TRANS WORLD COMMUNICATIONS, INC. • A Subsidiary of Datron Systems, Inc.

TW5201REMOTE CONTROL UNITOPERATOR'S MANUAL

(",aNS\Nor=tLLJ rMfor communications

Manual Part No. 1W5201-MSOPPublication #991426Printed: April 1987

304 Enterprise StreetEscondido, CA 92025, U.S.A.

Phone (619) 747-1079, Telex 695-433Fax (619) 741-1658

WARRANTY

Trans World Communications, Inc. (TWC) warrants that new TWC equipment has been manufacturedfree of defects in design, material and' workmanship. If the equipment does not give satisfactory servicedue to defects covered by this warranty, TWC will, at its option, replace or repair the equipment free ofcharge.

The warranty is for a period of 90 days from the date of installation. In the event that the equipment isnot installed within 90 days of factory shipment, satisfactory evidence of the installation date must besubmitted.

LIMITATIONS:

This warranty does not cover physical damage caused by impact, liquids or gases. Defects caused bylightning, static discharge, voltage transients, or application of incorrect supply voltages are specificallyexcluded from this warranty.

RETURN OF EQUIPMENT· USA:

The equipment shall be returned freight prepaid to the Service Department, Trans World Communications,Inc., 304 Enterprise Street, Escondido, California 92025. The equipment should be packed securely, asTWC will not be responsible for damage incurred in transit Please include a letter containing the follow­ing information:

1. Model, serial number, and date of installation.2. Name of dealer or supplier of equipment3. Detailed explanation of problem.4. Return shipping instructions.

TWC will return the equipment prepaid by United Parcel Service, Parcel Post or truck. If alternate ship­ping is specified, freight charges will be made collect.

RETURN OF EQUIPMENT· FOREIGN:

Write for specific instructions. Do not return equipment without authorization. It is usually not possibleto clear equipment through U.S. Customs without the correct documentation. If equipment is returnedwithout authorization, the sender is responsible for all taxes, customs duties and clearance charges.

LIMITED PARTS WARRANTY:

This warranty shall cover all parts in the equipment for a period of 12 months from the date of installa­tion, subject to the previous conditions and limitations. The parts will be replaced free of cost. The laborcharges will be made at the current TWC hourly service rate.

PARTS REPLACEMENT:

If it is not practical, or the purchaser does not want to return the equipment to the factory, this warranty islimited to the supply of replacement parts for a period of 12 months from the date of equipment installa­tion. The following instructions for the supply of replacement parts should be followed:

1. Return defective parts prepaid to: Parts Replacement, Trans World Communications, Inc., 304Enterprise Street, Escondido, California 92025.

2. Include a letter with the following information:a) Part number(s).b) Serial number and model of equipment.c) Date of installation.

Parts returned without this information will not be replaced. In the event of a dispute over the age of thereplacement part, components date coded over 24 months prior will be considered out of warranty.

1.11.2

1.3

1.4

2.1

2.2

2.3

2.4

2.5

3.1

3.2

3.2.1

3.2.2

3.2.3

3.2.4

3.2.5

3.2.6

3.2.7

3.2.8

3.2.9

3.2.10

3.2.11

3.3

3.3.1

3.3.2

3.4

3.5

3.6

3.7

3.7.1

3.7.2

3.7.3

3.8

3.9

3.10

3.11

TABLE OF CONTENTS

SECTION 1 • GENERAL INFORMATION

Introduction .1-1

Control Signalling .1-1

Transceiver Response .1-1

Technical Specifications .1-1

SECTION 2 • INSTALLATION

Transceiver Connections ; 2-1

Power Suppl y 2-14 Wire to 2 Wire Conversion 2-1

Balance Check, 2 Wire Systems Only 2-2

DC Keying Option Instructions 2- 2

SECTION 3 • OPERATIONIntroduction 3-1

Front Panel Controls 3-1

Power On/Off, Audio Gain Control 3-1

Remote/Local Control Selection 3-1

Speaker On/Off 3-1

Squelch On/Off 3-1Mode Switches 3-1

Automatic Antenna Tuner Control 3-1

External Amp On/Off 3-1Scan Mode Initiate Button 3-1

Up/Down Tuning Buttons 3-1Selective Call Buttons 3-1

Keypad .......................................................................................................................•. .3-1Front Panel Indicators 3-1

