Q$1-$Consider a simple telephone network consisting of two end offices and one intermediate switch with a $1-$ full$-$duplex trunk berween cach end office and the internediate switch. Assume a $4-$ 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 percent of the calls are long$-$distance. What is the maximum number of telephones an end office can suppor?

a$)50,000$ telephones

b$)100,000$ telephones

c$)20,000$ telophones

d$)25,000$ telephones

e$)10,000$ telephones

f$)$ No answer is correct

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Q$2-$ Hosts A and B are exchanging frames using stop$-$and$-$wait flow control $.$ The propagation time of the link between the two hosts is $12$ ms $,$ and the transmission time of a frame is $2$ ms $.$ if host A stars sending a frame to host B at time $0,$find the time at which host. A receives the first bit of the ACK message from host B $($ The ACK frame has the same size as the data frames $)$

a$)14$ msec

b$)28$ msec

c$)12$ msec

d$)16$ msec

e$)26$ msec

f$)$ No answer is correct

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Q$3-$ in a QAM scheme $,8-$level ASK is used to encode the I components $,$ and to encode the Q components $.$ If the signaling rate is $20$ kbaud $.$ The data rate is :

a$)20$ kbps

b$)160$ kbps

c$)120$ kbps

d$)100$ kbps

e$)64$ kbps

f$)$ No answer is correct

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Q$4-$ X voice signals are to be multiplexed and transmitted per twisted per $.$ Assuming each sample is represented by $8$ bits and bandwidth efficiency of $4$ kbps$/$ HZ what is the bandwidth required for TDM using PCM $?$

a$)8$X KHZ

b$)16$X KHZ

c$)32$X KHZ

d$)64$X KHZ

e$)128$X KHZ

f$)$ No answer is correct

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Q$5-$ when the DS$-$I format is used to provide voice transmission service for X of every six frame $,8-$bits PCM samples are used

a$)$ X$=1$

b$)$ X$=2$

c$)$ X$=3$

d$)$ X$=4$

e$)$ X$=5$

f$)$ No answer is correct

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Q$6-$ in a CRC scheme the message is $11001,$ the pattern used for encoding is $1101,$the frame check sequence $($ FCS$)$ is :

a$)000$

b$)010$

c$)001$

d$)011$

e$)100$

f$)$ No answer is correct