E)
This audio filter was found in the August 1993 issue of Radio Electronics magazine. It cuts low and high frequencies corresponding to rumble and scratch noises that occur on turntables.
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,...