This module includes an optical pass key and has two digits. We found this circuit in a 1995 documentation. Power can be supplied with voltages from 7 to 20 V using the regulator or 5 V directly. More digits can be added to the original project.
12 V battery chargers provide higher unregulated voltage. With the regulator shown, obtained from...
This two-transistor amplifier stage has a feedback network allowing a voltage gain between 10 and...
We published this circuit in a magazine of the 90s, but it is still present by the components it...