1. Devices used in digital exchange for switching are:
(A) Diodes
(B) Transistors
(C) Logic gates
(D) SCRs
2. Switching is controlled in digital exchange with:
(A) Computer
(B) Thyristor
(C) Diode
(D) Relay
3. Digital exchange switching is used:
(A) All of these
(B) Space switching
(C) Space-time switching
(D) Time switching
4. In digital exchange, the subscriber lines are connected to:
(A) LTG
(B) DLU
(C) Switching network
(D) Computer
5. A process in which a number of signals are transmitted on one channel is called:
(A) Modulation
(B) Demodulation
(C) Amplification
(D) Multiplexing
6. Frequency division multiplexing is used in:
(A) Digital transmission
(B) Amplification
(C) Analog transmission
(D) Heterodyning
7. Frequency of subgroup in FDM band is:
(A) 24 to 48 KHz
(B) 12 to 24 KHz
(C) 12 to 16 KHz
(D) 12 to 20 KHz
8. In pulse code modulation, code is used:
(A) Morse code
(B) Binary code
(C) Cable code
(D) 7.5 unit code
9. PCM system used in Pakistan is:
(A) PCM 20
(B) PCM 24
(C) PCM 35
(D) PCM 30
10. There are channels used in Pakistan in PCM system:
(A) 20
(B) 30
(C) 24
(D) 35
11. Frequency band of telephone channel is:
(A) 16 KHz
(B) ___
(C) 8 KHz
(D) 4 KHz
12. Sampling frequency in PCM is:
(A) 80 Hz
(B) 8000 Hz
(C) 800 Hz
(D) 8 MHz
13. Sampling frequency is ______ than the signal:
(A) Twice
(B) 3 times
(C) 4 times
(D) 5 times
14. A PCM word consists of:
(A) 4 bits
(B) 8 bits
(C) 6 bits
(D) 12 bits
15. One of the following is a digital signal:
(A) AM
(B) PCM
(C) PAM
(D) FM
16. There are number of time slots in primary digital carrier:
(A) 912
(B) 40
(C) 128
(D) 32
17. The bit rate of primary digital carrier is:
(A) 64 Kb/sec
(B) 4 Mb/sec
(C) 2 Mb/sec
(D) 8 Mb/sec
18. Fax works like a:
(A) Telephone
(B) Teleprinter
(C) Photostat Machine
(D) None of these
19. Fax documents are sent by:
(A) Direct
(B) By telephone
(C) By camera
(D) By electronic signaling
20. MODEM converts:
(A) Audio tones into binary code
(B) Both a & b
(C) Binary codes into audio tones
(D) None of these
21. In data communication, data on telephone line is in form of:
(A) Binary code
(B) Binary code & Audio tones
(C) Audio tones
(D) Telegraphy codes