This is the Coaching materials in Telephony, Cellular and Facsimile Part 1 as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
Telephony, Cellular and Facsimile Coaching Materials Part 1
1. The range of DC current that flows through a telephone is
Ans. 20 mA to 80 mA
2. The typical voltage needed to “ring” a telephone is:
Ans. 90 volts, 20 hertz AC
3. Central offices are connected by:
Ans. trunk lines
4. Call blocking:
Ans. occurs when the central office capacity is exceeded
5. The cable used for local loops is mainly:
Ans. twisted-pair copper wire
6. Loading coils were used to:
Ans. reduce the attenuation of voice signals
7. Signal loss is designed into a telephone system to:
Ans. prevent oscillation
8. The reference noise level for telephony is:
Ans. 1 pW
9. The number of voice channels in a basic FDM group is:
10.Minimum quality circuit available using the PTN.
Ans. basic voice channel *
11.In telephone system FDM, voice is put on a carrier using:
12.In DS-1, bits are “robbed” in order to:
Ans. carry signaling
13.“Bit-stuffing” is more formally called:
14.Compared to ISDN, internet access using ADSL is typically:
Ans. much faster
15. The simplest and most straightforward form of telephone service is called:
Ans. Plain and Old Telephone Service (POTS)
16.The modern Touch-tone telephone is called ______
Ans. 2500-type telephone set
17.The feedback signals that helps prevent the speaker from talking too loudly
18.Aside from the tip and ring used in local loops the third wire when used is called _____
19.In RJ-11, the RJ stands for
Ans. Registered Jack
20.It is a combination of passive components that are used to regulate the amplitude frequency response of the voice signals.
Ans. Equalizer circuit
21.It is a special balanced transformer used to convert a two-wire circuit to a four-wire circuit and vice-versa
Ans. Hybrid network
22.It is the exchange of signaling messages between switching machines.
Ans. Interoffice signaling
23.Category of signaling message that indicates a request for service, going off-hook or ringing in the destination telephone.
24.Signals that provide call status information, such as busy or ringing signals
25.Signals that provide information in the form of announcements such as a number changed to another number, a number no longer in service, and so on
26.Signals that provide the routing information, such as calling and called numbers
27.It is an audible signal comprised of two frequencies: 350 Hz and 440 Hz
Ans. Dial tone
28.It is a method originally used to transfer digits in the telephone to…..the local switch
Ans. Dial pulsing
29.This refers to ability of individuals to retain their existing telephone numbers and the same quality of service when switching to a new location and service provider.
Ans. local number portability *
30.Systems that are simplex wireless communications systems designed to ….subscribers of awaiting messages
31.Early paging system uses what modulation technique
32.Modern paging system uses what modulation technique
Ans. FSK and PSK
33.These are unused sections of cables that are connected in shunt working cables….., such as local loop. They are used for party lines.
Ans. Bridge tap
34.It is a parameter equivalent to TLP except that it is used as a reference for a transmission
Ans. ….. Level Point
35.Weighting technique that assumes a perfect receiver only, therefore its weighting curve corresponds to the frequency response of the ear only
Ans. …ophometric noise weighting
36.It is the difference in circuit gain experienced at a particular frequency with respect to the circuit gain of a reference frequency
Ans. Attenuation distortion
37.It is simply the frequency response of a transmission medium referenced 1004-Hz test tone
Ans. Attenuation distortion, Differential gain or 1004-Hz deviation
38.It is an indirect method of evaluating the phase delay characteristics of a circuit.
Ans. Envelop Delay Distortion
39.The process used to improve a basic telephone channel is called ______.
Ans. Line conditioning
40.Special type of line conditioning that specifies the maximum limit for attenuation distortion and envelope delay distortion
Ans. C-line conditioning
41.The time delay measured in angular units, such as degrees or radians is called _____.
Ans. Phase delay
42.The difference between the absolute delays of all frequencies.
Ans. Phase distortion
43.It is the time required to propagate a change in an AM envelope through a transmission medium
Ans. Envelope delay
44.At the receiver, the phase difference at the different carrier frequencies is called _____.
Ans. Envelope Delay Distortion
45.The reference frequency of a typical voice-band circuit is typically around _____.
Ans. 1800 Hz
46.A special type of line conditioning that sets the minimum requirements for signal-to-noise ratio a nonlinear distortion
Ans. D-type line conditioning
47.It is a communications term that indicates the presence of a signal power comparable to the power of an actual message transmission
48.It is a sudden, random change in the gain of the circuit resulting in a temporary change in the signal level
Ans. Gain hits
49.It is the decrease in gain of more than 12 dB lasting longer than 4 ms and a characteristics of temporary open circuit conditions and are generally caused by deep fades on radio facilities or by switching delays
50.It is the sudden, random changes in the phase of the signal. They are classified as temporary variations in the phase of the signal lasting longer than 4 ms.
Ans. Phase hits
51.It is a form of incidental phase modulation – a continuous uncontrolled variation in the zero crossings of a signal.
Ans. Phase Jitter
52.Phase jitter occurs at what frequency?
Ans. 300 Hz or lower
53.It is used to convert two-wire circuits to four-wire circuits which is similar to hybrid coil found in standard telephone sets.
Ans. Hybrid Circuits
54.The talker hears a returned portion of the signal as an echo, what is the round trip time of delay for an echo to quite annoying?
Ans. 45 msec
55.It eliminates the echo by electrically subtracting it from the original signal rather than disabling the amplifier in the return circuit.
Ans. Echo cancellers
56.A typical echo suppressor suppresses the returned echo by how much?
Ans. 60 dB
57.A type of cross talk which is a direct result of nonlinear amplification in analog communications system
Ans. Nonlinear crosstalk
58.In telephony, functions that identify and connect subscribers to a suitable transmission path
Ans. Switching functions
59.Circuits that are designed and configured for their use only and often referred to as private circuits or dedicated circuits.
Ans. Leased circuits
60.The operator of the instrument
61.It is similar to the local loop except that it used to interconnect two telephone offices.
Ans. Trunk circuits
62.In a telephone channel, _____ is used if the total via net loss of a given trunk circuit exceeds approximately 2.5 dB.
Ans. echo suppressor *
63.It is a central location where subscribers are interconnected, either temporarily or on a permanent basis.
64.The number of dedicated lines used to interconnect 100 parties is
Ans. 4950 lines
65.A switchboard with four digits can accommodate how many telephone numbers
66.The most versatile and popular crossbar switch was ______.
67.The first computer-controlled central office switching system used in PSTN
Ans. No. 1 ESS
68.It is a programmable matrix that allows circuits to be connected to one another.
Ans. Circuit switch
69.A telephone call completed within a single local exchange is called _______.
Ans. Intraoffice call or Intraswitch call
70.The trunk circuits that are terminated in tandem switches are called ______.
Ans. Tandem trunks or Intermediated trunks