ultimatelyleading to fracture if the glass comes under pressure.(This does not of course apply to optical fibres madeof quartz glass, which contains no alkali ions.)The leaching of glass is also an effect that must be

studied if DOR discs of high quality are to be pro-duced (DOR is a digital optical recording system devel-oped by Philips (31). In the DOR disc the informationis contained in a recording layer consisting of a thinfilm of TeSeSbS applied, with an intermediate layer oflacquer, to a glass substrate. Alkali ions released byleaching due to the penetration of ambient moisturecould easily destroy the recorded information.Applications like this have made it desirable to

study such corrosion effects, which extend to only afew microns below the surface of glass. The develop-ment some time ago of surface-analysis methods suchas SIMS (Secondary-Ion Mass Spectrometry) andESCA (Electron Spectroscopy for Chemical Analysis)make this possible. In this article the results will begiven of an investigation carried out with suchmethods at Philips Research Laboratories into themechanism of the corrosion of glass by water: A gen-eral description of the methods of analysis that weused has been given in earlier articles in this journal [41,

and details of their application to the area of investi-gation described here have been described elsewherein the literature [51. '

The corrosion of alkali- and alkali-calcium silicateglasses by water: ion exchange?

Fig. 2 gives an example of the sodium profilefound on leaching at the surface. The profile wasmeasured with SIMS for glass of the composition20Na20.80Si02• It was found 'that the thickness ofthe.depletion layer, defined as the depth at which thesodium concentration has reached half the value inthe bulk of the glass, increases linearly with the square

1

1-z

3f.Lm

Fig. 2. Sodium profiles measured by SIMS (CNa is the local concen-tration divided by the bulk concentration and z is the depth beneaththe surface) of a glass with composition 20Na20.80Si02 that hasbeen exposed to pure water at 70 oe for 5 (lef!), 15 and 60 minutes.

Î

1.0

0.5

~ 0 " •• : • .: •• : ..o t ~.~. 0.1 ... x··o ...,.....o 2 3 4 5x10-Bms'/2

_ Z/(t'!2)

Fig. 3. Results of the same experiments as in fig. 2, represented byplotting the sodium concentration CN. against the depth z dividedby the square root of the time t. The theoretical curve, based on ionexchange, is also shown.

root of the time that the glass has been in contact withwater. A plot of the sodium concentration against thedepth divided by the square root of the contact time,as in fig. 3, shows a neat fit with the experimentalprofiles for different times.

The variation as the square root of the time is anindication that diffusion is the rate-determining pro-cess of leaching, resulting in the S-shaped concentra-tion profiles shown. An obvious assumption is that

Philips Tech. Rev. 42, No. 2 CORROSION OF GLASS BY WATER 61

diffusion in these glasses causes an exchange betweenhydronium ions (HaO+, the ionic form in which H+usually occurs in water) and sodium ions,in the re-action:

== SiO-Na+ + HaO+ -+- == SiO-HaO+ + Na". (1)

In this reaction the group == SiO- represents a siliconplus non-bridging oxygen group.The ratio of the diffusion coefficients DNa and DH

for sodium and hydronium ions then determines theexact shape of the concentration profiles, as calculatedin fig. 4 for a number of values of the diffusion coef-ficients. Bymatching these theoretical profiles to thosefound experimentally the diffusion coefficients can bederived; see Table J. It is always found that the valuederived for DNa, which in principle applies only at thesurface, is much larger than the value measured for

Fig. 4. The calculated variation of the sodium concentration eNaasa function of Zj(DHt)I/2, for various values of 10gDHjDNa. In allcases it has been assumed that the leaching was due to ion exchange.

the bulk diffusion of sodium. It is, of course, conceiv-able that the greater mobility of sodium at the surfacefound in this way is due to the difference in composi-tion between the surface depletion layer and the bulkof the glass.

However this may be, it must at the very least beaccepted from the results of other recent investiga-tions that the mechanism is more complex than haspreviously been assumed. To start with, it was estab-lished some years ago, by measurements of the diffu-sion of radioactive tracers, that the diffusion coeffi-cient for sodium in a depletion layer is certainly notgreater, as the above model suggests, but smaller than

in the bulk of the glass [61. It is also difficult with theexisting theory to explain why the concentration ofthe sodium ions in the leached layer does not becomezero, but 5 to 10070 of the initial concentration - as isalways found experimentally (fig. 3). Also because ofmeasurements by nuclear reaction analysis it has longbeen assumed that one sodium atom is exchanged forthree hydrogen atoms (reaction 1), in accordance withthe existing theories: but further experimental investi-gation has shown that the exchange ratio varies from1.7 to 3.2, depending on the type of glass [71. If wewish to explain these values by assuming that protons,and then H20 molecules, are exchanged and nothydronium ions, we would expect that the use of

Table J. The diffusion coefficients DH and DNa of hydronium andsodium ions for some types of glass, calculated from sodium pro-files on the assumption that the leaching takes place by ion ex-change. The calculated values of DNa, applicable only at the sur-face, are in that case much greater than the value DbNameasured inthe bulk of the glass.

Composition DH DNa DbNa(m2çl) (m2s-l) (m2çl)

2ONa20.80Si02 5.10-17 5.10-11 5.10-19

20Na20.10CaO.70Si02 4.10-19 4.10-16 5.10-20

IONa20.10K20.10CaO.70Si02 5.10-19 5.10-14 10-23

deuterium instead of protons in the water for leachingthe glass would result in a 20% smaller depletion layerowing to the larger mass of the deuterium. No suchisotopic effect could be demonstrated, however [81.

This can only mean that, if the diffusion of a compo-nent containing hydrogen is the rate-determining step,.this component must be a relatively heavy compoundsuch as HsO+ - after all- or perhaps H20. Experi-mental observations of this kind, which were so diffi-cult to explain, led us to consider another mechanismfor the leaching process.

[2] See for example H. M. J. M. van Ass, P. Geittner, R. G.Gossink, D. Küppers and P. J. W. Severin, Philips Tech. Rev.36, 182-189, 1976, in particular p. 185.

[3] See for example L. Vriens and B. A. J. Jacobs, Philips Tech.Rev. 41, 313-324, 1983j84.

[4] H. H. Brongersma, F. Meijer and H. W. Werner, Philips Tech.Rev. 34, 357-369, 1974.

[6] See for example R. G. Gossink, Glass Technol. 21, 125-133,1980;B. M. J. Smets and R. G. Gossink- Fresenius Z. Anal. Chern.314, 285-288, 1983;B. M. J. Smets, M. G. W. Tholen and T. P. A. Lommen, J.Non-Cryst, Solids 65, 319-332, 1984.

[6] M. Takata, J. Acocella, M. Tomozawa and E. B. Watson, J.Am. Ceram. Soc. 64, 719-724, 1981. .

[7] I. S:T. Tsong, C. A. Houser, W.,B. White, A. L. Wintenberg,P. n.Miller and C. D. Moak, Appl. Phys. Lett. 39, 669-670,1981.

[8] See for example B. M. J. Smets and T. P. A. Lommen, J.Physique 43 (Colloque C9), C9j649-C9j652, 1982. .

62 B. M. J. SMETS Philips Tech. Rev. 42, No. 2

The corrosion of alkali- and alkali-calcium silicateglasses by water: dlffusion of H20?

If glass leaches more rapidly than might be expectedfrom the measured "valueof the mobility of the alkaliions, it seems likely that a neutral molecule will be therate-determining diffusing component. The move-ments of such a neutral component will encounterlittle resistance from the presence of negatively chargednon-bridging oxygen atoms in the glass structure. Theabsence of an isotopic effect also led us to concludethat the diffusing entity must be a relatively heavymolecule. The H20 molecule satisfies both conditions,and it is present in excess.

What happens to the glass network when water dif-fuses into it? We can answer this question to some ex-tent with the aid of electron spectroscopy (ESCA).Fig. 5a shows part of the ESCA spectrum of a soda-lime glass. 'Three energy transitions can be identified:one transition at a relatively low kinetic energy, due tosodium, and two transitions attributable to oxygenatoms - and with different charge densities. The dif-ference of about 2.5. eV between the energy of thesetwo transitions corresponds to the difference in chargedensity between the negatively charged non-bridgingoxygen atoms and the non-charged bridging oxygenatoms.If the sample analysed is immersed in water and

then analysed again, the spectrum shown in fig. 5b isobtained. The peak attributable to sodium has almostdisappeared, as also has the peak due to the non-bridging oxygen atoms. The disappearance of thesodium ions is seen to be accompanied by the dis-appearance of the negative groups to which they wereattached. The most obvious explanation for this isthat, under the influence of thè inward-diffusing water,non-bridging oxygen atoms are converted into silanolgroups (== SiOH), in which the oxygen atom has vir-tually the same charge density as the bridging oxygenatom:

== SiO-Na+ + H20:±+ == SiOH + Na+OH-. (2)

This reaction enables the -sodium ions - no longerattached to the glass network - to diffuse to the sur-face, with OH- ions as co-ions,If the diffusion of water is the rate-determining step

in this process, it follows anyway that S-shaped sodiumprofiles ought to be obtained (fig. 6). The forward tiltof the S of the profile then depends on the equilibriumconstant K of reaction (2) and on the local concentra-tion of H'20 at the glass surface.

