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 simple oscillator with just one transistor has a frequency determined by the characteristics of the...
This Zero Crossing Detector was found in a 1972 RCA manual, but it can be made using any modern...
The circuit shown was found in a Japanese publication from the 1960s. Transistors can be...