Charger protection relay (CB26312E)

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

50mA driver (CB20924E)
This ultra-low distortion driver was found in 80's Analog Devices documentation. The circuit has a...
Active Low Pass Filter (CB19802E)
This second-order filter was found in a documentation from the 90's. It can be implemented with...
Voltage Drop Alarm (CB1530E)
This circuit goes into operation producing a sound on a small speaker when the supply voltage...