But this hypothesis contains even more that fits inwith the facts. It was 'mentioned earlier that it wasoriginally thought that Na and H atoms were ex-changed in the ratio 3: 1 for all types of glass. For the

concentrations of Na and H atoms found in the deple-tion layer this should give a ratio of (i - a)/3a, where iis the initial concentration of Na atoms and a is theproportion of them exchanged. However, now it hasbeen established that the exchange ratio varies from1.7 to 3.2, depending on the type of glass used, thismust of 'course mean that the concentration ratio ofNa and H, atoms found in the depletion layer musthave a spread of (i - a)/ 1.7a to (i - a)/3 .2a.

1

t

BD

-7.5Q -£-£0

I

t

-7.5Q

o 2.5-£-£0

5.0eV

Fig. S. ESCA spectra of a) a sample of the composition20Na20.10CaO.70Si02, and b) the same part of the sample after10minutes in water at 20°C, The peak Na corresponds to a sodium-Auger transition, the peak BO is due to bridging oxygen atoms andthe peak NBO to non-bridging oxygen atoms.

0.1

t

Fig. 6. Calculated curve of the sodium concentration CNa as a func-tion of Z/(DH,ot)1/2, for different values of the equilibrium con-stant K of reaction (2). It has been assumed that the leaching wasdue to diffusion of H20.

Philips Tech. Rev. 42, No. 2 CORROSION OF GLASS BY WATER 63

CH20 05

CH 1.000.750.500.250.05

This scatter in values can be more easily explainedwith the diffusion of H20 as the rate-determining steprather than ion exchange, since the number of Hatoms in the depletion layer will then be determinedby the number of silanol groups formed in the glassand also by the concentration of H20 in the glass.Depending on the equilibrium constant K, the concen-tration of H20 in different types of glass, with thenumber of silanol groups remaining unchanged, maydiffer, and the ratio of Na and H atoms could have acorresponding spread of values (figs 7 and 8).

The theoretically calculated and experimentally de-termined Na and H profiles shown in these figures arenot complementary - and they do not need to be forthe model we are now considering. But they wouldhave to be complementary if they were due to ion ex-change.

Another point in agreement with the experimentaldata of fig. 8 is that in our hypothesis some of the Naions will always remain behind in the leached layer:the equilibrium of reaction (2) is never completelyshifted to one side.

05 05 r

o

Fig. 7. H and Na profiles (red) calculated from the H20 diffusionmodel for different values of the water concentration CH,O (localconcentration at the surface divided by the bulk Na concentration).The equilibrium constant K of reaction (2) is taken such that theresidual concentration of sodium is 5070of the sodium concentra-tion in the bulk of the glass (this is usually so in practice). In the newmodel the hydrogen concentration can assume smaller values thanthree times the concentration of outward-diffusing sodium ions;this would be impossible with the model discussed earlier of ion ex-change between hydronium and sodium ions.

A final remark about this part of the investigation:the experimentally determined profiles can always be'translated back' into an equilibrium constant of re-action (2) and a diffusion coefficient for H20, applic-able at the surface. Since they relate only to a verythin layer at the surface, both quantities are difficultto measure experimentally, if at all; nor has it yetproved possible to bring them into relationship withother experimental data, and they cannot therefore be

25.--------.-----------

1.0

\

20

\

\\

\

1.5

\\\\\\

10

05 r

42

Fig. 8. H and Na profiles (squares and crosses respectively) deter-mined experimentally by SIMS in 20Na20.10CaO.70Si02 aftertreatment with water at 70 DC. The continuous curves (black for Hand red for Na) were calculated with the values 0.75 for CH,O,

3.9 X 10-2 for K and 7.3 X 10-18 for DH,O' The profiles are clearlynot complementary, as they should be for the ion-exchange model(the dot-dash line gives the calculated complementary H profile).

checked against reality. On the basis of the data usedso far it is therefore not yet possible to make a defi-nitive statement about the validity of the proposedmechanism.

However, the usefulness of this model also becameapparent when we extended the investigation to alu-minosilicate glasses.

The corrosion of aluminosilicate glasses by water: ionexchange or diffusion of H20?

The mechanism that we have proposed, with thediffusion of H20 as the rate-determining step, de-pends essentiallyon the presence of non-bridging

64 CORROSION OF GLASS BY WATER Philips Tech. Rev. 42, No. 2

x=20 ID 5

200 400 600nm--z

Fig. 9. Na profiles of aluminosilicate glasses of the composition20Na20.xAI20a.(80-x)Si02, determined experimentally with SIMS,for different values of x and after being in contact with water at70 °C for 16 hours.

oxygen atoms in the glass. Aluminosilicate glasseswith an Al content higher than the Na content containno non-bridging oxygen atoms and all the sodium ionsare bonded to Al04- groups. In these glasses, there-fore, reaction (2) is impossible and in this case thesodium ion would only be removed by an ion ex-change process, which is slower.

From jig. 9 it does indeed appear that the pre-sence of Ab03 in glasses of the composition20Na20.xAb03-(80-x)Si02 has a pronounced effecton the action of water on the glass. The larger thevalue of x, the slower the leaching. It is also note-worthy that glasses with x = 5 and 10 have a distinctplateau in the sodium profile. We know for examplethat in the glass with 5 mol07o of Al203 one quarter ofthe sodium ions will be attached to Al04 - groups, andthree quarters to non-bridging oxygen atoms. It isclear from the measured profile that in this glass threequarters of the ions diffuse rapidly while the other

quarter diffuses much more slowly to the surface. Forthe glass with 10 mol07o of Ah03 half of the sodiumions are attached to A104 - groups and the other halfto non-bridging oxygen atoms. We see here that theplateau does indeed occur at 50070of the initial Na con-centration. It has been demonstrated that glasses with20 mol07o of Ab03 contain no non-bridging oxygenatoms, and here the whole leaching process does infact take place very slowly. For the sodium ions thusexchanged we find a diffusion coefficient DNa equal to2 X 10-19 m2ç1, corresponding in order of magnitudeto the diffusion coefficient of sodium ions in the bulkof the glass (Table I). All this is in complete accordwith the expected behaviour, as described in the fore-going.

On the basis of the mechanism we have found forthe corrosion of glass by pure water we also per-formed experiments in which the pH of the water wasvaried. The measured corrosion behaviour could alsobe satisfactorily explained in terms of our model.

Summary. The use of modern methods of surface analysis has ledto a new hypothesis for the mechanism of the leaching of alkali-calcium silicate glasses. The distribution of the sodium ions at thesurface upon leaching, determined by SIMS, and the associatedchanges in the content of non-bridging oxygen atoms, measured byESCA, as well as the resulting ratio of H and Na atoms in the deple-tion layer, can now be more satisfactorily explained if it is assumedthat the rate-determining step is not ion exchange but the diffusionof H20. These H20 molecules enter into a reaction with non-bridg-ing oxygen atoms in the glass, forming silanol groups and releasingOH- ions. As a result of this reaction the neighbouring Na ions areno longer attached to the glass network and can easily diffuse to thesurface, together with OH ions as co-ions. In aluminosilicate glassesthe Na ions attached to AI04 - tetrahedra cannot be released bysuch a reaction. This then takes place by ion exchange, and muchmore slowly.

Philips Tech. Rev. 42, No. 2, 65-68, Aug. 1985

Scientific publicationsThese publications are contributed by staff of laboratories and plants that form part of orcooperate with enterprises of the Philips group of companies, particularly by staff of the re-search laboratories mentioned below. The publications are listed alphabetically by journal title.

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Measurement of the refractive index and optical ab-sorption spectra of epitaxial bismuth substitutedyttrium iron garnet films at uv to near-ir wavelengths

P. Chambon, M. Erman, J. B. Thee-ten, B. Prévot* & C. Schwab* (* Univ.Louis Pasteur, Strasbourg) L

Spectroscopie ellipsometry and Raman scatteringstudy of the annealing behavior of Be-implantedGaAs

P. Delsarte, Y. Genin & Y. Kamp B Parametrie Toeplitz systems

D. Meyer-Ebrecht & T. WendIer H An architectural route through PACS

Appl. Phys. A 34 223-230 1984

Appl. Phys. Lett. 45 390-392 1984

Circuits Syst. & 207-224 1984Signal Process. 3

Computer 16 (No. 8) 19-28

W. G. Essers & G. A. M. Willems E Plasma-MIG-SchweiBen - SchweiBen von Alumi- DVS-Berichte 90nium, Auftragschweiûen und Zweielektroden-schweiBenvon Baustahl

J. H. Waszink & M. J. Piena

9-14

E Erzeugung und Transport von Wärme beim DVS-Berichte 90SchweiBenmit Stabelektroden

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A. E. Ronner (Philips ISA-CQM, Generalization of M(x)-matricesEindhoven) & E. Sterken (Univ.Groningen)

F. Hottier & M. Fink L Characterisation of biological tissue by ultrasound

B. Hill & K. P. Schmidt H Optischer Bildmustergenerator in Festkörpertechnikfür elektrophotograflsche Drucker

H. V. Ulmer", K. Würthner* (* Univ.-Frauenklinik, Hamburg) & K. M.Lüdeke H

Vergleich von Mikrowellen- und Infrarotthermo-graphie bei der Entdeckung von malignen Brust-tumoren

