This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms and excites a load of 16 ohms. The integrated circuit of the time is the PA237.
This is the circuit of a digital clock published in the January 1975 issue of Radio Electronics magazine....
September 2017 - Can be purchased from Mouser Electronics Triacs with 20 A and 30 A currents...
This unusual configuration, due to the component it uses, was found in an old European...