We found this circuit in a Popular Electronics from the 90s. Its purpose is to monitor a power line. The circuit uses optical couplers of the time.
The circuit is from Motorola's Linear Databook from 1990, but the configuration is current because...
Found in a 90’s 73 magazine for radio amateurs, this circuit provides a few milliamps of output...
This is another one of the many versions of this circuit that we have in this section. We found it in...