This circuit for alternating current loads has a built-in timer. SCR2 is according to the motor current and must be equipped with a heat sink. The circuit is from a 70s GE documentation.
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This amplifier for audio transmission lines was found in a 1961 American publication. The critical...
Old phones with dials can be used in a simple home intercom system, as this circuit from Popular...