This well-designed bistable circuit was found in a 1970s documentation. Transistors can be current types and germanium diodes. The voltage depends on the logic used and can be made with 5 V.
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This receiver for the mid-wave band was found in a documentation from the 60's. The transistors are made...
In the figure we have a symmetrical power supply stabilized by a zener diode. Transformer and...
This circuit is a digitally controlled variable capacitor. We found it in American documentation from...