G. Kersuzan (TRT, Le Plessis-Robin-son) & A. G. van Nie E

Modèles de calcul précis pour la détermination deI'augmentation de température de sources de chaleurrectangulaires dans les circuits hybrides

F. L. H. M. Stumpers E The history, development, and future of telecom-munications in Europe

K. S. Chung E Generalized tamed frequency modulation and its ap-plication for mobile radio communications

H. J. M. Veendrick E Short-circuit dissipation of static CMOS circuitryand its impact on the design of buffer circuits

A. Thayse B A matrix formalism for asynchronous implementa-tion of algorithms

P. Piret B Multiple-word correcting convolutional codes

Econ. Lett. 16 321-326 1984

Europhysics News 15 12-16 1984(No.8/9)

Feinwerktech. & 189-192 1984Messtech.92

Fortschr. Röntgenstr. 208-211 1984141

Hybrid Circuits No. 5 4-11 1984

IEEE Commun. Mag. 84-95 198422 (No. 5)

IEEE J. SAC-2 487-497 1984

IEEE 1. SC-19 468-473 1984

IEEE Trans. C-33 289-300 1984

IEEE Trans. IT-30 637.c644 1984

65

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1984

1984

66 SCIENTIFIC PUBLICATIONS

P. Röschmann H Intrinsic relaxation of the ferromagnetic resonance IEEE Trans. MAG-20 1213-1215 1984in substituted yttrium iron garnets

993-1007 1984

Philips Tech. Rev. 42, No. 2

P. Blood & J. J. Harris R Deep states in GaAs grown by molecular beam epi- J. Appl. Phys. 56taxy

Influence of clustering on the mobility of Ill-V semi-conductor alloys

67Fe Mössbauer effect in ThFe6 hydride

Growth of multiple thin layer structures in theGaAs-AIAs system using a novel VPE reactor

Growth of (AI,Ga)As/GaAs heterostructures forHEMT devices

Characterization of metallic precipitates in epi taxi alSi by means of preferential etching and TEM

Manufacture of LaserVision discs by a photopoly-merization video process

Photopolymerizable coatings for LaserVision videodiscs

De toepassing van AI20a als keramisch lampomhul-lingsmateriaal

Structural properties of dielectric layers followingC02 laser irradiation of SOl structures

.Visually controlled robots for unpacking andmounting television deflection units

Three-weight codes and association schemes

J. Appl. Phys. 56

J. Appl. Phys. 56

J. Cryst, Growth 68

J. Cryst. Growth 68

P. J. Roksnoer E The mechanism of formation of microdefects in sili- J. Cryst. Growth 68con

J. Electrochem. Soc. 1388-1391 1984131

K. de Kort E Interactions and localisation effects in sputtered Ru J. Phys. C 17and Ru02 films

J. Radiat. Curing 11(No. 1)

J. Radial. Curing 11(No. I)

L. D. Knox N Squeeze film forces in a magnetic shaft suspension J. Tribol. 106system

Klei/Glas/Keramiek 5 210-215 1984

H Site selectivity in praseodymium- and bismuth-sub- Mater. Res. Bull. 19stituted gadolinium gallium garnet epilayers

H Dissolution of iron garnet LPE layers in acidic solu- Mater. Res. Bull. 19tions containing reducing agents

. Mater. Res. Soc.Symp. Proc. 33

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B A method of code generation for algorithmic lan- Philips J. Res. 39guages

B Block decomposition and iteration in stochastic Philips J. Res. 39matrices

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E Influence of short-range order on the thermal stabil- J. Non-Cryst, Solids 43-51 1984ity in amorphous Hf-Ni alloys 68

E Raman study of the water adsorption on monolithic J. Non-Cryst, Solids 163-166 1984silica gels 68

5237-5260 1984

2-9 1984

E Time-frequency distributions of loudspeakers: the J. Audio Eng. Soc. 31 198-223 1983application of the Wigner distribution

E Digital distortion analyzer J. Audio Eng. Soc. 32 539-541 1984

E An optimum time step length for convergence to J. Cornput. Phys. 56 356-360 1984steady-state solution in cornpressiblé-flow calcula-tions

P. Blood & A. D. C. Grassie (Univ.Sussex, Brighton) R

P. C. M. Gubbens*, A. M. van derKraan" (* Interuniv. Reactor Inst.,Delft) & K. H. J. Buschow E

C. P. Janse & A. J. M. Kaizer

E. Stikvoort

A. M. J. G. van Run

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C. J. Werkhoven, C. W. T. Bulle-Lieuwma, B. J. H. Leunissen &M. P. A. Viegers S, E

K. H. J. Buschow

D. M. Krol & J. G. van Lierop

A.-J. M. van den Broek, H. C. Haver-kom van Rijsewijk, P. E. J. Legierse,G. J. M. Lippits & G. E. Thomas E

J. G. Kloosterboer & G. J. M. Lip-pits E

P. R. Prud'homme van Reine (PhilipsLighting Div., Eindhoven) & G. deWith E

C.-P. Klages

C.-P. Klages

H. Baumgart, E. Arnold, J. Petru-zello, T. F. McGee&M. H. Frommer

N

P. Saraga, C. V. Newcomb, P. R.Lloyd, D. R. Humphreys & D. J.Burnett R

A.. R. Calderbank (AT&T Bell Labs,Murray Hili, NJ) & J .-M. Goethals B

P. Branquart

P. J. Courtois & P. Semal

10-21 1984

473-476 1984

633-642 1984

1329-1336 1984

87-92 1984

512-517 1984

143-152 1984

153-177 1984

178-194 1984

P. Delsarte, Y. Genin & Y. Kamp B Application of the index theory of pseudo-lossless Philips J. Res. 39functions to the Bistritz stability test

Philips Tech. Rev. 42, No. 2 SCIENTIFIC PUBLICATIONS

C. Couvreur & P. Piret B Codes between BCH and RS codes

M. Davio B Algorithmic aspects of digital system design

C. Dierieck & F. Crowet B Helmholtz decomposition on multiply connecteddomains

B. M. J. Smets & D. M. Krol E Group III ions in sodium silicate glass. Part 1. X-rayphotoelectron spectroscopy study

E Group III ions in sodium silicate glass. Part 2.Raman study

D. M. Krol & B. M. J. Smets

M. Davio & J.-J. Quisquater B Contemporary evolution in cryptographic techniques

P. Röschmann H Ringresonator RF-pro bes for proton imaging above1 Tesla

P. I. Kuindersma, A. Valster & W.Baks E

1.3 urn buried heterojunction laser diodes under highelectrical stress: leakage currents and aging behavior

P. I. Kuindersma & A. H. E. Wille-kes E

On the CW multimode behavior of 1.3 urn buriedheterojunction laser diodes

G. D. Khoe, L. J. Meuleman & J.Poulissen E

Laser diode devices for coherent fibre optics andspecial applications

The first GaAs fully integrated microwave receiverfor DBS applications at 12 GHz

C. Kermarrec, J. Faguet, B. Vancon,C. Mayousse, A. Collet, P. Kaikati& D. Beaufort L

R. Meierer & C. Tsironis L Optimum design of dual gate MESFET amplitudemodulators

V. Pauker, B. Bru & M. Binet L High real estate efficiency, wideband monolithicGaAs amplifiers

A. Mitonneau, M. Rocchi, I.Talmud,J. C. Mauduit & M. Henry (CNET,Lannion) L

Direct experimental comparison of submicron GaAsand Si NMOS MSI digital ICs

H. Sari L Baseband equalizer performance in the presence ofselective fading

H. Bourlard, C. J. Wellekens & H.Ney B,H

Connected digit recognition using vector quantiza-tion

H. K. Kuiken E Etching through a slit

D. Guyornar, M. Fink & R. H. Cour-sant L

Acoustical displacement reconstruction ofaxisym-metric transducers

M. Naillon, F. Besnier (CISI, Paris)& R. H. Coursant L

Finite element analysis of narrow piezoelectric paral-lellepiped vibrations; energetical coupling modeling

J. L. Bernatets & F. Hottier L Estimation of frequency dependent attentuation inbiological tissue by a time-frequency representationof the echographic A-lines

J. F. Cardoso & M. Fink (Univ. LouisPasteur, Strasbourg) L

B. Strocka, P. Hansen & H. Heit-mann H

Diffraction correction in pulse-echo attenuationmeasurements

The annealing behavior of ion-irradiated garnetcrystals

P. C. Zalm E A critique ~f semiempirical formulae for the sputter-ing yield near threshold energy

N Sputter-sealed IR windows resist thermal effectsR. L. Bronnes & R. C. Sweet

G. F. Neumark & K. Kosai, (Santa Deep levels in wide blind-gap IlI-V semiconductorsBarbara Res. Center, Goleta, CA) N

67

Philips J. Res. 39

Philips J. Res. 32

195-205 1984

206-225 1984

226-241 1984

Philips J. Res. 39 242-253 1984

Phys.&Chem. 113-118 1984Glasses 25

Phys. & Chem. 119-125 1984Glasses 25

Phys. Technol. 15 191-196 1984

Proc. 3rd Ann. Meet- 634-635 1984ing Soc. Mag. Reso-nanceMed., NewYork1984

Proc. 10th ECOC, 64-65 1984Stuttgart 1984

Proc. 10th ECOC, 66-67 1984Stuttgart 1984

Proc. 10th ECOC, 134-135 1984Stuttgart 1984

Proc. 14thEur.Micro- 749-7541984wave Conf., Liège 1984

Proc. 14th Eur. Micro- 767-772 1984wave Conf., Liège 1984

Proc. 14th Eur. Micro- 773-776 1984wave Conf., Liège 1984

Proc. GaAs IC Symp.,Boston 1984

3-6 1984

Proc. GLOBECOM'83, San Diego 1983

Proc. ICASSP 84,San Diego 1984

7 pp. 1983

4 pp. 1984

Proc. R. Soc. LondonA 396

95-117 1984

Proc. Ultrasonics 766-769 1983Syrnp., Atlanta 1983

Proc. Ultrasonics 773-777 1983Symp., Atlanta 1983

Proc. Ultrasonics 835-840 1983Symp., Atlanta 1983

Proc. UltrasonicsSymp.çAtlanta 1983

Radiat. Eff. 72

841-846 1983

219-227 1983

Radiat. Eff. Lett. &6 29-34 1984

Res. & Dev. . 130-q3 1984(November 1984)

