This circuit was found in a Radio Electronics magazine from June 1962. The circuit is for cars of the time with platinum ignition. The indication is made on an analog instrument.
This circuit for controlling high power in the AC network was found in a Motorola documentation from 1968....
This amplifier is specifically designed for portable radio and recorders with a 4 ohms load....
This circuit was found in a 1973 Radio Elettronica magazine. The Italian magazine no longer...