Found in a Popular Electronics from the 90's, this circuit detects the approach of objects by the reflection of the radiation emitted by the LED. The relay is a 12 V sensitive type.
Using the 2N2646 this circuit was found in a Radio Electronics magazine from July 1968. The...
The purpose of this circuit found in a 1990s Popular Electronics is to increase the current...
Found a documentation for PC from 1992, this circuit is indicated for the English power grid of...