Dual Tone Siren Circuit Diagram – Build Your Own!

Distinct chime Police sound

Conventional aged ambulance sound

Circuit diagram:

Components:

Circuit operation:

This circuit is designed for recreational purposes, and is appropriate for use in bicycle-powered vehicles, battery-operated cars, and motorcycles, as well as in models and other playthings. When SW1 is positioned as depicted in the circuit diagram, the characteristic dual-tone sound of Police or Fire-department vehicles is produced, due to the oscillation of IC1A and IC1B gates. With SW1 in the alternative position, the aged siren sound, increasing in frequency and then gradually decreasing, is recreated by pressing P1, initiating oscillation in IC1C and IC1D. The loudspeaker, driven by Q1, should be of suitable dimensions and securely enclosed, in order to yield a more realistic and amplified output. The tone and period of the sound oscillations can be adjusted by modifying the values of C1, C2, C5, C6, and/or associated resistors. A power switch is not included; maintain SW1 in the lower position, and the circuit’s power consumption will be minimal.

IC1 - 4093 Quad 2 input Schmitt NAND Gate IC

The 4093 is a versatile integrated circuit, specifically a quad NAND gate IC. It contains four independent NAND gates, each operating as a Schmitt trigger. This means that each gate’s output switches abruptly and reliably, even with noisy inputs. The Schmitt trigger action makes the 4093 particularly useful for creating oscillators and logic circuits that are robust against input noise. It's commonly employed in timer circuits, digital displays, and other applications requiring reliable switching.