The timing steps of this circuit are indicated by a 7-segment display. The circuit was found in documentation from the 90s. The capacitor next to the 555 determines the timing steges.
This circuit is one of many that the reader can find in this section for testing crystals. The...
I found this circuit on a December 1976 Radio Elettronica. The Italian magazine no longer exists, but...
June 2017 - Mouser Electronics has in stock the new AC Metallized Polypropylene Film Capacitors...