Charger protection relay (CB26312E)

This circuit was obtained from an Elektor magazine from the 90s. The circuit is to protect batteries while charging.

High speed alarm (CB20663E)
Found in documentation from the 1970s, this circuit uses an oscillator and a display to warn of...
Simple Siren 555 (CB3862E)
This circuit simulates a low-level siren and can be supplied with voltages from 5 to 15 V....
Frequency Selector 741 (CB16232E)
The filter shown in the figure, using only an operational amplifier, is characterized by allowing 1...