Semiconductors andsemimetals, Vol. 19,R. K. Willardson &A. C. Beer (eds), Aca-demic Press, NewYork

1-74 1983

68 SCIENTIFIC PUBLICATIONS Philips Tech. Rev. 42, No. 2

C. Loty L A 7 GHz CRT for rea!time digital oscilloscopy SID 83 Digest, Phila- 126-127 1983delphia 1983

SID 84 Digest, San 262-263 1984Francisco 1984

SMPTE J. 93 726-729 1984

Technology of Nuclear 217-231 1984Magnetic Resonance,P. D. Esser & R. E.Johnston (eds), Soc.Nucl. Med., NewYork

C. Loty L Improved simulation of electron beams

J. S. Nadan & R. N. Jackson N, R Signa! processing for wide-screen television: thesmart receiver

S. G. Einstein (Philips Medical Sys-tems, Shelton, cn,A. A. Maudsley*,S. K. Mun*, H. E. Simon*, S. K.Hilal* (* Columbia PresbyterianMed. Center, New York), R. M. Sano(Advanced NMR, Woburn, MA) &P. Röschmann H

Installation of high-field NMR systems into existingclinical facilities: special considerations

H. W. Werner E The application of beam and diffraction techniquesto thin film and surface micro-analysis

Thin film and depthprofile analysis, H.Oechsner (ed.), Sprin-ger, Berlin

5-38 1984

Contents of Philips Telecommunication Review 43, No. 1, 1985

J. H. Buijs & J. H. Wolken: Field trial of a 565 Mb/s coaxialline system (pp. l-ll)

K. Brokkelkamp & F. W. J. Veerman: Electro-magnetic compatibility in Design 400-slim (pp. 12-16)

C. J. den Hollander: Third-generation higher-order digital multiplex equipment (pp. 17-30)

J. Drupsteen: A high-capacity 565 Mb/s optical system bridges long distances (pp. 31-42)

A. Wismeyer: Long-distance single-mode fibre transmission (pp. 43-49)

H. P. J. M. de Wert, V. van der Hulst, G. Kuyt & J. G. 1. Peelen: Production of single-mode fibres by the PCVD process (pp. 50-56)

F. L. van den Berg: An earth station for the EUTELSAT Multi-service System (pp. 57-68)

Contents of Electronic Components &"Applications 6, No. 3, 1984

B. Vernooij: An architectural contrast - 68000 versus iAPX 286 (pp. 130-140)

J. Seltzer & N. Siddique: Interfacing different local area networks (pp. 141-148)

G. Keitel: The KP100A monolithic pressure sensor (pp. 149-154)

G. Hine: New implosion technology to meet explosion in diode demand (pp. 155-158)

J. Exalto: HCMOS - fast but coollogic ICs (pp. 159-165)

R. E. F. Bugg: EUROM - a single-chip colour c.r.t. controller (pp. 166-177)

C. Mackenna, R. Main & J. Black: Backup support gives VMEbus powerful multiprocessing architecture (pp. 178-185)

A. Woodworth: Epitaxial diodes - rectifiers compatible with today's fast switches (pp. 186-189)

Contents of Electronic Components & Applications 6, No. 4, 1984

G. Thomsen: Disk controller supports both rigid and floppy drives (pp. 194-201)

E. Loward & P. Streit: Liquid-crystal displays for automotive applications (pp. 202-208)

'J. Nijhof: An integrated approach to CD playe;s; Part 1: The optica! pickup (pp. 209-215)

J. Nijhof: An integrated approach to CD players; Part 2: The decoding electronics (pp. 216-222)

U. Feddern & S. Zur Verth: The frame-transfer sensor - an attractive alternative to the tv camera tube (pp. 223-229)

G. Thomsen & B. Vernooij: DMA Interface for 68000 systems (pp. 230-238)

J. P. Exalto: Interfacing HCMOS with other logic families (pp. 239-245)

G. Hine: High-voltage rectifier stacks for diode-split transformer (pp. 246-252)

Volume 42, No. 2 Published 28th August 1985pages 37-68

Recent United States PatentsAbstracts from patents that describe inventions from the following research laboratories,which form part of or cooperate with the Philips group of companies:

I

Philips GmbH Forschuhgslaboratorium Aachen, WeiBhausstraJ3e,5100 Aachen, Germany A

Philips Research Laboratory Brussels, 2 avenue Van Becelaere, 1170Brussels,Belgium ' B

Philips Natuurkundig Laboratorium, Postbus 80000, 5600 JA Eindhoven,The Netherlands E

Philips GmbH Forschungslaboratorium Hamburg, Vogt-Kölln-StraJ3e 30,2000 Hamburg 54, Germany H

Laboratoires d'Electronique et de Physique Appliquée, 3 avenue Descartes,94450 Limeil-Brévannes, France L'

Philips Laboratories, N.A.P.C., 345 Scarborough Road, Briarcliff Manor,N.Y. 10510, U.S.A. N

Philips Research Laboratories, Cross Oak Lane, Redhill, Surrey RHI 5HA,&~md R

Philips Research Laboratories Sunnyvale, P.O. Box 9052, Sunnyvale,CA 94086, U.S.A. S

Supplement to Philips Technical ReviewBijlage van Philips Technisch TijdschriftNO.27

4458174Colour display tubeA. A. de KeijzerA colour display tube comprises, in an evacuated envelope, meansfor generating a number of electron beams, a display screen com-prising a large number of regions luminescing in different colourswhen struck by the beams, and colour selection means for associat-ing each electron beam with luminescent regions of one colour. Thecolour selection means includes a plurality of conductive strips anda metal plate having a plurality of parallel apertured rows. Theplate, between the apertured rows, and the strips, in the sides facingthe plate, have grooves extending in the longitudinal direction ofthe strips. The strips are accurately positioned between the rowsby insulating carriers secured in respective grooves by adhesivematerials. Each carrier engages its respective grooves in only twolocations per groove. The adhesive material, at least in the groovesof the strips, is an electrically conductive adhesive.

4481576Method of storing data in a memory of a data pro-cessing systemJ. Bicknell RWhen addressing a store cornpnsmg a plurality of low speedmemory blocks each of which can be accessed through a high speedbuffer having a limited number of memory elements, in accordancewith a pattern which is more flexible than sequential then conflictscan occur due to overloading of the memory elements. In order toavoid this, prior to storing data, the address parameters are cal-culated taking into account the read/write sequence, depth of bufferand access times and a check is made to see if there are any conflictsamong the simulated addresses. If so then a riumber of alternativemeasures can be tried in order to resolve the conflicts. Such meas-ures include the use of a small capacity, high speed vestigialmemory, adding an offset to the addresses or skipping a number ofaddresses. Once acceptable address parameters have been cal-culated then a hardware address generator can be instructed toaddress data accordingly.

July 1985

4481644Differential pulse code modulation transmission system

E J. H. Peters EDifferential pulse code modulation transmission system in whichthe transmitter and the receiver each comprise a prediction circuitfor generating a prediction signal from the transmitted DPCM-signal. This prediction circuit is in the form of two or more predic-tion channels each consisting of a non-linear network followed by aleaky integrator circuit. The inputs of these prediction channels areconnected to a common input and the output of each predictionchannel is connected to an input of a summing device, which pro-duces the desired prediction signal.

4482214Device for applying light to a linear array of magneto-opticallight switches, notably for optical printersB. Hill HG.MuchA device for illuminating a line-shaped light switching mask havinga plurality of magneto-optical light modulation elements and whichis arranged between polarizers, comprising a light source, an opticaltransmission system for transmitting as large as possible part of thelight emitted by the light source to the light switching mask, and atleast one optical body which is arranged in the light path between thelight source and the light switching mask in order to homogenizethe light distribution. The optical transmission system comprises anadapter whose entrance surface corresponds to the geometry of thelight source and whose exit surface corresponds to the geometry ofthe line-shaped light switching mask and a thin light conductorplate. The line direction of the exit surface of the adapter as well asthat of the light switching mask extends in the plane ofsaid plate.

