We found this circuit in the Radio Electronics Handbook magazine special edition of 1992. The circuit uses an optocoupler as an electronic potentiometer.
This simple half-wave control using an SCR, which may be TIC106, has been obtained from a US...
I found this circuit in an English publication from 1989. This configuration can be mounted with...
This reader with TTL logic compatible output uses an LM139 comparator. The circuit was found in...