(ECE Board Exam November 1996)

Term/Answer Definition/QuestionCladding Dielectric material of an optical fiber surrounding the

coreHelical antenna Antenna that is circularly polarized7 ½ A word in telegraphy consists of ______ characters plus a

word space300 Number of voiceband channels in a master group per

CITT standard1 mW Power of standard test toneLORAN Navigational system used primarily for obtaining your

fixed location over large distancesExpander in a companding device

Provides less amplification for low signals

-90 dBm At what power level does a 1 kHz tone cause zero interference (144 weighted)?

Code One character or a sequence of characters forming a part, or the whole of a message with a specific meaning

4/3 K factor under normal atmospheric conditions in a microwave radio data profile calculation

83 dB IBM’s asynchronous data link protocol designationFSK Modulation for telegraphyRS 422 Standard that specifies a balanced interface cable that

will operate bit rates up to 10 Mbps with span distances up to 1200 m

Aperiodic antenna Antenna which is not resonant at particular frequencies and socan be used over a wide band of frequencies

Diffraction Occurs when the microwave beam is at a point of grazing over an obstacle

Humidity, temp, and pressure

Atmospheric condition is controlled by ________.

Length The characteristic impedance of a transmission line does not depend on its _____.

Beat frequency oscillator Generates a 1 kHz note for Morse codePerigee Point on the satellite orbit closest to the earth45 V rms The potential difference between any exposed structured

to ground in any electrical installation should not exceed _______.

Capture area Is directly proportional to the gain of the antennaModems Are required to connect the computer to telephone lines

because the telephone network will pass direct current.Isotropic antenna Standard reference antenna for the directive gainCommunications satellite It is a spacecraft placed in orbit around the earth carrying

on board microwave receiving and transmitting equipment

Pulse duration modulation

Uses pulse that appear as a group and which vary in number according to the loudness of the voice

2 rectifiers in parallel with opposite polarities

A device to be connected across the headset in telephone receivers to reduce the effects of acoustic shock

30 days Judgement on the case against an ECE shall become final and executory after

B8E Independent sideband emission

Space or direct When transmitting and receiving antennas which are in line of sight with each other, the mode of propagation is ____ wave.

Phase shift Passive crossover components cause some frequencies to be delayed with respect to the other frequencies at the crossover point

The clocking is derived from the data in synchronous transmission

The difference between asynchronous and synchronous transmission

F1 Lowest layer of the ionosphere25 pins How many pins are there in a RS232C interface?SSB ½ bandwidth for DSBFC transmissionIndirect Method of generating FM used by broadcastingCommunications code Agreed upon in advance between the sender and

receiver-90 dBm Reference tone level for dBmHertz antenna Undergrounded antennaPulse width modulation Pulse modulation that is analogPurpose of squelch circuit To prevent amplified noise from reaching the

loudspeaker during the absence of an incoming signalTACAN Navigational aid providing hearing and distance

indicationSynchronous In ________ transmission, a unique SYN character is

transmitted at the beginning of each messageInfinite If the terminating impedance is exactly equal to the

characteristic impedance of the transmission line, the return loss is _______

To provide an acceptable replica of the information at the destination

The main purpose of a communications system

Antenna gain The numeric ratio relating the radiated signal strength of an antenna to that of another antenna

Binary communications _________ is better because the components are simpler, less costly, and more reliable

2 In the phase shift method, how many circuits must be balanced?

Determined by the sender and receiver

The correctness and accuracy of the transmitted message content is _______.

Broadside array Consists of a number of dipoles of equal size, equally spaced along a straight line with all dipoles fed in the same phase from the same source

Data switching systems Improve the efficiency of data transferYagi-Uda A type of array antenna which consists of one half-wave

driven dipole, one reflector, and one directorDefinite Power is a ________ amount of energy used in a specific

period of time256 to 2048 Hz The midrange frequency range of sound is from _________Balun To connect a coaxial line to a parallel-wire _____ is best to

use.No In AM, the carrier carries _______ intelligence.Input Characteristic impedance of a transmission line is the

impedance measured at the ______ when its length is infinite

Detector stage Cross modulation on a receiver is eliminated at the _______

The local loop of the telephone system

_____ is a two-wire or four-wire communication circuit between the customer’s premise and the central office

The equatorial region In what region of the world is sporadic-E most prevalent?Quantizing The process of assigning PCM codes to absolute

magnitudesBeamwidth It is a measure of the microwave power radiated from an

antenna as a function of angular direction from the antenna axis

Undergrounding This is not one of the basic electrical protection measures in the Philippine electronics code

Noise weighting curve ________ shows the interfering effect of other frequencies in a voice channel compared with a reference frequency of one kilohertz

Lies in the different definitions of the modulation index

The difference between phase and frequency modulation

Unbalanced When a transmission line uses ground return, it is called a/an ____ line

6 dB over the gain of one antenna

What is the gain of four identically polarized antennas stacked one above the other and fed in phase?

Residual noise level The ratio of the level of the modulated output of a transmitter under conditions of standard test modulation to the level of the demodulated output with no modulation applied both measured with the same bandwidth

Ultraviolet absorption An absorption los caused by valence electrons in the silica material from which fibers are manufactured

Limiters In an fm receiver, which circuit removes amplitude variations?

30 to 53 kHz The frequency spectrum of the stereophonic FM signalTermination ____ means load connected to the output end of a

transmission lineCharacter oriented Asynchronous protocol is __________Ground Transmission lines are either balanced or unbalanced

with respect to the ___0.66 The velocity factor for non-foam dielectric 50 or 75 ohm

flexible coaxial cable such as RG 8, 11, 58, and 590 dB Gain of isotropic antennaLog normal fading Radio fading resulting from obstructionLocal oscillator After the IF stages have been aligned, the next state to

align in FM receiverModem Is a device in data transmission to interface a data

terminal equipment to an analogue transmission lineNo transmitter power is wasted in the carrier

What is the primary advantage of DSBSC in AM?