This circuit is from an 80's Electronic Engineering. The base is a common operating and 4 single integrated voltage comparators. The circuit directly drives 4 indicator LEDs.
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
The configuration shown is from the National Semiconductor Linear Applications Handbook. The...
This shield circuit uses a common CMOS port. The voltage depends on the interfaced logic. The...