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.
This simple circuit for motors that depends on the MOSFET used was found in the January 1998...
This transistorized shield also functions as a logic gate. The power supply can be in the range of 4.5...
Found in a 90s Popular Electronics, this Hartley oscillator uses an output transformer of the type...