4482954Signal processor device with conditional interruptmodule and multiprocessor system employing suchdevicesH. VrielinkE. M. A. M. van der OuderaaA. Willemse

E

Signal processor device having a processor module and' a con-ditional interrupt module for use in a multipro~.essor system,emp-

PHILIPS

loying these signal processor devices. The processor module hasaddress, data and control inputs and outputs, including an inter-rupt signal input for receiving an incoming interrupt request signal.The signal processor device has at least one conditional interruptmodule in which the identity address of the signal processor ispresent, said interrupt module having inputs for receiving an in-coming external interrupt request signal with corresponding destina-tion address. The conditional interrupt module also has compara-tors in which its identity address is compared with the destinationaddress. If the addresses agree, an interrupt signal is fed to the inter-rupt signal input of the processor module. The processor modulemayalso have an interrupt signal output and be provided with anarbitration module to prevent conflicts between several interruptrequests. The provision of the conditional interrupt module enablesinterrupts to be processed in a multiprocessor system employing aplurality of such devices without all the devices being initially inter-rupted and without it being necessary to provide a multiplicity ofinterruptlines.

4483425Vibration control systemW. S.NewmanA vibration compensation system for actively attenuating the vibra-tion of a machine. The machine has a housing, with respect to whichvibration is to be damped, and at least one body moving within thehousing. The vibration compensation system includes a counter-mass capable of being linearly reciprocated relative to the housingin a direction parallel to the motion of the moving body within themachine. A motor, coupled to the housing, drives the countermass.Elements are provided for sensing the position, or any time deriva-tive or time integral thereof, relative to the housing of the movingbody and the countermass. Control elements supply power to themotor in response to the signal outputs from all of the sensors sothat the acceleration of the countermass is in a direction oppositethe acceleration of the moving body. The magnitude of the accele-ration of the countermass is equal to the product of the accelerationof the moving body multiplied by its mass divided by the mass ofthe countermass.

4484037Ribbon-type electro-acoustic transducer with low dis-tortion and improved sensitivityJ. A. M. Nieuwendijk EW.D. A. M. van GijselA ribbon-type electro-acoustic transducer has a magnet systemwhich comprises an upper plate and a center pole between which anair gap is formed. A diaphragm on which conductors are arrangedis disposed in the air gap. The upper plate comprises two plate-shaped parts between which a space is formed in which an edge por-tion of the diaphragm is located. This results in a more homogene-ous magnetic field so that the transducer distortion may be reduced.Moreover, the transducer sensitivity is improved and is suitable forhandling signals in the mid-range audio frequency spectrum. Acavity enclosed by the magnet system and the diaphragm can beacoustically coupled via an additional cavity to a (bass-reflex) ductor an additional (passive radiator) diaphragm.

4484108High frequency ballast-ignition system for dischargelampsRH&~ NM. W.FellowsL. R. GuarneraA high frequency oscillator-inverter ballast-ignition system for adischarge lamp includes a leakage reactance transformer that formsa part of the oscillator-inverter and also couples same to the dis-charge lamp. Art impedance element electrically couples the primaryand secondary windings of the transformer in additive phase toprovide more reliable lamp ignition over a wide range of voltage andtemperature than was heretofore possible. The preheat time periodof the lamp cathodes can be better controlled by a proper choice ofthe transformer heater windings turns.

4484151Amplifier circuitA. J. NijmanF. A. C. M. SchoofsJ. F. P. van Mil

E

An amplifier circuit for supplying output voltages which are muchhigher than the breakdown voltage of the individual componentsforming the amplifier comprises a control circuit and an amplifierstage. The amplifier stage comprises 2n transistors where n is aninteger greater than one, having their main current paths seriallyconnected between two supply terminals. The bases of the transis-tors are connected to tapping points on a series chain of diodes inthe control circuit. Further supply sources apply an incrementallydecreasing sequence of voltages to the transistors so that the voltageacross any of the transistors is limited to one increment of thesequence of voltages.

·N

4484163Arrangement for biasing high-frequency active com-ponentsF. C. de Ronde LAn arrangement for applying a DC bias current to an RF activecomponent, such as a field effect transistor, serially-connected withan RF transmission line. The biasing current is supplied by a trans-mission line section connected at a junction to the transmission line.Two conductive strips, connected in parallel with the transmissionline, on opposite sides of the junction, form a band-pass filter.Each of these strips is situated at a distance from the junction whichis equal to approximately one-eighth of the wavelength of the signalfrequency transmitted on the transmission line.

4485315Blooming suppression in a CCD imaging deviceM. G. Collet EJ. G. van SantenA CCD solid state image sensor device. During the integrationperiod the surface in the image pick-up section is switched alter-nately into inversion and into accumulation. Any excess of chargecarriers which results from possible overexposure can thus bedrained by means of recombination via surfaces states.

4485357Circuit for amplitude and phase modulation of a car-rier signal by two respective input signalsJ. O. Voorman EAn electronic arrangement for generating an amplitude and phase-modulated carrier signal having a phase modulation stage with twoinputs for receiving two modulation signals, which modulationstage generates two different phase-modulated signals having thesame carrier frequency and substantially the same amplitude, andan output stage to which the phase-modulated signals are appliedfor assembling by means of summation of the phase-modulatedsignals to produce the amplitude and phase-modulated carrier, theamplitude of which is modulated in dependence on the phase dif-ference of the phase-modulated signals and the phase of which ismodulated in dependence on the sum of the phases of the phase-modulated signals.

4485392Lateral junction field effect transistor deviceB. M. Singer NA lateral junction field effect transistor device includes both a sur-face semiconductor layer located between the gate and drain con-tact regions of the device and a buried semiconductor layer whichextends beneath at least the drain contact region and the surfacesemiconductor layer of the device. The buried layer may be in theform of a continuous layer extending beneath the gate, source, anddrain contact regions of the device as well as the surface semicon-

ductor layer, or it may be provided in annular form with ah aperturebeneath the source and gate regions. The annular central buriedlayer configuration may further include an additional buried layerportion extending beneath the source region of the device. 'Deviceshaving buried and surface layers in accordance with the inventionfeature improved high-voltage breakdown characteristics, enhancedconductivity in the 'on' state, and the ability to operate in thesource-follower mode.

4485401Television system for high-definition television and atelevision transmitter and receiver suitable thereforeS. L. Tan 'EL. J. van de PolderT.M. M. KremersA compatible television system for high-definition and for standar-dized low-definition television. In a transmitter in the system, ahigh-definition video signal is generated which is split into a contoursignal which on display shows details in the horizontal and verticaldirections, and a, low-definition video signal. The low-definitionvideo signal is converted into a low-definition video signal in con-formity with the standard. The contour signal is also converted, butis transmitted periodically over several picture periods. Both theseconverted signals are transmitted or stored, respectively, in twoseparate signal channels, each suitable for standard low-definitiontelevision. In a receiver the standard video signal can be utilizeddirectly for low-definition display by a standard display device. Inaddition, a receiver comprises a high-definition display device inwhich the converted signals are reconverted and, after having beencombined result in a high definition video signal suitable for high-definition display by a picture display apparatus. As high-definitionin the region of movement in the picture may disturb the picturequality, the contour signal may be locally suppressed on display.

4486697Reversing device for a two-pole single-phase synchron-ous motorG. Diefenbach AE. KrainerA reversing device for a two-pole single-phase synchronous motorwithout a starting coil. The motor comprises a diametrically mag-netized permanent-magnet rotor having a shaft that runs againstelastic stops for reversing the direction of rotation, and a capacitorarranged in series with the stator exciter coil. The capacitor servesfor improving the reversing operation and is dimensioned so that itsreactance at the AC supply frequency is greater than the reactanceof the exciter coil of the synchronous motor.

4486716Digital FM demodulator using delay circuitsak~~ LA digital circuit for demodulating a signal which was modulated inaccordance with the relation

t

X = A sin( wot +J f(t) . dt + !/Jo),o

wherein Wo is the carrier andf(t) the modulating signal. This circuitcomprises first of all two distinct paths Which are arranged inparallel and are formed by two digital value determining stages, thefirst stage being intended to determine the values of the function

M = (I/A) cos( wot + ff(t) . dt + !/J1 'o •

which correspond to the values of the input signalof the two pathsand the second stage being intended to determine the derivative ofthe input signal for said same values of the input signal. The circuitalso comprises, at the output of these two paths, a multiplying cir-cuit for corresponding signals supplied by the first and secondstages, intended to recover a digital signal which is proportional tothe instantaneous frequency of the input signal. A clock circuitdetermines the rate of operation of the first and second stages andof the multiplying circuit.

4486758Antenna element for circularly polarized high-fre-quency signalsF. C. de Ronde LAn antenna element for coupling circularly-polarized radiation to afeedline. The element includes a pair of superposed planar dielectriclayers. An outer surface of each layer is covered with an electrically-conductive layer forming a ground plane and having a circularopening defining respective cavities. Orthogonally-crossed dipolesare disposed between the dielectric layers and adjacent the openingsfor coupling radiation to the feedline through striplines also dis-posed between the dielectric layers.

4486878Digital telephone exchange with means for processingpacket-switched dataG. M. J. Havermans EDigital telephone exchange compnsing a plurality of peripheralcontrol domains which are either connected to a digital trunk net-work or are directly interconnected. Each domain comprises severaldigital subscriber interface units, a group of digital subscriber setsbeing connected to each interface unit. The transmission of infor-mation over the subscriber line is effected in a b-channel for speech(64 kb/s) a b '-channel for circuit-switched data (0/8/64 kb/s) and a8-channel for packet-switched data (8/16 kb/s). The subscriber lineinterface circuits comprise means for identifying the pack et-switched data signals and to apply them to a packet processing unit.In this unit the packets are distinguished as firstly signalling infor-mation and secondly telemetry and slow data. The separately ap-plied signalling information and telemetry data and slow data in-tended for a subscriber line are combined by the packet processingunit to form one packet-switched data signal for the subscriber line.In a data unit connected to the trunk network the signals combinedinto messages are exchanged between the subscribers without load-ing the central control unit of the telephone exchange.

