# Digital Circuits Questions and Answers – Multiplexers (Data Selectors)

This set of Digital Electronics/Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Multiplexers (Data Selectors)

1. One multiplexer can take the place of ___________
a) Several SSI logic gates
b) Combinational logic circuits
c) Several Ex-NOR gates
d) Several SSI logic gates or combinational logic circuits

Explanation: Depending on the active select lines, a multiplexer (or MUX) picks one of several analog and digital input signals and feeds the selected input into a single line. Because a multiplexer can perform a wide range of operational functions. A combinational circuit, on the other hand, is made up of multiple logic gates, making the circuit more complex.

2. A digital multiplexer is a combinational circuit that selects ___________
a) One digital information from several sources and transmits the selected one
b) Many digital information and convert them into one
c) Many decimal inputs and transmits the selected information
d) Many decimal outputs and accepts the selected information

Explanation: A digital multiplexer is a circuit that picks one piece of digital information from numerous sources and transmits it on a single output line, based on the status of the select lines. It’s also known as a data selector because of this.

3. In a multiplexer, the selection of a particular input line is controlled by ___________
a) Data controller
b) Selected lines
c) Logic gates
d) Both data controller and selected lines

Explanation: A set of selected lines in a multiplexer controls the selection of a particular input line, which aids in the selection of a particular input from various sources.

4. If the number of n selected input lines is equal to 2^m then it requires _____ select lines.
a) 2
b) m
c) n
d) 2n

Explanation: When the number of n selected input lines equals 2m, m select lines are required to select one of the m select lines.

5. How many select lines would be required for an 8-line-to-1-line multiplexer?
a) 2
b) 4
c) 8
d) 3

Explanation: For MUX, there are 2n input lines, n control lines, and 1 output line available. In this case, 8 input lines equal 23 inputs. As a result, three control lines are feasible. The input is picked and sent to the output based on the status of the select lines.

6. A basic multiplexer principle can be demonstrated through the use of a ___________
a) Single-pole relay
b) DPDT switch
c) Rotary switch
d) Linear stepper

Explanation: A rotary switch can be used to show a simple multiplexer principle. Because it behaves similarly to a multiplexer. There are approximately ten digits, each of which is selected and supplied to the output one at a time.

7. How many NOT gates are required for the construction of a 4-to-1 multiplexer?
a) 3
b) 4
c) 2
d) 5

Explanation: There are two NOT gates required for the construction of 4-to-1 multiplexer. x0, x1, x2 and x3 are the inputs and C1 and C0 are the select lines and M is the output.
The diagram of a 4-to-1 multiplexer is shown below:

8. In the given 4-to-1 multiplexer, if c1 = 0 and c0 = 1 then the output M is ___________

a) X0
b) X1
c) X2
d) X3

Explanation: The output will be X1, because c1 = 0 and c0 = 1 results into 1 which further results as X1. And rest of the AND gates gives output as 0.

9. The enable input is also known as ___________
a) Select input
b) Decoded input
c) Strobe
d) Sink

Explanation: The enable input, often known as strobe, is used to build a multiplexer with a larger number of inputs by cascading two or more multiplexer ICs. The multiplexer is turned on when you enable input.

10. What is a multiplexer?
a) It is a type of decoder which decodes several inputs and gives one output
b) A multiplexer is a device which converts many signals into one
c) It takes one input and results into many output
d) It is a type of encoder which decodes several inputs and gives one output

Explanation: Depending on the active select lines, a multiplexer (or MUX) picks one of numerous analogue or digital input signals and feeds the selected input into a single line.

11. Which combinational circuit is renowned for selecting a single input from multiple inputs & directing the binary information to output line?
a) Data Selector
b) Data distributor
c) Both data selector and data distributor
d) DeMultiplexer

Explanation: Multiplexer is also known as Data Selector. Depending on the active select lines, a multiplexer (or MUX) picks one of numerous analogue or digital input signals and feeds the selected input into a single line.

12. It is possible for an enable or strobe input to undergo an expansion of two or more MUX ICs to the digital multiplexer with the proficiency of large number of ___________
a) Inputs
b) Outputs
c) Selection lines
d) Enable lines

Explanation: An enable or strobe input can be expanded using two or more MUX ICs to create a digital multiplexer capable of handling a large number of inputs.

13. Which is the major functioning responsibility of the multiplexing combinational circuit?
a) Decoding the binary information
b) Generation of all minterms in an output function with OR-gate
c) Generation of selected path between multiple sources and a single destination
d) Encoding of binary information

Explanation: Because it makes the circuit too flexible, the multiplexing combinational circuit’s main role is to generate a selected path between several inputs and a single destination. Depending on the active select lines, a multiplexer (or MUX) picks one of numerous analogue or digital input signals and feeds the selected input into a single line.

14. What is the function of an enable input on a multiplexer chip?
a) To apply Vcc
b) To connect ground
c) To active the entire chip
d) To active one half of the chip

Explanation: The enable input is used to activate the chip; when it is high, the chip is active (ACTIVE); when it is low, the chip is inactive (MEMORY). Enable, on the other hand, can be Active-High or Active-Low, indicating that it is active when connected to VCC or GND, respectively.

A multiplexer (or mux; often written multiplexor), also known as a data selector, is a device that selects one of numerous analogue or digital input signals and sends it to a single output line. A separate set of digital inputs known as select lines controls the selection. Displaystyle nn choose lines are used to pick the input line to send to the output in a multiplexer with displaystyle 2n2n inputs.
Instead of having one device per input signal, a multiplexer allows several input signals to share one device or resource, such as an analog-to-digital converter or a communications transmission medium.