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.
Found in Elektor Electronics from the 90s, this circuit produces the tone of 1 750 Hz for calling VHF...
This circuit was found in a European documentation from 1964. The circuit makes use of components of...
This circuit is from 1983 documentation. The author shows us an experimental circuit of a siren...