ELEVATE SKILLS!
Q: 1 The number of select inputs required for a 8:1 multiplexer are
2
4
3
1
[ Option C ]
For a multiplexer, the number of select inputs is decided by the relation,
Select Inputs=log2(Number of Data Inputs)
An 8:1 multiplexer has 8 data inputs and only one output, which means we need enough select lines to uniquely choose one of the 8 inputs. Since log2(8) = 3, three select inputs are required.
Q: 2 How many select lines are required for an 8 to 1 multiplexer?
2
3
4
None of the above
[ Option B ]
An 8-to-1 multiplexer selects one input out of 8 possible inputs. To uniquely select any one of these 8 inputs, we need enough select lines to represent all combinations. The number of select lines (n) required is determined using the formula 2n=8. Solving this gives n=3.
Q: 3 In a half-adder circuit, what are the outputs?
Sum and Carry
Difference and Borrow
Sum and Difference
None of the above
[ Option A ]
A half-adder is a basic digital circuit used to add two single-bit binary numbers. It produces two outputs:
Q: 4 To display time in railway stations which digital circuit is used?
Seven-segment decoder
Eight-segment encoder
8 : 3 multiplexer
None of the above
[ Option A ]
Railway stations typically use digital clocks that display time numerically. These clocks use seven-segment displays, where each digit (0–9) is formed by lighting specific segments.
The decoder accepts four BCD inputs A, B, C and D and seven outputs a, b, c, d, e, f and g to display any decimal number from 0 to 9.
To convert BCD (Binary-Coded Decimal) input into signals that light up the correct segments, a seven-segment decoder is used. This decoder determines which segments should glow to represent each digit.
Q: 5 A switching circuit that produces one in a set of input bits as an output based on the control value of control bits is termed as:
Full Adder
Inverter
Multiplexer
Converter
[ Option C ]
A Multiplexer (MUX) is a combinational switching circuit that has multiple input lines, one output line, and a set of control or select lines.
The function of a multiplexer is to select one input from the set of input bits and forward it to the output, depending on the binary value applied to the control lines.
Q: 6 To display time in railway stations which digital circuit is used?
Seven-segment decoder
Eight-segment encoder
8 : 3 multiplexer
1 : 16 Demultiplexer
[ Option A ]
The correct circuit used to display time in railway stations is the seven-segment decoder. This digital circuit takes binary or BCD (Binary Coded Decimal) input and activates specific segments of a seven-segment ((labeled a through g)) display to show digits from 0 to 9.
Seven-segment decoders are commonly used in digital clocks and display boards because they convert numerical data into a human-readable format. Therefore, for displaying time, this is the most appropriate choice.
Q: 7 Which of the following is a combinational logic circuit that has 2n input lines and a single output line?
Multiplexer
Demultiplexer
Encoder
Decoder
[ Option A ]
A Multiplexer (MUX) is a combinational logic circuit that selects one input from 2n input lines and forwards it to a single output line based on n select lines. It effectively channels multiple inputs into a single output line by selecting one input at a time.
| Circuit | No of Inputs | No of Outputs | Description |
|---|---|---|---|
| Multiplexer (MUX) | 2n data inputs and n select lines. | 1 output | Selects one input from 2n inputs based on select lines. |
| Demultiplexer (DEMUX) | 1 data input and n select lines. | 2n outputs | Routes one input line to one of 2n outputs depending on select line values. |
| Encoder | 2n inputs. | n outputs | Converts 2n active input lines into an n-bit binary code on the output lines. |
| Decoder | n inputs. | 2n outputs. | Converts n input bits into 2n outputs where only one output is active based on input code. |
| Half Adder | 2 inputs | 2 outputs (Sum, Carry) | Adds two binary digits producing sum and carry outputs. |
| Full Adder | 3 inputs (including carry in) | 2 outputs (Sum, Carry) | Adds three binary bits including carry-in and produces sum and carry outputs. |
Q: 8 To display time in railway stations which digital circuit is used?
Seven-Segment Decoder
Seven-Segment Encoder
8 to 1 Multiplexer
1 to 16 Demultiplexer
[ Option A ]
Seven-segment decoder एक डिजिटल सर्किट होता है जो बाइनरी या BCD (Binary-Coded Decimal) इनपुट को इस तरह के सिग्नल में बदलता है, जिससे seven-segment display के कुछ खास हिस्से (जिन्हें a–g से नाम दिया जाता है) जलते हैं और वो किसी संख्या (0 से 9) को दिखाते हैं।
✅ इसका इस्तेमाल आमतौर पर डिजिटल घड़ियों, कैलकुलेटर और डिस्प्ले बोर्डों (जैसे रेलवे स्टेशन पर) किया जाता है।
✅ उदाहरण: इनपुट = 0011 (BCD में 3) → डिकोडर a, b, c, d, g सेगमेंट को जलाता है ताकि डिस्प्ले पर 3 दिखाई दे।
Q: 9 The numbers of selection lines for 8 to 1 multiplexer are :
4
1
3
2
[ Option C ]
For a multiplexer, the number of select inputs is decided by the relation,
Select Inputs=log2(Number of Data Inputs)
An 8:1 multiplexer has 8 data inputs and only one output, which means we need enough select lines to uniquely choose one of the 8 inputs. Since log2(8) = 3, three select inputs are required.
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