4486882System for transmitting binary data via a plurality ofchannels by means of a convolutional codeP. M. O. A. Piret B, ET. KrolA system for correcting multiple simultaneously erroneous chan-nels within a plurality of parallel data channels including redundantchannels. At the receiving side a group of syndrome generatorseach applies a secondary parity check matrix for producing corres-ponding groups of syndrome bit streams. If the error is correctable,one or more of the syndrome bit streams is added to correspondingcode bit streams. If a syndrome bit stream indicates an error in anon-applicable code bit channel, or otherwise indicates too manyerrors, it remains unused. Decoders with feedback (restoration ofsyndromes after correction) and feedback-free decoders are pos-sible.

4487817Electrochemical cell comprising stable hydride-form-ing materialJ. J. G. S. A. Willems EJ. R. G. C.M. van BeekK. H. J. BuschowAn electrochemical cell having a negative electrode comprising acompound derived from LaNi5, in which La is optionally sub-stituted by a plateau pressure-increasing element and in which Niis substituted entirely or partly by a plateau pressure-reducingelement, for example, Co and/or Cu, with the object of consider-ably reducing volume steps and hence crack formation of the inter-metallic compound during charging and discharging. Moreover,the corrosion of the intermetallic compound is counteracted byadding small quantities of AI, Cr and/or Si, which metals enhancethe formation of a protecting oxide layer.

4488277Control system for an optical data recording apparatusR. McFarlane NG. C. KenneyA closed loop control system for an optical recording apparatus ofthe read after write type comprises a comparator for comparing theinput data signal with a playback signal derived from the read beamwhich trails the write beam and is modulated by the data patterninscribed on the recording medium by the write beam. The errorsignal generated by the comparator is applied to a controller whichvaries the modulation of the read beam in dependence on the errorsignal, for example, by modifying the data signal used to drive thewrite beam modulator. In this way, the control system compensatesfor nonuniformities in the recording medium and the like so as toensure that. the pattern inscribed by the write beam accurately re-presents the data to be stored.

4488789Electromagnetically deflectable deviceG. C.KenneyAn electromagnetically deflectable device includes a mirror pivotallymounted to a support by means of a silicone based resilient element.An 'electromagnetic deflection coil is fixed to the mirror underside.The coil lead wires are embedded in the resilient element and passthrough the element to the support.

4489050Method of preparing a hydrogen-absorbing alloyR. M. van Essen EK. H. J. BuschowAlloys consisting of from 64 to 77 atomic percent of manganesewith the remainder zirconium are not suitable without further pro-cessing as a material for storing hydrogen at technically desiredpressures. This property can be advantageously influenced by a heattreatment until a homogeneous Cl4 type of Laves phase has beenobtained.

4489338Memory cell with thick oxide at least as deep as chan-nel stopW. G. Voncken EIn a dynamic memory cell, the mutual cross-talk is considerablyreduced by providing a diffused selection line below a layer of thickoxide (for example, LOCOS). As a result of this the capacitivecoupling with other selection lines is considerably reduced, as isthe capacity of the selection line with respect to channel stoppingregions provided between the memory cells,

4489357Magnetic sensor having multilayered flux conductorsJ. A. C. van Ooijen ER. D. J. VerhaarA magnetic sensor includes a magneto-resistive element which mag-netically bridges a gap between two magnetic flux conductors, Inorder to reduce the noise level and higher harmonic distortion ofthe sensor, each of the flux conductors includes at least two layersof magnetically permeable materials having substantially the samecomposition between which a layer is present which has a differentcomposition.

4489480Method of manufacturing field effect transistors ofGaAs by ion implantationG. M. Martin LS. Makram-EbeidC. VengerThe invention relates to a method of manufacturing field effect tran-sistors of gallium arsenide obtained by ion implantation of light

donors, such as silicon or selenium, in a semi-insulating substrateof gallium arsenide. In order to reduce out-diffusion of the deeplevel responsible for parasitic phenomena in the operation of thetransistors, the method is characterized in that in addition oxygenions are implanted in at least the region of the substrate intended toform the channel region of the field effect transistor. After implan-tation, the substrate is sintered at a temperature between 600 and900 "C in either an enveloping substance or uncovered, and/or in anatmosphere of arsine.

4490163 'Method of manufacturing a fiber-optical couplingelementC. M. G. JoehemG. D. KhoeA. J. A. Nicia

E

N

A method of manufacturing a fiber-optical coupling element byfusion of two monomode fibers. The fiber cores are made of a coreglass, the American softening temperature of which is at least 80°Chigher than that of the cladding glass. The fibers are heated to atemperature between 520 and 560 °C. By the method, fibers can befused to form a coupling element without undesirable deformationof the fiber cores.

4490264Device incorporating a bearingJ. GerkemaA. R. MiedemaBearings can be lubricated with ductile metal films, It has beenfound that the service life of such lubricating films can be improvedby the use of metals which are alloyed with a component having ahigher surface tension than the metal.

E

4490605Photoelectric detection structureP. DolizyF. Grolière

L

The photoelectric device comprises a photosensitive layer on a sub-strate which is transparent to' incident radiation. An intermediatelayer for optically adapting the photosensitive layer to the substrateis provided therebetween. The respective thicknesses of the inter-mediate layer and the photosensitive layer are proportioned so thatphoton absorption takes place in the photosensitive layer near theoutput of the layer within a distance on the order of magnitude ofthe escaping depth of the electrons. Photon absorption takes placein such manner that the efficiencyof the photoemission of the struc-ture is optimum taking into account the nature of the materials ofthe layers.

4490695Wideband power adder-divider for high-frequencycircuits and impedance transformer realized on thebasis of the adder-dividerF. C. de Ronde LA wideband power adder-divider for high-frequency circuits in-cluding a first conductive transmission line for passing a high-fre-quency current, second and third conductive transmission lines overwhich this high-frequency current is distributed, and a conductivewedge-shaped transition section joining the first to the second andthird lines. This section has t\VOarc-shaped outer edges which aretangentially connected at one end of the section to the first line andat the other end to the second and third lines. The section includesparallel slots extending transversely to the direction of propagationof the current. The parallel slots have ends which are separatedfrom the arc-shaped edges by a distance which is less than the widthof the second and third transmission lines.

4490714Digital-to-analog converter for bipolar signalsR. J. van de P!assche EE. C. DijkmansIn a digital-to-analog converter for bipolar signals all the bitschange when the signals pass through the zero level. This results ina poor signal-to-noise ratio owing to the small signal and the largenoise contribution by the switching transients. The invention pro-poses to add a digital number to or subtract it from the digital inputsignal as an offset. As a result of this, the switching point is shiftedtowards a higher amplitude, which improves the signal-to-noiseratio and the distortion in the case of digital audio signals.

4490839Method and arrangement for sound analysisE.Bunge HFor sound analysis, especially for speaker identification, a long-term spectrum is often formed from the recorded signal and com-pared to a long-term spectrum of a previously recorded signal.When the signal is, for example, received over telephone lines thetransfer function thereof may distort the received signal to such anextent that identification is impossible. It is now proposed not touse the long-term spectrum for identification but rather its change,that is to say to accumulate the difference between two consecutiveshort-term spectra or the difference between such short-term spec-trum and the long-term spectrum and to divide this accumulatedvalue by the long-term spectrum in a Divider. Since the numeratorand denominator each contain the frequency-weighting factor ofthe telephone line transfer function, this factor is effectivelycancelled out by virtue of the division operation performed in theDivider thereby eliminating the effect of the unknown transferfunction. As a result the influence of the transfer function of thetransmission path disappears almost completely.

4490906Shaving apparatusF. HaesC. M. ReynhoutA shaving apparatus is provided with a shear plate having hair-entry apertures and formed with an inner surface, and a cutting unitassociated with and drivable relative to the shear plate. The cuttingunit comprises cutting elements extending towards the shear plate,each cutting element having an end surface facing the inner surfaceof the shear plate and being formed with a cutting edge, and hair-pulling elements respectively associated with the cutting elementsand positioned in front of the cutting elements in the direction ofdriving, each hair-cutting element being rigidly connected to its as-sociated cutting element and. having a first end surface portionfacing the inner surface of the shear plate and being formed with acontact edge. Each contact edge is situated at a greater distancethan its associated cutting edge from the inner surface of the shearplate. Each hair-pulling element also has a second end surface por-tion adjoining the first end surface portion but situated at a greaterdistance than the first end surface portion from the inner surface ofthe shear plate to thereby provide a recess between the end surfaceof each cutting element and the first end surface portion of its as-sociated hair-pulling element.

4491529Heat accumulating agentV.Pie!J. SchröderThe use of calcium chloride hexahydrate as a heat accumulatingagent for latent heat accumulators is improved when as a nucleatingagent (so as to avoid supercooling) special caesium salts, bismuthsalts and/or lead salts are used.

