Door buzzer or alarm (CB20492E)

This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose NPN.

Timed Emergency Light (CB16507E)
We found this circuit in a 1998 documentation. The circuit can also be used as a minutery...
Integrated Transmitter without Coil (CB14821E)
The TAA131 used in this circuit is not very easy to find today, but an equivalent low power audio...
Treble Control (CB24006E)
These three circuits have different treble responses. We found them in the February 1970 issue of...