This sonic relay or vox was found in a Popular Electronics from the 90's. The power MOSFET can be of any type determining the controlled load.
This circuit was obtained in a Motorola manual, but it applies to almost any operational...
Found in a 1970 EEE this circuit emulates a zener diode whose voltage can be set to R2. Power...
This circuit different from the timer was found in an English publication from 1978. The circuit uses...