We found this circuit in a 1968 General Electric publication. The circuit uses an SCR of the time, but any modern equivalent can be used. The relay must have contacts that support the horn current.
This circuit causes an instrument needle to oscillate to signal an event. The circuit is powered by...
The resistors on this circuit from an American publication from the 70s are 220 ohms. The circuit...
This circuit can be used as a buzzer from 3 different locations, allowing you to identify where it went...