This circuit activates a recorder from the signal obtained from a telephone line in the service. It is used to make automatic call recordings.
Hughes suggests this circuit in a 1968 documentation. The circuit uses old transistors that can be...
Using a single Darlington phototransistor, this circuit drives a highly sensitive relay, for...
This source whose voltage depends only on the zener diode used, can supply currents up to about 3 A....