This 1968 circuit is intended to switch the polarization of a satellite TV antenna of the time. The circuit is powered by 12 V and the transistors are from that time.
This circuit with unijunction transistors was found in a documentation from the 80's. The trigger...
In this circuit of an old American documentation, the input impedance is the same as the output...
In the figure we have the way to obtain a voltage of 18 V from a 6.3 V transformer with central...