Frequency Display 3-1

Loudspeaker 3 -2Front Panel Connector 3-2

Channel Frequencies.; 3-2

Operation -- Memory Channel Selection .3-2

Operation -- Free Tune Channel 3-2

Programming the Free Tune Channel 3-2

Programming the Free Tune Channel for Half-duplex Frequencies .3-2

Re-Calling the Free Tune Channel 3-2

Fine Tuning the Transceiver 3-2

Operation -- Scan Mode 3-2

Operation -- Selective Call 3-3CW Sidetone 3- 3

4.1

4.2

4.3

1-1

2-1

2-2

2-3

2-42-5

2-6

3-1

1-1

SECTION 4 • OPERATING NOTES

Answer-Back 4-1

MIC GAIN" Adjustment 4-1

"Watchdog" Timer 4-1

FIGURES

Remote Control Unit 1-0

Control Cable - Remote Control to TWlOO Transceiver 2-1

Control Cable - Remote Control to RTlOOfMP Transceiver 2-2

Power. Transformer Connection 2- 3Remote Control Rear Panel 2-3

Component Location Diagram, Frequency Control Module, M9MP 2-4

Component Location Diagram, Control Head 2-5

TW5201 Remote Control - Front Panel Control 3-3

TABLES

Technical Specifications 1-1

ii

This page intentionally left blank.

III

FIGURE 1-1.Remote Control Unit.

1-0

SECTION 1GENERAL DESCRIPTION

1.1 INTRODUCTIONThe Remote Control is an audio-dependent control systemwhich allows great physical separation from the transceiv~ing equipment to the operating point. The unit may beused over any full-duplex (continuously bi-directional)audio link; including a twisted pair (supplied), goodquality leased line, microwave link, etc.

1.2 CONTROL SIGNALLINGThe Remote control achieves its control signalling usingan AFSK data transmission standard -- Bell 103, and runsat 600 Baud. A microprocessor at the control head inter­prets the various functions and commands, and translatesthem into serial databursts. The data bursts are then

futher translated into audio tones and sent over thetwisted pair (or other link) to the transceiver.

1.3 TRANSCEIVER RESPONSE

The transceiver has the same data capability, and when itreceives the data burst, puts out an answer-back to let thecontrol head know that it was received correctly. This"ARQ" type of system ensures that the control headshows only valid information.

1.4 TECHNICAL SPECIFICATIONS

Table 1-1 defines technical specifications of the RemoteControl.

REMOTE INTERFACE:

TRANSCEIVER INTERFACE:

LINE LEVELS:

DATA TRANSMISSION MEDIUM:

DATA FORMAT:

CONTROLS:

DISPLAY:

AUDIO:

DISTORTION:

MICROPHONE INPUT:

TRANSIENT PROTECTION:

POWER SUPPLY:

TEMPERATURE RANGE:

SIZE:

WEIGHT:

TABLE 1-1.

Technical Specifications.

2 wire line, 600n nominal, bidirectional, or 4 wire unbalanced.

4 wire unbalanced (standard), or 2 wire 600n line, RS-232IN/OUT (optional).

-10 dBM to +3 dBM.

AFSK, U.S. standard tones.

ASCII, 600 Baud, 8 bits, no parity, one stop bit, withasynchronous simplex acknowledgement system sent in fourbyte bursts.

12 key Keypad (Channel, Frequency, Selective Call Code),

Audio Gain, Mode (USB, LSB), AM (On/Off), Squelch(On/Off), Coupler rune Initiate, Scan (On/Off), Selective CallSelect, Selective Call Initiate, Frequency Step Up/Down,Amplifier (On/Off), Speaker (On/Off), Option, CWo

Liquid Crystal (Channel Number, Frequency, SelectiveCalling Code, Link Status).

Internal Loudspeaker, 2 W output.

Less than 5%.

Low impedance dynamic, internal gain control and VOGAD.

Metal Oxide Varistor, 2 wire systems.

12 Vdc@ 1 Amp max., 110/220 Vac, 50/60 Hz 25 VA.

-30°C to +550C

34.3 cmW x 12.7 cmH x 15.9 cmD (13.5" x 5" x 6.25")

2.84 kg (6.25 Ibs)

Specifications subject to change without notice.

