This telephone circuit was found on a 90's EDN. It keeps a flashing LED to indicate that there was a call in your absence. The components admit equivalents.
Found in documentation from the 1980s, this circuit makes use of discrete components of the time....
This battery-powered micropower supply was shown in Radio Electronics magazine in 1991. The...
Found in American documentation from 1968 this circuit is based on discrete components in addition...