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.
Found in a 90’s American publication, this circuit has a voltage gain close to 1, as shown in the...
Using a pair of 741 op amps, this 90 s Radio Electronics circuit works with the previous one. The...
This circuit is from a 1966 Motorola Field Effect Transistors Manual. The circuit makes use of...