This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
This 80's circuit has an input resistance of the order of 880 M and gain 10, using operational...
We found this circuit in the Audio Handbook of the National Semiconductor of 1977. The circuit is used...
Published in 1988 in Hands-On Electronics, this circuit converts the 12 V of a battery into 120 V...