We found this circuit in a 1969 General Electric documentation. The circuit uses transistors of the time and the diodes in the dotted board must be mounted on the output transistor heatsinks.
This circuit uses a contactor having been found in a 1987 publication. More modern equivalent...
This circuit was found in a 1977 Radio Shack documentation. Its purpose is to generate 1 Hz...
This circuit was found in a 1980s documentation. It decodes by identifying a certain frequency tone...