This 4-voltage power supply using zener diodes has a maximum recommended current of 25 mA. The circuit was found in the May 1966 Radio Electronics magazine.
This sensitive photo-diode circuit with output compatible with TTL logic was found in a 1972 RCA...
This circuit can send signals in both the VHF and FMN bands with a range of a few tens of meters. The...
This circuit was found in a Popular Electronics from the 80s. It is possible to control a relay...