This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from 1970s documentation. The components admit equivalents.
This precision circuit was found in ancient American documentation. The most critical component is the...
This circuit drives a load with a delay given by the RC timing components. The circuit is from...
This project is from a 1982 documentation, based on an astable multivibrator with two transistors. The...