Found in a 90s EDN, this circuit is indicated for power control through a 4-20 mA line. The circuit makes use of optical couplers of the time.
The idea of this circuit from a 1960 publication is simple: we can switch the transistor being...
Using a small speaker as a microphone, this 10-LED circuit was found in the March 1992 issue of...
We found this circuit in a 1977 documentation. The National Semiconductor's LM380 is no longer...