A simple electronic buzzer can be made using electronic diagram below. This circuit produces an "big bang" sound ordered by an piezoelectric element so as to vary both loudness and pause between "big" and "bang." The signal produced by piezoelectric element is firstly amplified by operational amplifier A1. Since the elements have a high piezoelectric ohmic resistance, is the operational amplifier A1 better be embedded in the ring button. Output with low ohmic resistance of A1 can be connected to the rest of the assembly together with power wires in a four-wire cable.
This electronic siren is built with LM389 chip. With transistors T1 and T2 was built astabil multivibrator whose frequency can be adjusted with potentiometer P1 between 1 and 7 Hz. Multivibrator produces a square wave that is available to the collector of T2 (pin 11 of IC1) and the control transistor T3. This transistor is connected to the emitter or muting the amplifier input. Now muting input is connected on the frequency rate of multivibrator with supply voltage and thus attenuates at the same rate, the output signal of the amplifier.