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 an Italian publication from 1988 but can still be easily assembled....
We found this circuit in a Japanese publication in 1967. The circuit consists of a 15 W audio...
This charger circuit provides an initial voltage of 2.5 V and when the current reaches 180 mA the...