This resistance meter was found in an English documentation from 1989. The operational amplifier admits an equivalent and the transistor can be a BC558 or BC559.
This voice scrambling scrambler was published in the August 1982 issue of Radio Electronics...
This is the traditional configuration of an inverter amplifier with 100 voltage gain and...
This circuit was obtained in a 1980 publication. The transistors can be BC548 or 2N2222. The...