Found in a 1960s documentation, this circuit uses a transistor to drive a relay as well as a set of neon lamps with high voltage power supply.
This circuit was suggested by Motorola's 1993 Linear Interface ICs. Equivalent operational amplifiers...
This timer, from an old American publication, uses indicator lamps, but can be modified to use...
This low-pass circuit was found in the December 1990 issue of Radio Electronics magazine. The...