The sensor used in this circuit is uncommon today, however equivalent types can be tried. The comparator also supports modern equivalents. The circuit is from 80's documentation.
This circuit was found in the Electronics Experimenter Handbook of 1961. The circuit uses door...
The basis of this circuit is a National Semiconductor operational amplifier that functions as a...
This two-transistor amplifier can be used as power stage for intercom, experimental receivers,...