This circuit was found in documentation from the 1980s. The circuit uses several components of the time, which are uncommon today. We must not supply it with a transformerless power supply.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit transmits the audio signals from a telephone line to an FM receiver placed nearby. The...
This circuit is from an old manual of operational amplifiers. The setting can be adapted to work...