Door buzzer or alarm (CB20492E)

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

Doorbell with 555 (CB14934E)
This circuit was suggested by a 1979 documentation, and a ceramic transducer can be used in place...
Simplified 2-bit decoder 7400 (CB22422E)
This is the previous version, but with a simplification given by the use of the 7404 and 7408...
Triangular signal generator (CB7596E)
Found in Popular Electronics from the 90s, this generator uses integrated circuits from that time....