Found in American documentation from the 1980s, this circuit has a diode feedback. At the exit we have an indicator LED. The LM3900 is a transconductance operational amplifier.
We found this source with the CI 723, common at the time, in a 1989 paper. Power transistors must be...
Found in an American 80's documentation, this circuit can use common FETs like the BF245 and cover...
This simple passage alarm is powered by the power grid using an LDR as a sensor. The circuit is...