Voltage Regulator (CB14119E)

We found this parallel regulator in a 1973 publication. Transistors admit equivalents and the output voltage can be modified by changing the zener.

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Bipolar Transistor Photo Relay (CB16105E)
The circuit is simple, as it uses only one transistor and a relay that can be MC2RC1 or MC2RC2,...
Logical Level Indicator (CB16958E)
We found this circuit in a 1990 documentation. It works with the power of the digital circuit...
High Pass Filter for High Frequencies (CB12576E)
The filter shown in the figure can operate with frequencies up to several tens of megahertz thanks...