This rectangular signal generator was found in an Electronics World of 1966. The transistors are from that time and modern equivalents can be tested.
This circuit was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit produces a square wave signal with the frequency determinated by R1 and C1. The upper limit...
In the figure we have the circuit of an amplifier for alternating signals with 10 times gain,...