Question

Marks: Lecture Hall 113 KH is a very large Hall and we need to fix 3 microphone input but only one speaker output so we can at any time select either to listen to the teacher mic or to the male student portable mic or to the female student portable mic The controller is located on the teacher desk. The teacher will start the lecture and have his mic connected to the class speakers, and if any student from the male side have a question the instructor will switch the mic input to the male student portable mic so everybody will hear the question on the class speakers and the same if a female had a question. Then the instructor can switch back his mic and continue the lecture. Notice no two or more mic should work at any given time, but only one should be active at any givern time. Hence if more than one mic is on no output signal will go to the speaker until there is only one input. Call the lecture mic m1, call the boys mic m2 and the girls mic m3 and the speakers s You must design a circuit that will control the above using only ONE KIND of gates either NAND gates, or NOR gates And as an Engineer you must use minimum number of gates as possible. Show all your work with steps and maps with complete gate design and connections Submit your work on a paper

Answer 1

MIL MI 1, 2 Mc3 Sk

We will need 5 NAND gates for making such cicuit

We know truth table of NAND gate ie.

NAND Gate

A	B	OP
0	0	1
0	1	1
1	0	1
1	1	0

Now nand gate is not functional when both inputs are 1. We will keep input for speakers as 1.

Next whenever we need a mic we will give input as 0 to that mic and mic will work.

But if more than one mic is active i.e. given input as zero so outputwill be 1 and NAND gate at the end of circuit will block whole circuit, thus stopping system to work.