The SC-64 substation annunciator is freely programmable device, which indicates occurrence of substation signal by optical indicators. Received signals can be grouped and individually assigned to optical indicators, relay outputs or quitting inputs. Inputs are energized by control voltage. Input pick-up can be programmable delayed with delay time up to 25 seconds. Disturbance optical signalling is realized by blinking light of frequency 2 Hz. Quitting of the optical signals is possible only after quitting of acoustic signals. Sustained signal of disturbance, after blinking mode quitting, is further signalled by continuous light. If quitted disturbance is vanished, the optical indicator blanks. Every acoustic channel (TRIP, Failure, Al1, Al2) can be picked-up by any of disturbance input. Every disturbance input is supported by interlock circuit against excess of data coming from damaged channel.