This circuit makes use of an optical coupler to isolate the telephone line. The circuit is from 1970s documentation. The components admit equivalents.
This circuit is from a 1967 publication. The Triac can be any of the TIC series. The series...
This circuit was obtained in old documentation, but it is valid for modern triacs that must be...
This circuit charges a battery to power a flashlight at night. The circuit is from an English...