4491743Voltage translatorD. D. Smith SA bipolar voltage translator contains a pair of differentially coupledtransistors for converting an input voltage supplied to one of thepair into an output voltage taken between the other and a first resis-tor. A further transistor coupled through a second resistor.to a volt-age supply VEE provides current for the differential pair. A voltagereference circuit containing at least three serially coupled diodeswith a resistive voltage divider across an intermediate one of thediodes provides the current-source transistor with a reference volt-age that equals VEE + (1+ a)VBE where a is 0.2-3.0. The ratio ofthe first resistor to the second is desirably PIa where P is the outputvoltage swing divided by VBB. IfPis 1 and the transistors are NPNdevices, the output voltage level is suitable for current tree logic.

4491860TiW2N fusible links in semiconductor integrated cir-cuits . . .

~C.P.Lim SA film of titanium-tungsten nitride is used to provide the dual func-tion of a fuse link between a semiconductive device and an inter-connect line in a memory array and of a barrier metal between an-other metal and a semiconductor region.

4492426Optical branch couplerA. J. A. NiciaC. J. T. Potters

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An optical branch coupler comprising a semi-transparent mirrorwhich is tiltable about an axis which is situated substantially in theplane of the mirror and substantially parallel to the plane déterrninedby the directions of the transmitted and the reflected light beams. Awall toward which the reflected beam is directed is adjustable aboutan axis which is at right angles to the plane of the light beams.

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4492721Method of providing magnesium fluoride layers~Hkw~ ~T. J. A. PopmaH. J. P. NabbenH. A. M. van Ha!J. HaismaMagnesium fluoride layers are obtained by disproportionation offluorine-containing organic magnesium compounds, notably mag-nesium trifluoroacetate, magnesium trifluoroacetylacetonate andmagnesium hexafluoroacetylacetonate. A solution of such a com-pound is provided on the substrate in an organic solvent by spinningor dipping at room temperature after which the layer is heated to500 oe. The solution mayalso be atomized and sprayed on the sub-strate which is maintained at a temperature of 600 °C. It is possibleby means of this method to provide pure magnesium fluoride layersat a comparatively low temperature in air and without using filmforming vehicles. The MgF2 layers obtained according to saidmethod are useful as antireflective layers on display screens, onoptical elements and as components in a multilayer packet, forexample a dichroic mirror.

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4492967Optical recording discD. J. Broer.A. W. de PoorterOptical recording disc having a supporting plate of synthetic resinor being coated with a layer of synthetic resin, an ablative recordinglayer on the synthetic resin or the layer of synthetic resin and aphosphorus derivative having at least one organic radical in theinterface of the synthetic resin or layer of synthetic resin on the sideof the recording layer.

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4492976Line standard conversion circuit for a television signalM. C. W. van Buu/ EJ. G. RavenW.H. C. A. van de VenA television receiving system for converting a video signalof oneline standard to a video signalof another line standard. A fielddelay circuit is provided which separates the 'video signalof the oneline standard into a high frequency and low frequency portion. Thelow frequency portion of the signal is processed to have a delayduring one field different from the delay of a subsequent field. In-dependent processing means for the high frequency portion of theseparàted signal is provided. The processed high frequency and lowfrequency signals are combined to provide a video signal for con-verting to a different line standard. By processing the high fre-quency and low frequency portions of the video signal differently, asavings in hardware components is realized without material degra-dation in performance.,

4493099FM broadcasting system with transmitter ldentiûcatlonJ.M. Schmidt EAn FM broadcasting system comprises an FM transmitter for trans-mitting a multiplex signalwhich is frequency-modulated on a maincarrier wave and an FM receiver for cooperation with said FMtransmitter. The multiplex signal comprises: an audio-frequencyfirst information signal and, in the case of a stereo transmission, asecond information signal modulated on a suppressed stereo sub-carrier, a stereo pilot signal whose frequency (jp) is situated be-tween the frequency spectra of the two information signals, a firstbinary-code signal (Jp - je) which is phase-modulated on a firstcode subcarrier situated outside the frequency spectra, which codesub carrier is a harmonic of a subharmonie of the stereo pilot (jp)which harmonic does not coincide with a harmonic of said pilot(jp), the multiplex signal, in ,order to extend the transmissioncapacity, comprising a second 'binary-code signal which is phase-modulated on a second code subcarrier (jp +je). The carrier waveinformation of the two code subcarrier waves can be identified in asimple way by selecting their frequencies to be symmetrical aboutthe stereo pilot signaI or its harmonic (3jp) and by selecting thephase angle between the sum. of the two code subcarriers and thestereo pilot or the relevant harmonic thereof to be situated at pre-ferably an integral multiple of 71/4.

4493365Heating device with heat storageF. OrtegaA heat storage device comprises a hermetically sealed metallic con-tainer having one or more molten alkali metal fluorides and/oralkaline earth metal fluorides included therein. A material having acarbon basis is also included in the metallic container to react withany oxygen present in the metallic container and thereby preventcorrosion of the metallic container by the molten fluorides.

4493887Optical recording elementW.L. PeetersJ. J. PonjeéJ. W.D. MartensOptical recording element cornpnsmg a transparent supportingplate which on one side has successively a recording layer of prefer-ably a ferrite, an optional transparent intermediate layer and areflecting optical structure of reflection areas which are situatedalternately at a high level and at a lower level and which can be readoptically. '

4494031High power acoustic wave arrangements with N2

parallel-series connected acoustic wave devicesC.S.Barnes RP.A. MooreP.D. WhiteN2 acoustic wave devices with substantially the same electrical im-pedance and transfer characteristics at a given operating frequencyare electrically connected in a parallel-series arrangement which hassubstantially the same electrical impedance and transfer character-istics as anyone of the individual N2 devices, but an increasedactive device area. The increased active area reduces stress and alle-viates acoustically-induced migration in the metal of, for example,transducer electrode fingers of resonators at high power levels. Theparallel-series arrangement consists of N groups, each of whichcomprises N devices, the corresponding pairs of terminals of whichare connected in series. Some terminals may be common to two ormore devices and some devices may have merged transducers inwhich the electrode fingers of one transducer are a longitudinal ex-tension of the fingers of a parallel transducer. In the case of muiti-port devices the input and output terminal pairs may be differentlygrouped as regards the individual devices to which they belong,

4495221Variable rate semiconductor deposition processE. K. Broadbent SA layer of a conductive material consisting of aluminium alone orin combination with a small percentage of copper and/or silicon isformed on a semiconductor surface in a two-step deposition pro-cess in such a manner as to largely avoid serious continuity defectsin the layer.

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4495412Device for the optical scanning of a documentM. L. G. Thoone E, A, BG.D.KhoeD.KüppersP. A. G. J. GustinThe device comprises a transducer comprising a row of photoelec-tric elements, and a coupling member with an entrance which is tobe directed towards the document and an exit which is coupled tothe transducer. The coupling member is constructed as an inte-grated optical waveguide circuit comprising a glass substrate inwhich there are provided grooves which, in order to form opticalconductors, are filled with a glass having a refractive index which ishigher than that of the glass of the substrate. The width of eachgroove gradually decreases from the entrance of the coupling mem-ber towards the exit and over the entire length of the grooves thedistance between every two adjacent grooves is substantially con-stant and substantially smaller than the width of the grooves, sothat substantially all light originating from a scanned line of thedocument is supplied to the transducer.

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4496202Device for high voltage transfer between two partswhich are rotatable relative to each otherF. K. Beckmann HT. He/ze/H. PeemöllerThe invention relates to a high voltage transfer device comprisingtwo insulator bodies which are rotatable with respect to each other.In each insulator body there is embedded an electrode arrangementwhich .horizontally encloses the axis of rotation. The two electrodearrangements together form a kind of Faraday cage, so that thefield between the two electrode arrangements and in their vicinity iscorrected and reduced.

4497699Method of treating foil for electrolytic capacitorsH. J. de Wit EA. W.M. van BerloC. CrevecoeurA method of treating foil for use in electrolytic capacitors in whichthe foil moves in one direction through a treatment liquid and inwhich the capacitance is measured continuously by means of atleast one current-carrying electrode from which alternating currentis conveyed and at least one voltage electrode at a small distancefrom the foil. The foil capacitance is measured by means of a phase-sensitive voltmeter. The measured capacitance is used to control thetreatment method, etching or forming. In a preferred embodimenttwo current-carrying electrodes are present on either side of the foiland two voltage electrodes are present between the current-carryingelectrodes and the foil on either side thereof. This avoids contactingof the foil.

4498111Method and apparatus for recording or reproducingstereophonic information in a magnetic record carrierA. M. A. Rijckaert EA. WalravenIn accordance with a method of recording and/or reproducingstereophonic information in two adjacent tracks of a magneticrecord carrier, an auxiliary signal whose frequency content issituated outside the frequency spectrum of the stereophonic infer-mation is recorded in the tracks and in the magnetic record-carrierarea between the tracks during recording. During reproduction, theauxiliary signals read from the record carrier by the two transducersare used to control the gain of a pair of variable amplifiers so as toensure that the amplitudes of the stereophonic information signalsthus reproduced are independent of tracking errors.

