This 4-channel mixer amplifier was found in an American publication from 1947. The circuit uses counterphase output tubes and a transformer power source.
Any power MOSFET that supports the current of the controlled stepper motor can be used on this...
This QST circuit generates 4 frequency signals according to the crystals used. Transistors admit...
This circuit was found in a Popular Electronics of the 1990s. The sensor is a rotating mechanical...