Found in a 1968 Motorola documentation, this circuit operates at 1 kHz and can deliver 20 V from 12 V. Transistors support modern equivalents.
This circuit was found in a Popular Electronics of the 90s. It operates a third brake light that...
This sonic switch, sound relay or simply vox uses a medium impedance speaker as a microphone. The...
Using neon lamps, this circuit from a 1969 publication provides 17 V of maximum voltage or else...