Found in a 1990s American technical brochure, this circuit is intended for alarms that use as photodiode sensors. The circuit has a frequency response of up to 20 kHz. The gain is 40 dB.
Found in a 1968 US publication, this circuit can operate on any power grid. The thickness of the wire...
In the figure we have a simple timer with the 555 feeding a relay directly. The circuit is from...
A simple electroscope can be made only with a 741, without the need for field effect transistors or other...