This is a Simple Warble Tone Alarm Circuit Diagram. The circuit generates a warble-tone alarm signal that simulates the sound of a British police siren. IC1 is wired as an alarm generator and IC2 is wired as a 1 Hz a stable multivibrator.
Simple Warble Tone Alarm Circuit Diagram
The output of IC2 is used to frequency modulate IC1 via R5.The action is such that the output frequency of IC1 alternates symmetrically between 500 Hz and 440 Hz, taking one sound to complete each alternating cycle.