We found this transistor circuit in a 1967 General Electric documentation. The circuit makes use of components that can still be easily found on the market, and the SCR may be a 106 type.
This is the traditional configuration of na Astable Multivibrator using two NPN ttransistor....
This circuit was adapted from an Italian publication that no longer exists. This is “Onda Quadra”...
This FET stage circuit was obtained from old American documentation but can be applied to any FET....