This two-channel bargraph meter uses a single KAA2281 integrated circuit. Found in the January 1991 issue of Radio Electronics magazine. The stereo circuit drives 2 scales of 5 LEDs.
We find this microphone voice effect in 1992 documentation. The vibration of the relay contacts...
We can also use the 4011 on this CMOS circuit that makes use of a crystal headset. The power...
We found this circuit in documentation from the 1980s. The integrated circuit used is uncommon today,...