Low battery indicator 555 (CB9551E)

This circuit can operate with different voltages, depending on the zener used. We found it in a 90s American documentation.

Simple 1-transistor receiver (CIR22512E)
This circuit is from 1950, from the time when some still called the crystal triode transistor. The circuit is...
Crowbar protection (CB15434E)
In the circuit shown in the figure, when the input voltage rises to 27 V, the TL431 triggers the...
Full wave rectifier filter (CB7582E)
This circuit was found in a Popular Electronics from the 90s. The power source must be symmetrical...