Found in an American documentation from the 90s, this circuit uses small low voltage lamps (6 to 12 V0. The circuit can be adapted to use LED indicators.
This circuit was found in a 1990 Electronics Handbook. The transistors can also be the BC548 and...
This circuit is from a 1987 American publication called Electronics Handbook. The circuit can be...
This 1995 documentation circuit detects when an extension on a phone line is active. Adjustment of the...