Logic probe (CB10024E)

This circuit was found in documentation from the 1980s. Transistors are general-purpose types like the BC548 for NPN and the BC558 for PNP.

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4 transistor radio (CB22168E)
We found this circuit in an English publication from the 60's. The transistors are of germanium of the...
Positive or Negative Voltage Doubler (CB1229E)
In the figure we have an application of an oscillator 4013 as voltage multiplier. It consists of a...
Crystal tester (CB9640S)
The transistors used in this crystal tester are general-purpose types. The circuit was found in...