# Computer Networks Questions & Answers – Multiplexing

This set of Computer Networks Multiple Choice Questions & Answers (MCQs) focuses on “Multiplexing”.

1. The sharing of a medium and its link by two or more devices is called _________
a) Fully duplexing
b) Multiplexing
c) Micropleixng
d) Duplexing

Explanation: Multiplexing is a method using which one can send multiples signals through a shared medium at the same time. This helps in using less resources and thus saving the cost of sending messages.

2. Multiplexing is used in _______
a) Packet switching
b) Circuit switching
c) Data switching
d) Packet & Circuit switching

Explanation: Circuit switching is a switching method by which one can obtain a physical path between end points. Circuit switching method is also called a connection oriented network. Two nodes must be physically and logically connected to each other to create a circuit switching network.

3. Which multiplexing technique used to transmit digital signals?
a) FDM
b) TDM
c) WDM
d) FDM & WDM

Explanation: TDM abbreviation for Time Division Multiplexing is a method used for digital signals. Whereas FDM and WDM abbreviation for Frequency Division Multiplexing, and Wavelength Division Multiplexing, are used for analog signals. TDM is used in applications like ISDN (Integrated Services Digital Network) and PSTN (Public Switched Telephone Network).

4. If there are n signal sources of same data rate, then the TDM link has _______ slots.
a) n
b) n/2
c) n*2
d) 2n

Explanation: In TDM, the total unit of time is divided equally among all the signal sources and each and every source has access to the complete channel bandwidth during its allotted time slot. When the time slot of the source is not active, it remains idle and waits for its slot to begin.

5. If link transmits 4000frames per second, and each slot has 8 bits, the transmission rate of circuit this TDM is _________
a) 32kbps
b) 500bps
c) 500kbps
d) 32bps

Explanation: Transmission rate= frame rate * number of bits in a slot.
Given: Frame rate = 4000/sec and number of bits in slot = 8
Thus, Transmission rate = (4000 * 8) bps
= 32000bps
= 32kbps

6. The state when dedicated signals are idle are called __________
a) Death period
b) Poison period
c) Silent period
d) Stop period

Explanation: There are instances when connection between two endpoints has been established, but no communication or transfer of messages occurs. This period of time is called silent period. The silent period ends when either of the two endpoints starts the communication.

7. Multiplexing provides _________
a) Efficiency
b) Privacy
c) Anti jamming
d) Both Efficiency & Privacy

Explanation: Multiplexing helps us to transfer our messages over a shared channel. This brings up the issue of privacy and efficiency. Fortunately, Multiplexing has high efficiency and high privacy when implemented because in the implementation, the transport layer of the OSI network model handles the function of multiplexing through interfaces called ports which provide the required efficiency and privacy.

8. In TDM, the transmission rate of a multiplexed path is always _______ the sum of the transmission rates of the signal sources.
a) Greater than
b) Lesser than
c) Equal to
d) Equal to or greater than

Explanation: In TDM the transmission rate provided by the path that is multiplexed will always be greater than the sum of transmission rates of the single sources. This happens because the transmission rate is provided to each source only for a small period of time.

9. In TDM, slots are further divided into _________
a) Seconds
b) Frames
c) Packets
d) Bits

Explanation: TDM is the abbreviation for Time division multiplexing. It is technique for combining several low rate channels to a single high rate channel. For a certain time slot, the several channels could use the maximum bandwidth. Each channel is inactive for a period of time too. Some other multiplexing techniques are Frequency division multiplexing and Phase division multiplexing.

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