This electronic rheostat with SCR was found in the June 1964 Radio Electronics magazine. The SCR may be a modern type and the 2W potentiometer may be 470 ohms.
Found in an Electronic Design from the 90s, this circuit uses high voltage operationals of the...
This circuit was found in the July 1990 Radio Electronics magazine. It is based on the 3-digit...
The circuit shown in the figure uses two of the four operational amplifiers found on the LM324...