This circuit for analog telephones from the 90s was found in documentation from the time. It lights up a remote LED when the extension is in use.
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This circuit of a 1991 PE Hobbyst Handbook allows the brightness of the incandescent lamp to be...
This simple operational amplifier tester was published in the November 1987 issue of Radio...