CNS-ST 3.2: TELELEPHONY, AND CELLULAR AND FACSiMiLE1.The range of DC current that flows through a telephone is Ans. 20mA to 80mA2.The typical voltage needed to “ring” a telephone is:Ans. 90 volts, 20 hertz AC3.Central offices are connected by:Ans. trunk lines4.Call blocking:Ans. occurs when the central office capacity is exceeded5.The cable used for local loops is mainly:Ans. twisted-pair copper wire6.Loading coils were used to:Ans. reduce the attenuation of voice signals7.Signal loss is designed into a telephone system to:Ans. prevent oscillation8.The reference noise level for telephony is:Ans. 1 pW9.The number of voice channels in a basic FDM group is:Ans. 1210.Minimum quality circuit available using the PTN.Ans. basic voice channel *11.In telephone system FDM, voice is put on a carrier using:Ans. SSB12.In DS-1, bits are “robbed” in order to:Ans. carry signaling13.“Bit-stuffing” is more formally called:Ans. Justification14.Compared to ISDN, internet access using ADSL is typically:Ans. much faster15.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 set17.The feedback signals that helps prevent the speaker from talking too loudlyAns. Sidetone18.Aside from the tip and ring used in local loops the third wire when used is called _____Ans. sleeve19.In RJ-11, the RJ stands forAns. Registered Jack20.It is a combination of passive components that are used to regulate the amplitude frequency response of the voice signals.Ans. Equalizer circuit21.It is a special balanced transformer used to convert a two-wire circuit to a four-wire circuit and vice-versaAns. Hybrid network22.It is the exchange of signaling messages between switching machines.Ans. Interoffice signaling23.Category of signaling message that indicates a request for service, going off-hook or ringing in the destination telephone.Ans. Alerting24.Signals that provide call status information, such as busy or ringing signalsAns. Supervising25.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 onAns. Controlling26.Signals that provide the routing information, such as calling and called numbersAns. Addressing27.It is an audible signal comprised of two frequencies: 350 Hz and 440 Hz28.It is a method originally used to transfer digits in the telephone to…..the local switch29.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 messagesAns. Paging31.Early paging system uses what modulation techniqueAns. FM32.Modern paging system uses what modulation techniqueAns. FSK and PSK33.