1-1

l

SECTION 2INSTALLATION

2.1 TRANSCEIVER CONNECTIONS

Use the control cable provided to connect the control headto the transceiver. Figure 2-1 shows the standard 10 metercontrol cable used between the TW5201 and the TWl00transceiver. Plug the 9-pin transceiver connector into J9on the transceiver, and insert the small connector into thecontrol head. Figure 2-2 shows the control cable used be­tween the TW5201 and the RTlOO/MP transceiver. Plugthe 8-pin transceiver connector into J2 on the radio rearpanel.

If more than 10 meters of connecting cable are required asplice may be made, or a good voice-grade, leased linemay be obtained for the purpose if the 2-wire system isused. Conventional telephone lines may not be suitablefor use with the remote, since harmonic and other un­desirable distortions may be present in unknown quantity.The poor balance of such phone lines also detracts heavilyfrom system performance.

mains. If it is necessary to change the mains voltage, care­fully remove the eight screws holding the top cover as­sembly. Gently lift up on the cover and rock it forward,resting it on the front face of the panel.

Observe the power transformer on the left and refer to Fig­ure 2-3 for the desired strapping arrangement.

When using an external DC supply, make sure the ACcord has fIrst been disconnected from its AC outlet. Makesure that the DC supply is not capable of providing morethan 15 Vdc output at any time. Refer to Figure 2-4 andconnect the DC to the two-pin connector at the rear of theunit.

IWARNING IReversing the polarity may destroy the unit. Note that theconnector is keyed to prevent this.

2.2 POWER SUPPLYDetermine what the power source for the control head willbe. When using the internal supply, check to see that theAC voltage as marked on the unit matches the local

2.3 4 WIRE TO 2 WIRE CONVERSIONThe standard transceiver interface is a 4 wire unbalanced.Converting the system from a 4 wire to a 2 wire 600 ohmline interface requires the following modifIcations.

33 FEET

TW5201

(J12)~======:aa 2:2 ===========l TW100

(J9)

CONNECTOR WIRING TABLE

CABLE ASSEMBLYC991528TW5201 - TW1 00CONTROL CABLE

TO

PIN

6891

FUNCTIONS

GROUNDRX AUDIOTX AUDIOGROUND

PIN

,234

oo~..- en3:3..---+--------If----l t-

FROM

FIGURE 2·1.Control Cable· Remote Control to TW100 Transceiver.

2-1

t---- LENGTH TO BE DETERMINED BY CUSTOMER

RT100/MP I(J2)•...._--- ===============za 22~======= TW5201

(J12)

FROM· TO

PIN

FUNCTIONS

PINH

GROUND 1a.. ARXAUDIO 2:E

.•..TXAUDIO

o~O~ B 3C\! C\!oC\!

1/) .•••.•.. :::2-

~:::2-~ a:

CONNECTOR WIRING TABLE

CABLE ASSEMBLY

C991502TW5201 - RT100/MP'CONTROL CABLE

NOTE: RT1001MP (J2) JUMPER BE1WEEN PINS HAND G.

FIGURE 2-2.Control Cable - Remote Control to RT100/MP Transceiver.

Remove the cover from the control head and the bottomcover of the transceiver. Gain access to the M9 in thetransceiver and remove it It is best to place the M9 on ananti-static bag like the ones used to ship PCB's.

Solder the transformers provided in the 2 wire kit (pN41(028) into both the M9 and the control head PCB (Tlon the M9:rvIP- See Figure 2-S, and 1'2 on the ControlHead - See Figure 2-6).

On the M9, remove the 22 gauge jumpers from "A" to"C", and from "B" to "D". Also remove the jumper intransformer holes "3" and "4". Now jumper together "A"to "X", and "B" to "Y". Replace the M9.

In the control head, remove the wires from 111, pins 3 and4. Reinsert them in J4, pins 6 and 7 respectively. Performthe balancing procedure described in paragraph 2.4.

2.4 BALANCE CHECK, 2 WIRE SYSTEMS ONLYAfter the balanced line has been connected, it may benecessary to adjust the balance on the line at both ends ofthe link. This will only be required, however, if the line is"lossy" (has significant energy losses), or is very muchlonger than the one provided.

