Quasar ElectronicsAS3031KT - 9V Air Raid Alarm Siren Kithttps://www.quasarelectronics.co.uk/media/ecom/prodsm/3031.jpgA surprising loud siren for such a simple circuit. It uses a voltage controlled oscillator to drive the 1W loudspeaker provided...Electronics > Circuit Components > Printed Circuit Boards > Development Boardsquasar_diy_k313031KTGBP11.95Quasar Electronics LimitednewConditionInStockhttps://www.quasarelectronics.co.uk/Item/3031-9v-air-raid-siren-kit
A surprising loud siren for such a simple circuit. It uses a voltage controlled oscillator to drive the 1W loudspeaker provided. Makes an ideal internal siren for use in fire alarm, burglar alarm and other warning systems.
The alarm output builds in frequency and amplitude to a loud and effective alarm for such a simple circuit. If the On button is repeatedly held and released it sounds somewhat like a high pitch wartime air raid siren or 70's American patrol car. You could experiment with different component values to change the output.