A greenhouse has an electronic system (block diagram is given below ) which automatically switches ON a heater if the air temperature in the greenhouse drops too low . A manual switch is included so that the automatic system can be switched off .
(Hint , The temperature sensor gives a logic -I output when the air temperature is normal and logic 0 when it is too cold )

a. What is meant by 1 and 0 in digital circuit ?
b. Name the logic gate X . Why is it used ?
c. Name the logic gate Y.
d. Construct a truth table of this electronic system by taking A and B as inputs and D as output

Explanation

a - 1 means maximum voltage
0-means minimum voltage
b. NOT gate
To give 1 voltage at Y
c .AND gate
d