Found in 1980s Electronic Engineering, this circuit uses common phototransistors as sensors. The circuit is CMOS using an integrated 4011.
The circuit with a common operational amplifier uses a zener as a reference. The circuit is from...
This circuit was found in a 90’s Popular Electronics. The circuit is used to analyze noise in...
This 1989 circuit activates a protection relay if one or two phases are missing from a three-phase...