This circuit is for traditional old-style telephone lines found in an American 1980s documentation. Components are common and the optical coupler can be replaced with an equivalent.
This photometer is based on a Wheatstone bridge that must be balanced by the linear potentiometer P1. The...
Found in a 1980s American documentation, this circuit operates with 5 V signals requiring 55...
This circuit is from the time when cars used contact breakers. This 80's version measures the dwell...