2-2

To check the balance, open the cover of the control headand remove the bottom cover of the transceiver to gainaccess to the M9:rvIPmodule. On the M9:rvIPmodule, usea scope or a Sinadder to measure the AC audio voltageacross RSS. RSS is located near the line transformer be­tween two potentiometers, one of which is RS2. See Fig­ure 2-S.

Remove U28 from the M9:rvIPmodule and short pin 12 ofU21 to pin 16 of U21 (+S V). This makes a tone go outfrom the transceiver to the control head. Adjust RS2 for anull in the tone as monitored at RSS. Replace U28 afterpowering down the transceiver. Repower the transceiver.

In the control head, power down and remove U12 (Figure2-6). Short pin 8 of U12 to pin 16 of U12 at its socket.Monitor the non-ground side of the volume control withthe scope or Sinadder. Adjust R29 on the PC board for anull in the transmitted tone. The transceiver should besquelched during this adjustment R29 is a potentiometernear the line transformer. Replace the covers.

2.5 DC KEYING OPTION INSTRUCTIONSRemove the wire from JS pin 8 and reinsert the pin in H2,pin 1. Use the two-pin female connector provided to matewith 112.

:J9

85 4 3

2 1 54321:J7

115V 220V

FIGURE 2-3.Power Transformer Connection.

J12TO TRANSCEIVER

(4 WIRE)TO TRANSCEIVER

(2 WIRE)

r©I~

J912VOC DeFUSE

OFU" '\,

n;3.0A

ACSOURCEAC FUSE (SEE HANDBOOK)

OFU" '\,

:> n;

1.0A (120V)O.5A(240V)

CAUTION: DO NOT CONNECT TO ACAND DC SOURCES AT THE SAME TIME

FIGURE 2-4.Remote Control Rear Panel.

2-3

:00'10'1

:0.0'1I\)

OUR18 U---CJ-;--c::J-

A2'

fDQ3

J.

U2

o~

T'

cjxo..

",

~

J2

'U20

'"

ir

R10S

0108 a"'0 ~ 103 A47~ ~ '" 0 0a: - _ '1 015 040

00'02n 1~ ~:~~05 () 07 0 -9 J7 1ankl:: c:J .• C68 0tl°,... o~ R84 •... L101Q 0Rll,,",O~ - 0 R9 ~ R2-c:J- +- a:O ~() 01 _r--t 00 ~_ 017 A23

