We found this circuit in 1967 General Electric documentation. SCRs can be replaced by current equivalents. The circuit is for 110V power grid.
This circuit was found in a 1970s General Electric documentation. Transistors are uncommon today....
Found in Ferranti's 1969 documentation, this circuit can be mounted with a modern equivalent...
This circuit beeps when the sensor is triggered by the opening of the freezer door or other...