Circuits with the aim of performing a memory action. This is possible in three ways:
- Memory forms with a lock and dominant activation, i.e. they turn on when both signals for on and off are pending;
- memory, in which the shut-down is dominant when both signals are pending, i.e. the Off transmitter interrupts the entire circuit. They are chosen to increase safety;
- Memory that is dominant for the first signal, as is the case with impulse valves. They are used, for example if you want to ensure that after power is lost and returns, the control is in the starting position.