~ 1 '1;,0. 0 --.....-,--~ 0 CJ- '0"0, 2 0 --0- /, 0 05o L102 010.,..."'.... Rl

e~s~~~, II U4 II U3 II U'9a:a:~

~ 0o

~OJ

~~~~ ~:;:~~C CC3. "'QCCCC

0+ '" '"

,~d", ~. ¢.¢.~'Q~o' "o,.&~U28~O U2.-R-

C I n' 0 0~ ~ ~~~.. 03. '" ' ,_.- F'7-7 I II CJ9 ~o o,~an')~301 I R:~~ I I o~),1 I I :~ ~'" I I I I I ~~.-c::J-A69,

03'

10

(')031'J0::::s<1>::::s-r00III=.0::::sgIIItoiiJ"3(5- cl\) ~::o

.f:,.<1>m.01\)c,<1>01::::so0'<(')0::::s-...•0

:s:0a.c(i):s:<D:s::0

no3"0o:JCD

:J-boa"o'Q:Je

I\) 0:0&1 iii'm(01\)-,'

llJO>3'()o:J-a:r:CD

llJa.

c..•.I\)

I J7

r---l JII 0cs. RSl ~_

o U6 Jl :;:CD~BDc4B R55 C6~C63 g

R'."~I"::'67B"0IJ3 U'~ RNlnJ5~DORI u.~C6 UR'DD;~;I ••• ' ". 36~,r~~t::';'DALANCELo LJ 0 U U~ R5, 0 lJ <D UDUTV

C55 U1 e 0 C60 6 0 ---r:J CVCLEN VIOl R' D 7 R61 R53 (])D" R27DC17

~D riJn 7 M1CLEVELOUTRI'C'O a U~'D~ R3u"nDora,0U. It, <D "11DR'OB ~90DCIS ;<UDE• C) " " '''. • ,,,m R90N U3

:::nV3 C45 0 R24 n07 C14 C)It: U7 R16 0 t::I Ul1 C16 U13I I 0 r'-'l rlTDNE r---lu8 IR60I I I I - I I I

o I o~ L.....J (I) 0.,. CJ , "' '" CJ 0 "IUS C:J I I e6l LJ ~ MICGAlN 0 R67R30 C41 0R49 0 C) - 0 r-----lJ2 L1 OC12o 0 2732164_ I CS ~ BEADR47 R46 CB I , 3 , 5C30COMPSlDE 735146 REV I 2716-

:00>

:0I\)co

SECTION 3OPERATION

3.1 INTRODUCTIONThe remote control is used in conjunction with thetransceiver. Its operation is similar to that of thetransceiver and most of its control functions are the same.Figure 3-1 shows the front panel of the remote controlwith functions defined by numerical call-outs. These call­outs are referenced in the text by numbers in parenthesesfollowing the section sub-headings.

3.2 FRONT PANEL CONTROLSOperator controls on the transceiver front panel are as fol­lows:

3.2.1 Power On/Off, Audio Gain Control(AUDIO GAIN) (1)

Turns the unit off in the OFF position. (The transceivershould be left on when using the remote control, and viceversa). Adjusts the audio volume in receive mode. FullCCW position is minimum volume and full CW posi­tion is maximum volume.

3.2.2 Remote/Local Control SelectionThe display on the remote indicates "R.C. OFF" when thecontrol is at the transceiver. The display on thetransceiver will indicate "R.C. ON" when the control isfrom the remote. To restore control at either the remoteor the transceiver, press the "F" button.

3.2.3 Speaker On/Off (SPEAKER) (2)A two-position toggle switch that can be used to turn theloudspeaker off.

3.2.4 Squelch On/Off (SQUELCH) (3)This turns the squelch circuits on. The squelch eliminatesbackground noise and is internally set to open on weakvoice signals.

3.2.5 Mode Switches (MODE) (4, 5, and 6)The three mode switches are labeled 4, 5, and 6; they areused to select either USB or LSB operation (4), turn theAM carrier injection on (5), and turn the CW circuitry on(6).

LSB (4), To select LSB operation, turn the USB/LSBswitch to LSB, the AM switch to Off and the CW switchto PTT.

NOTELSB is usually used if there is interference on the othersideband. In many countries (including the USA) thismode is illegal and will not be fitted into the transceiver.

USB (4), Used for most normal SSB operation. Turn theUSB/LSB switch to USB, the AM switch to Off, and theCW switch to PTT.

3-1

AM CSt Compatible AM (AME). This mode is used toprovide a signal that is intelligible to an AM station. It isunlikely to be required for normal communications. Turnthe USB/LSB switch to USB, the AM switch to AM andthe CW switch to PTT.

CW (6). Turn the USB/LSB switch to USB, the AMswitch to Off, and the CW switch to CW to transmitusing the CW key. Turn the switch to "PTT" to receive.

3.2.6 Automatic Antenna Tuner Control (ATU) (7)The ATU switch is used to initiate a tune cycle of anAutomatic Antenna Tuner (ATlOO or RATlOO).Whenever the switch is depressed, the tuner will go into atune cycle; the tuning is automatic and a tone is presentin the loudspeaker during the tune cycle.

3.2.7 External Amp On/Off (AMPL) (8)If an external RF power amplifier is used, its PTT func­tion may be disabled by turning this switch to Off.

3.2.8 Scan Mode Initiate Button (SCAN) (9)Used to control the transceiver scan mode. See paragraph3.9 for operation. The unit scans the same way as thetransceiver. The transceiver scans channels at the rate ofone channel every three seconds.

If the selective call system is fitted, the scan is stoppedby the selective call when a call is received.

3.2.9 Up/Down Tuning Buttons ( i ,J, ) (10, 11)Switch 10 controls the Up tuning and 11 controls theDown tuning. See paragraph 3.8 for operation.

3.2.10 Selective Call Buttons (S.C., CALL)(12,13)Switch 12 controls the entering of the 3-digit selectivecall code and switch 13 controls sending of the selectivecall code. See paragraph 3.10 for operation.

