@▷ Two-Tone Siren Circuit Schematic Using One IC | Diagram for Schematic

Two-Tone Siren Circuit Schematic Using One IC

Two-Tone Siren Circuit Schematic Using One IC

Circuit Description

This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or Fire-brigade cars is generated, by the oscillation of IC1A and IC1B gates. With SW1 set to the other position, the old siren sound increasing in frequency and then slowly decreasing is reproduced, by pushing on P1 that starts oscillation in IC1C and IC1D.

The loudspeaker, driven by Q1, should be of reasonable dimensions and well encased, in order to obtain a more realistic and louder output. Tone and period of the sound oscillations can be varied by changing the values of C1, C2, C5, C6 and/or associated resistors. No power switch is required: leave SW1 in the low position (old-type siren) and the circuit consumption will be negligible.

Circuit diagram:

Two-Tone Siren Circuit Schematic Using One IC-Circuit diagram


  • R1 = 470K - 1/4W Resistors
  • R2 = 680K - 1/4W Resistor
  • R3 = 470K - 1/4W Resistors
  • R4 = 82K - 1/4W Resistor
  • R5 = 330K - 1/4W Resistor
  • R6 = 10K - 1/4W Resistor
  • R7 = 33K - 1/4W Resistor
  • R8 = 3.3M - 1/4W Resistor
  • C1 = 10µF - 25V Electrolytic Capacitors
  • C2 = 10nF - 63V Polyester Capacitors
  • C3 = 100nF - 63V Polyester Capacitor
  • C4 = 100µF - 25V Electrolytic Capacitor
  • C5 = 10µF - 25V Electrolytic Capacitors
  • C6 = 10nF - 63V Polyester Capacitors
  • D1 = 1N4148 - 75V 150mA Diodes
  • D2 = 1N4148 - 75V 150mA Diodes
  • D3 = 1N4148 - 75V 150mA Diodes
  • Q1 = BC337 - 45V 800mA NPN Transistor
  • P1 = SPST Pushbutton
  • B1 = 6V Battery (4 AA 1.5V Cells in series)
  • IC1 = 4093 - Quad 2 input Schmitt NAND Gate IC
  • SW1 = DPDT Switch
  • SPKR= 8 Ohm Loudspeaker
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