This is one of the many modulated siren versions that can be found on our website. We found it in a Hands On Electronics from the 90s.
This circuit is temperature stabilized. Modern equivalent transistors can be used, and the power...
This circuit uses an optocoupler to obtain a solid state relay whose power depends on the Triac...
This power step for relay activation was found in the 1964 RCA transistors manual. The circuit is of the...