Found in a 1924 publication, this 2-valve receiver has a speaker output. Power comes from several batteries. Information about the coils is given.
Any power MOSFET that supports the current of the controlled stepper motor can be used on this...
This water level control circuit was found in a 1980s documentation. The circuit uses a capacity...
Found in a Popular Electronics from the 90s, this digital recording circuit uses an unusual...