Found in an American documentation from the 90s, this circuit has a configuration that has been extensively explored in other articles on this site. The FET can be the MPF102 or equivalent.
This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from...
Found in General Electric's 1969 documentation, this circuit uses two Foto Darlingtons to control...
September 2017 - Mouser Electronics is announcing that it already have in its inventories the new...