)
We found this circuit in the November 1992 issue of Radio Electronics magazine. The 30V power supply must be symmetrical and preamplification stages are included.
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,...