3.2.11 Keypad (14)The keypad is used to program channel frequencies. Seeparagraphs 3.7 and 3.8 for operation.

3.3 FRONT PANEL INDICATORSIndicators on the transceiver front panel include the fol­lowing:

3.3.1 Frequency Display (15)The display shows the selected channel and/or channel fre­quency. A moving decimal point indicates whether areceive or transmit frequency is displayed. For furtheroperation, see paragraphs 3.6 and 3.7.

3.3.2 Loudspeaker (16)The speaker is used during receive and its audio output iscontrolled by the setting of the AUDIO GAIN control

(3.2.1). Turning the SQUELCH switch (3.2.4) on willmute the speaker during conditions of background noiseor extraneous single-tone signals.

3.4 FRONT PANEL CONNECTORAudjo Connector (AUDIO). A 5-pin audio connector isused for either handset or CW operation.

To operate on CW (morse) plug the key into the audiosocket and use either USB or LSB. Put switch in the"CW" position to transmit, "PIT" to receive.

In microphone operation, the internal VOGAD circuit.. automatically adjusts the audio gain to provide full trans­

mitter output. Speak close to the microphone in a clearvoice. Shouting will not provide any increased outputand may reduce intelligibility.

3.5 CHANNEL FREQUENCIESThe preset channel frequencies must be programmed atthe transceiver. To recall any channel frequency, pressthe "F" key as on the transceiver.

3.6 OPERATION - MEMORY CHANNELSELECTION

After specific memory channels have been programmed,re-calling them is a simple matter. The following proce­dure is used.

1. Press the "C" key.2. Press the two-digit channel number

NOTEAll channel numbers have two digits -- 01 to 99. Chan­nel selection is the ~ function available in Mode 3.

3. Press the "F" key to display the receive frequency (themoving decimal pointer on the display will be in the"receive" location).

4. Press the "F" key again to display the transmit fre­quency (the moving decimal pointer on the display willbe in the "transmit" location).

NOTEContinuously pressing the "F" key will cause the displayto alternate between monitoring the receive and transmitfrequency. The display will automatically return to the"receive" frequency after a transmit cycle is ended andthe PIT is released.

3.7 OPERATION - FREE TUNE CHANNELChannel 00 is used for free tuning the transceiver. Bothsimplex and half-duplex frequencies can be programmedinto channel 00. The last entered, frequency is retained inthe transceiver memory.

3-2

3.7.1 PROGRAMMING THE FREE TUNECHANNEL1. Press the "C" key.2. Press the "0" key twice.3. Enter desired channel frequency.4. Press the "F" key. (The selected frequency shouldnow be displayed with the moving decimal pointer at the"receive" location).

3.7.2 PROGRAMMING THE FREE TUNE CHANNELFOR HALF-DUPLEX FREQUENCIES

When one frequency is entered, the transceiver automati­cally assumes that it is a simplex frequency. For half­duplex operating, do the following:

1. Do steps 1 through 4 of section 3.7.1. This programsthe receive frequency.2. Press the "F" key.3. Enter the desired transmit frequency.4. Press the "F" key. The decimal pointer should now bein the "transmit" location.

3.7.3 RECALLING THE FREE TUNE CHANNELSince the last frequency programmed into the free tunechannel is stored in memory, it is an easy matter to re­call this channel.

1. Press the "C" key.2. Press the "0" key twice. The transceiver is now in thefree tune mode and the last entered frequency is displayed.

3.8 FINE TUNING THE TRANSCEIVERThe Up and Down buttons in the front panel per­mit tuning of the transceiver frequency up or down fromthe original programmed frequency. The following proce­dures apply:

1. A single push steps the transceiver 100 Hz. The fre­quency can be changed in 100 Hz steps either up or downby pushing the appropriate button repeatedly (push, thenrelease -- push, release -- etc.).

2. Only the receive frequency can be changed in theabove-mentioned manner. Any change entered is retainedonly until the channel is changed. If the channel ischanged and then changed again back to the original chan­nel, the original frequency is once again displayed; anyfrequency offset previously put in is forgotten.

3. On the free tune channel (CHaO), it is possible tochange the frequency in memory permanently by pressingthe "F" key after any up/down frequency stepping.

3.9 OPERATION - SCAN MODEThe transceiver can scan between 2 and 98 channelswhen in the scan mode. Note that the desired channel fre­quencies must be programmed at the transceiver. Thescan limit must also be set at the transceiver. See theOperation Section of the transceiver technical manual forfurther details.

