This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from 1970s documentation. The components admit equivalents.
This simple circuit with good gain using just one transistor was published in Radio Electronics magazine...
March 2017 - This new component of Vishay has a 16-bit resolution that allows it to be used in a...
Found in documentation from the 1970s, this circuit for resistive loads uses a trigger...