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 converts a high impedance signal into low impedance. The circuit has unit gain and...
This project came out in an article of mine (Newton C. Braga) in the Popular Electronics magazine of...
This variable oscillator with crystal was found in a Popular Electronics of the 90s. The circuit uses...