1. To initiate the scan mode for a desired frequency,press the "SCAN" key. Channels will be scanned at therate of one every three seconds. The channels that will bescanned are defined by the scan limit previously set andretained in memory in the transceiver.

NOTEChannel numbers being scanned will not be displayed bythe Remote Control during the scan sequence.

2. To stop the scan sequence, press the "SCAN" keyagam.

NOTEIt is necessary to stop the scan mode to enter new keypadfunctions.

3.10 OPERATION -- SELECTIVE CALLThe selective calling system is an optional feature.Check that it is fitted to the transceiver before using thisfunction.

Each transceiver is assigned a selective call code (000 to254). This code is internally programmed in the selectivecalling module.

Press the "S.C." key and enter the three digit code for thedesired station. Press the "CALL" button, this will switch

the transmitter on and will then send the selective callcode.

The station called will stop scanning and send back atranspond signal. This respond signal should bemonitored to ensure that the call was received.

Once the call is received, the selective call initiates a 150second scan hold timer, displays "CALL" on the LCD dis­play and sounds the call buzzer.

When a call is received, turn on the loudspeaker andanswer the call. Pressing the "CALL" button automatical­ly updates the scan hold timer for 150 seconds. Alternate­ly press the "SCAN" key to stop the scan. After the callis completed, press any key to cancel the "CALL" dis­play. If the scan mode is in use, press the "SCAN" keyagain to initiate scan.

The loudspeaker may be turned off to eliminate back­ground noise while monitoring the channel in scan mode.

3.11 CW SIDETONEThe Remote Control has been updated to include an audiomuting circuit which suppresses the signalling "chirps"and audio sidetone when in TX mode. To reenable theCW sidetone, remove D9. Plug the CW key into the jackprovided and flip "CW/PTT" switch to "CW" position totransmit, "PIT" to receive.

16

~----------"

---------.--, ,----.----.

___ I __ ----I

POWER © AUDIO GAIN

OND' 0" ".1 V-',

I I: : ;! Cw ( )

, I _, ',_____""

OFF J ©

14

.~iyAUDIO

6

5

B

FIGURE 3-1.TW5201 Remote Control - Front Panel Controls.

3-3

SECTION 4OPERATING NOTES

4.1 ANSWER-BACKWhen any command is given from the control head; Le.,any button is pushed or any switch is toggled, a data burstis sent down to the transceiver and the control head waitsfor an answer indicating that the data were received. Ifthe transceiver, for some reason, does not receive the datacorrectly, it will not send the answer-back. The controlhead will send the data again, and keep trying until it getsan answer.

The data bursts going from the control head to thetransceiver are only weakly audible at the control head,but the answer-back will be audible as a beep comingback from the transceiver. The receiver's audio is mutedduring the answer-back tone.

Controls on the control head will be inactive after thetime the data burst starts and before the answer-back isreceived, so it is good practice to listen for the answer­back before going on to the next command.

The control head is currently programmed to try for theanswer-back 20 times, and then it will give up and indi­cate "Error". This means that in those 20 tries, no answer­backs were correctly received.

All the functions of the remote have to use the databursts, including the PIT (transmit) function. When thePIT switch of the microphone is pressed, you must waitfor the answer-back burst before beginning communica­tions. A high level of background noise at or near theoperating position can cause the outgoing data bursts tobe garbled at the transceiver. It may be necessary toreduce the MIC GAIN in order to stop any such problem.

4.2 MIC GAIN ADJUSTMENTThe MIC GAIN adjustment is inside the control head,near the center of the PCB. Its designator is R6. It isrecommended that the transmission of the unit under testbe monitored while the MIC GAIN is adjusted until thepresence of background noise is at a minimum and doesnot interfere with the signalling. Going too far will causefinal output power to be reduced, as the audio drive maybecome insufficient.

4.3 "WATCHDOG" TIMERThe remote control is equipped with a "watchdog" timerwhich, if the unit is left in transmit from the remote forlonger than five minutes, will cause the transceiver toautomatically revert to receive mode. For transmissionslonger than five minutes, unkey briefly every fourminutes or so.