Why is the alarm lamp blinking instead of constantly on?

In general, there is an alarm, after turning it on, when activated, a light should light up along with the sound, but it blinks, but does not constantly light, blinks at the beat of a click of a call (such a USSR). I checked the base of the bulb and the switch, there is no damage in the twists, I think there is some problem in the call itself, I don’t understand what to think, since it’s not experienced yet?