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.
To operate with high input voltages using a 3-terminal voltage regulator such as the LM340-15, we...
We found this circuit in the October 1988 Radio Electronics magazine. The circuit is still current...
This audio signal relay was found in an American 1980s documentation. The relay is in accordance...