This telegraph monitor was found in an American documentation for radio amateurs from the 1970s. The indicator is a common 1 mA full-scale milliammeter.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
The integrated circuit used in this amplifier is not common today. The circuit is from a...
This circuit turns off a load after an interval of 8 to 80 seconds adjusted on the potentiometer. The...