Q$24)$ Consider a simple telephone network consisting of two end offices and one intermediate

switch with a $1-MHz$ full$-$duplex trunk berween cach end office and the internediate switch.

Assume a $4-kHz$ channel for each voice call. The average telephone is used to make four calls per

$8-$hour workday, with a mean call duration of six minutes. Ten pereent of the calls are long$-$

distance. What is the maximum number of telephones an end office can suppor?

a$)50,000$ tclephemes

b$)100,000$ telephones

c$)20,000$ telophones

d$)25,000$ telephones

c$)10,000$ telephones

fo No answer is correct

Q$25)$ Assume that there is a virtual circuit from station $x$ through nodes a and $b$ to station $Y.$ The

message to be sent comprises $40$ octets, and each packet contains $3$ octets of control information.

which is placed at the beginning of each packet and is referred to as a beader. Suppose that we

break the message up info eight packets. The total transmission time will be:

a$)88$ octet$-$times

b$)72$ octel$-$imes

c$)80$ octet$-$limes

$-1)64$ octe$-$times

c$)96$ octet$-$limes

I$)$ No answer is correc:

$)9..mm$

Q$22)$ Twenty$-$four voice signals are to be multiplex ed and transmitted over twisted pair. Assuming

a bandwidth efficiency of $1$ bps $H$ lz$,$ what is the bandwidth required for TDM using PCM$!$

a$)1\mathrm{.}190MHz$

b$)1\mathrm{.}536MHz$

c$)74\mathrm{.}4kHz$

d$)24kHz$

c$)96kHz$

f$)$ No answer is comect

Q$14)$ A telephone line is known to have a loss of $20dB.$ The input signal power is measured as

$0\mathrm{.}45W,$ and the output noise level is measured as $5W.$ Using this information, calculate the

output signal$-$to$-$noise ratio.

Q$15)$ A communication system uses multiple FSK $($MFSK$)$ for the transmission of the signals

where $f_c=250kHz,f_d=25kHz,$ and $L=3$ bits. Therefore, the modulator requires a

bandwidth of:

a$)200kHz$

b$)100kHz$

c$)325kHz$

d$)375kHz$

c$)400kHz$

$(1)$ No answer is correct