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.
The figure shows how to implement a filter against interference caused by the switching of a...
The integrated circuit used in this application is the National Semiconductor's LM2907, the...
This simple source uses two 2N3055 transistors that must be equipped with good heat sinks. The...