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 with only two transistors is from an 80's EDN. It can be implemented with two current...
This circuit was originally designed to measure the gain of two-door RF MOSFETs as indicated by...
This circuit was obtained from an 80's linear integrated circuits manual. Modern operational...