Instant communication relay picks-up simultaneously to the input signal and then at each point of the sinusoidal output voltage curve and dropout at zero-current. It can particularly be used where high commutation frequency is required together with the possibility of commutating, by means of limited control voltage, high currents with 4KV insulation between input-output.

Instantaneous Relay is a solenoid with a vertically movable iron core or plunger. This relay operates and resets with no intentional time delay. Instantaneous relay is energized and timing starts as soon as power is switched on.