This telephone recording circuit was found in the June 1979 issue of Radio Electronics magazine. The components are common at the time and the power is supplied by the power grid.
This RF amplifier step has a dynamic range of 140 dB and can amplify signals from 0.5 to 40 MHz....
This circuit produces a square wave signal with the frequency determinated by R1 and C1. The upper limit...
This circuit was found in Motorola's 1968 documentation. The SCRs are then replaceable with...