Found in a Popular Electronics from the 90s, this circuit activates a recorder for automatic recording of telephone calls. The circuit was used with old cassette recorders of the time.
This circuit came out in an American magazine that no longer exists. It's the Electronic...
This circuit can be added to any audio amplifier design, consisting of a good tone control with an...
Using a 741 op amp with symmetrical source, this circuit was found in a 1982 documentation. The...