This circuit was found in 80's Popular Electronics. The components used are common and the number of indication channels (LEDs) can be changed.
We find this conventional amplifier with complementary transistors in a 1987 documentation. The circuit...
The purpose of this 2000 documentation circuit is to decode SSB (BLU) signals to be audible on...
This circuit changes the wave shape of a square signal according the values of C1 and R1. Other...