# Data Communication and Networking – Multiplexing Demultiplexing technique – FDM / TDM / WDM / MDM MCQs A+ A  A-

This set of Data communication and Networking Multiple Choice Questions and Answers (MCQs) focuses on “Multiplexing Demultiplexing techniques – frequency-division multiplexing (FDM) , Time-division multiplexing (TDM) , Wavelength division multiplexing (WDM) , Mode-division multiplexing (MDM)”.

1
. A multiplexer _______ several transmission streams while a demultiplexer _______ them
• combines; separates
• compresses; decompresses
• encrypts; decrypts
• separates; combines
2
. One _______ can be made of many _______
• channel; paths
• path; channels
• path; links
• channel; links
3
. Which of the following is a digital multiplexing method?
• FDM
• asynchronous TDM
• synchronous TDM
• b and c
4
. Which is not a basic multiplexing method?
• FDM
• TDM
• WDM
• MDM
5
. _______ is an analog multiplexing technique usually involving signals that are not in the visible light frequencies
• FDM
• TDM
• WDM
• MDM
6
. _______ is a digital multiplexing technique usually involving signals that are not in the visible light frequencies
• FDM
• TDM
• WDM
• MDM
7
. _______ is an analog multiplexing technique usually involving signals in the visible light frequencies.
• FDM
• TDM
• WDM
• MDM
8
. In FDM, the bandwidth of the link must be _______ the sum of the bandwidths of the signals to be combined
• equal to
• less than
• greater than
• an order of magnitude greater than
9
. In FDM, if five signals are to be multiplexed, at least _______ carriers, each of a different frequency, must be modulated
• 1
• 5
• 6
• 10
10
. FDM uses _______ to prevent modulated signals from overlapping
• physical hardware devices
• carrier frequencies
• guard bands
• demultiplexers
11
. In FDM, the _______ signals can all have the same frequency range
• modulating
• carrier
• modulated
• b or c
12
. The FDM demultiplexer uses a series of _______ to decompose the multiplexed signal into its constituent signals,
• guard bands
• filters
• repeaters
• amplifiers
13
. WDM is very similar in concept to _______.
• asynchronous TDM
• synchronous TDM
• FDM
• AM or FM
14
. If the sum of the data rates of the sending devices is X, TDM can be applied when the data rate capacity of the transmission medium is _______.
• less than X
• greater than X
• one half X
• two times X
15
. In _______ the multiplexer allocates exactly the same time slot to each device at all times
• synchronous TDM
• asynchronous TDM
• FDM
• WDM
16
. In _______, if a device has no data to send, its time slot remains empty
• synchronous TDM
• asynchronous TDM
• FDM
• WDM
17
. In synchronous TDM, a _______ is a complete cycle of time slots, including one or more slots dedicated to each sending device.
• filter
• carrier
• signal
• frame
18
. What is the efficiency of a system using synchronous TDM if 2 of the 5 devices have nothing to send?
• 20%
• 50%
• 60%
• 100%
19
. In synchronous TDM, if device X has data to send, the data go to _______ in the frame
• the next available slot
• a preassigned slot
• the first slot
• none of the above
20
. In asynchronous TDM, if device X has data to send, the data go to _______ in the frame.
• the next available slot
• a preassigned slot
• the first slot
• none of the above
21
. In synchronous TDM, if device X has no data to send, what happens to its allotted slot?
• The next device in line takes it.
• An error message is sent.
• The bit pattern 01010101 is sent.
• The slot remains empty.
22
. In synchronous TDM, each frame is filled with data from the devices in a fixed order. We call this _______
• interleaving
• synchronization
• switching
• line discipline
23
. _______ allow the demultiplexer to synchronize with the incoming stream
• Slots
• Framing bits
• Demultiplexing bits
• Trailers
24
. In synchronous TDM, if ten devices are each sending data at the rate of 2000 bps, what is the data rate for the line carrying the multiplexed signals?
• 2000 bps
• 20,000 bps
• greater than 20,000 bps
• less than 20,000 bps
25
. What is the major weakness of asynchronous TDM?
• There aren't enough slots in each frame.
• There are too many slots per frame.
• Each slot requires an address.
• All of the above
26
. What is the major weakness of synchronous TDM?
• Some slots may remain empty.
• There aren't enough slots.
• The slots are too small.
• All of the above.
27
. Which type of multiplexing takes data from one high-speed line and breaks it into portions that can be sent across several lower-speed lines simultaneously?
• asynchronous TDM
• synchronous TDM
• FDM
• inverse multiplexing