This circuit was suggested by a 1967 General Electric manual. The waveforms of the generated signals are shown next to the diagram. Equivalent modern SCRs can be used.
With this circuit it is possible to receive and send audio signals simultaneously over the same...
This circuit was found in a Popular Electronics of the 90's. The circuit makes use of common...
We found this circuit in an American documentation from 1964, but it can be easily assembled...