This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
CHANDLER, Ariz., June 14, 2017 — New PIC32MM “GPM” microcontrollers (MCUs) are now available from...
This circuit for professional telegraph handlers automatically produces points and dashes. The...