After a power outage, it is prohibited to reconnect the circuit when a call comes in b

It is forbidden to reconnect the circuit
when a call comes after a power outage. This can avoid accidents caused by forgetting to turn off the electrical appliances and power grid in use when the power comes back again . It can be easily implemented using relays or contactors, as shown in Figure 13-77 (a), but the relay coil
consumes power, and when the load power is large, contactor control is required, which is bulky and noisy . If
a bidirectional thyristor is used as a contactless switch , the problem can be solved.