The protective device which will not open the circuit even after 4 hours, when the current is 1.5 times the excess of the rated current will be

15) Which type device, switches are classified ?

16) Different types of switches are being used in lighting circuits. Which switch is used for stair case wiring ?

17) How many two way switches are required for the stair case wiring ?

18) The specification surface type tumbler switch, one way is