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.
The configuration shown was found in a 1980s American book. The supply voltage is 14 V and the...
With this converter it is possible to receive signals from the 220 MHz band on a 144 MHz receiver....
We found this circuit in a 70s American documentation. The integrated circuits are from that time....