Found in a 1970 documentation, this circuit makes use of 741 operational amplifiers that are common today. Note that the power supply must be symmetrical.
In the figure we have the way to use the transistors of an old-paired pair as a trigger circuit. The...
We found this synchrodyne receiver for the medium or short-wave band in the Radio Electronics...
This old circuit, from a 1992 documentation, was used with tape recorders acting as playback. The...