This circuit is from a 1992 publication and is based on CMOS technology. The circuit is powered by a 6 V source and the displays are of common cathode.
The LM121 integrated circuit is no longer common in our market, with more modern equivalent...
August 2016 - It can be found at Mouser Electronics the new sensors light to digital OPT3002 from...
We found this circuit in a 1991 documentation. Instead of the LEDs, the circuit can be modernized with...