4498296Thermodynamic oscillator with average pressure con-trolK. Dijkstra EA. J. GarenfieldA thermodynamic oscillator having a displacer and a piston (furtherdisplacer) movable due to pressure fluctuations at the resonancefrequency of the oscillator. The displacer and the piston are locatedin a working space which is filled with working medium and can beconnected through a release valve and a supply valve, respectively,to a simple reservoir filled upon working medium with an increaseand a decrease, respectively, of the ambient temperature with res-pect to a nominal temperature. The valves have an opening pressurewhich is a function of the ambient temperature. The average pres-sure and the resonance frequency of the oscillator can thus be stabi-lized at a variable ambient temperature. The oscillator can beoperated as a cold-gas engine, a hot-gas engine (motor), a heatpump or a current generator.

4499011Resistance paste for a resistor bodyA. H. BoonstraC. A. H. A. MutsaersF. N. G. R. van der KruijsA resistance paste for the manufacture of a resistor body, forexample, by silk-screening and the resistance body manufacturedherewith, which paste comprises a mixture of Pb2RhxRu2_x07_y, apermanent binder and a temporary firable binder. In the formula0.15 ;;;;x;;;; 0.95 and 0;;;; y;;;;!. The resulting resistor body inthe temperature range of from - 55 to + 150 °C has a tempera-ture coefficient of the resistance between -10 x 10-6 IOC and+ 10X 10-6 IOC and is very stable. The resistance variation duringthe life of the resistor is smaller than ± 0.5OJo.

4499177Method of manufacturing a semiconductor deviceF. A. Vollenbroek EE. J. SpiertzA method of manufacturing a semiconductor device in which aphotosensitive lacquer layer is developed in a lye solution, and com-prises a polymeric material and a sensitizer with a diazo group anda ketone group. This lacquer layer is formed on a substrate surface.After a patterning irradiation, but before development, the lacquerlayer is subjected to an intermediate treatment comprising two ir-radiations. These irradiations result in that differences in solubilityin lye are obtained in the direction of thickness in the parts of thelacquer layer which were not exposed during the patterning irradia-tion. In this manner, it is possible to realize lacquer patterns withdifferent profiles. .

4499521Low-fire ceramic dielectric compositions for multi-layer ceramic capacitorsR. T.McSweeney NS.A.LongA Iow fire ceramic dielectric composition, a multilayer capacitormade from such a ceramic dielectric composition provided withsilver/palladium electrodes having at least 65 atomic percent silver,and a method of manufacturing such a multilayer capacitor. Theceramic is barium titanate-based and includes Bi20s, Nb205 andTi02 to improve sinterability. MnCOs is added to increase theinsulation resistance. The multilayer capacitor includes high silver-content electrodes to reduce the quantity of expensive noble metals.The multilayer part may be fired at a temperature of 1150 °C or lessto yield a capacitor meeting EIA specification X7R. The Iow firingtemperature also inhibits a chemical reaction between bismuth andpalladium.

4499524High value surface mounted capacitorL. J. Shioleno NA high value surface mounted capacitor assembled from a gangedassembly of multilayer ceramic capacitors adapted to fit within apackage which may be either surface mounted or pin mounted, saidpackage being shaped for handling by automatic insertion equip-ment.

4499540Device for the testing of bodies comprising periodicstructuresG. Kowalski HThe invention relates to a device for testing a body which comprisesperiodic structures. The device includes an image forming devicefor determining measurement signals representing the periodicstructures, and a further electronic device. This electronic deviceforms the frequency spectrum from neighbouring measurementvalues in the direction of the periodic body structures, suppressesthe fundamental and higher harmonics of the periodic structures inthe relevant spectrum, and retransforms the spectrums thus modi-fied for application to an image evaluation device.

E 4499570Dropout circuit arrangement for converting an infor-mation signal into a rectangular signalK. A. Schouhamer lmmink ER. M. A artsFor the conversion of a signal .read from a record carrier into arectangular signal, a threshold-value circuit is used, whose thresh-old value is determined by a reference signal. The reference signal isderived from a d.c. 'component in the converted signal. During adropout in the signal being read, the reference signal is maintainedat the level which it had before the occurrence of the dropout.

4499574Record carrier with an optically readable informationstructureJ. J. M. Braat EA record carrier is described having an optically readable informa-tion structure comprising trackwise arranged information areaswhich, in the track direction, alternate with intermediate areas, theinformation being contained in at least the locallength of the infor-mation areas, of which information structure the average length ofthe information areas varies. It is demonstrated that by adaptingthe track period to the average length of the information areas inthe tracks, the cross-talk between the tracks may be reduced with-out essentially reducing the information density.

4500825Self-starting single-phase synchronous motorH. Schemmann HL. BertramA self-starting single-phase synchronous motor without an auxiliarycoil comprises a diametrically magnetized permanent-magnet rotorand a two-pole stator provided with exciter coils. A PTC resistor isarranged in the circuit of the exciter coils. The PTC resistor is pro-portioned so that its resistance will increase to a continuously per-missible load resistance value after approximately 0.5 to 1 sec.

4501016Device for the dynamic adjustment of a black/whitediserimination threshold for the processing of imagescontaining grey valuesE. H. J. Persoon ER. M. S. S. AbeysekeraA device for binarizing an image consisting of grey values by meansof a dynamically adjusted black/white discrimination thresholdcomprises: a. a generator for determining a discrimination thresh-old each time for a first local sub-set of pixels; b. an edge detectorfor determining a local edge between darker and lighter pixels froma second local sub-set of pixels, associated with a first local sub-setof pixels, in order to form an accept signal, and otherwise a rejectsignal; and c. a discriminator for presenting, on the basis of a greyvalue and the relevant discrimination threshold, alternatively ablack or a white signal.

4501967Broad band pyroelectric infrared detectorA. ShaulovAn infrared thermal detector includes an infrared thermal sensingelement, a load resistor, and a voltage supply means. The infraredthermal sensing element is a pyroelectric material whose electricalconductivity changes with temperature. The circuit and deviceparameters are chosen such that the detector will have a frequencyresponse over a broad band from dc to a high frequency determinedby the electronic time constant of the circuit. The detector thus hasall the advantages of either a pyroelectric detector without a chop-per, or a thermistor bolometer having a fast response time.

4502017Operational amplifier having frequency compensationR. J. van de Plassche EE. C. DijkmansAn operational amplifier with frequency compensation is described.The amplifier includes a first amplifier with a low-impedance outputfollowed by a transconductance amplifier with a capacitive feed-forward. The transconductance amplifier is followed by a Millerintegrator.

4502019Dynamic amplifier circuitA. H.M. van Roermund EA dynamic amplifier circuit, specifically for switched-capacitor fil-ters, having a current source which supplies an exponentially-de-creasing bias current. In addition, a current source is included forsupplying an additional bias current in order to define the minimumbias current in the amplifier circuit.

4503346Electric motor having a stator iron of a bent shapeL. Bertram HH. SchemmannElectric motor, in particular series-, split-po le- and single-phasesynchronous motor, having a bent stator iron, pole shoe shanksformed by the stator iron which form pole shoes at their free ends.Induction coils are provided on the pole shoe limbs. A rotatable,radially magnetized permanent magnetic rotor is present betweenthe pole shoes. In this electric motor the oppositely located poleshoes are formed at the end faces of the pole shoe shanks. The rotorshaft intersects the central longitudinal line of the two pole shoeshanks. Finally, the parts of the pole shoe shanks facing away fromthe pole shoes are bent and interconnected in the form of a bridge.

4503482Ceramic dielectric based on bismuth-containing BaTi03D. Hennings AH. SchreinemacherCeramic dielectric based on bismuth-containing BaTiOs in the formof a monophase mixed crystal-ceramic in which 0.02 to 0.12 mol ofthe layer perovskite PbBi4Ti4015 or SrBi4Ti4015 per mol of BaTiOsare provided. On account of its comparatively low sintering tempe-rature and in particular on account of the very small change of thevalue of the relative dielectric constant with applied direct voltagefields, the ceramic is particularly suitable for the manufacture ofmultilayer capacitors.

4504111Method of multiplexing transmission channels in astep-index optical fibre and device for carrying out themethodJ. J. Hunzinger L

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An optical multiplexer wherein a plurality of channels are formedin a step index optical fibre by groups of light rays which propagatealong the fibre by consecutive total reflections at the core/claddinginterface. The rays are grouped depending on their angle with thefibre axis so that for each channel, at any point of the fibre, the raysof a given group are situated between two cones whose commonapex is formed by that point and which are rotationally symmetricalabout a common axis parallel to the fibre axis. The cones define theportion of the angular aperture relating to each channel. The aper-ture portions relating to all the channels are moreover juxtaposed.A multi-axial optical system directs each of a plurality of light sig-nals along a region defined by the cones so as to inject the light sig-nal into the aperture portion of the associated channel for eachchannel at the fibre input and reception means which are specific ofthe aperture portion of said channel at the output.

4504574Method of forming a resist mask resistant to plasmaetchingJ.Meyer RD. J. VintonA mask which is resistant to a .plasma etching treatment is formedby lithographically patterning a radiation sensitive film present on asubstrate. The etch resistance of the mask is enhanced by exposureto a carbon monoxide plasma which forms a region with an en-hanced etch resistance over the surface of the patterned film. Thismethod may be used, for example, to manufacture a photomaskusing a chromium coated glass substrate, or during the manufac-ture of semiconductor devices on a semiconductor wafer substrate.