1. Examples of digital communication are
a) ISDN
b) Modems
c) Classical telephony
d) All of the mentioned
Explanation: Some of the examples of digital communication systems are classical telephony, ISDN, Modems, LANs, PCM TDM etc.
2. Which system uses digital transmission?
a) ISDN
b) LANs
c) ISDN & LANs
d) None of the mentioned
Explanation: Though the signal type is analog or digital, the transmission takes place in the digital domain in ISDN and LANs.
3. The interval of frequencies outside which the spectrum is zero is called as ________
a) null to null bandwidth
b) normalized bandwidth
c) absolute bandwidth
d) none of the mentioned
Explanation: The measure of frequencies outside which spectrum is zero is called as absolute bandwidth. It is usually infinite.
4. The attenuation level in bounded power spectral density is
a) 35
b) 50
c) 35 & 50
d) none of the mentioned
Explanation: Bounded power spectral density is the bandwidth outside which the spectrum must have fallen to a stated level below that found at the band center.
5. Synchronization available in digital communication are
a) Symbol synchronization
b) Frame synchronization
c) Carrier synchronization
d) All of the mentioned
Explanation: The synchronization techniques available in digital communication are symbol synchronization, frame synchronization and carrier synchronization.
6. Digital system includes
a) Difficult data multiplexing
b) Better encryption algorithm
c) All of the mentioned
d) None of the mentioned
Explanation: Digital system has an advantage of better encryption algorithm, easier data multiplexing and more reliability.
7. Analog to digital conversion includes
a) Sampling
b) Quantization
c) Sampling & Quantization
d) None of the mentioned
Explanation: Analog to digital conversion is a two step process which includes sampling and quantization.
8. What are the main features of a receiver?
a) Synchronization
b) Multiple parallel receiver chain
c) Synchronization & Multiple parallel receiver chain
d) None of the mentioned
Explanation: The main features of a receiver which increases its complexity are synchronization of carrier, phase, and timing and multiple parallel receiver chain.
9. Wired channels are
a) Lossless
b) Lossy
c) Lossy & Lossless
d) None of the mentioned
Explanation: Wired channels are lossy channels.
10. What conditions must be fulfilled in a good digital communication system?
a) Low transmit power
b) High data rate
c) High fidelity
d) All of the mentioned
Explanation: Some of the conditions which must be satisfied in a digital communication system are high data rate, high fidelity, low bandwidth, low transmit power and low transmitter and receiver complexity.