Door buzzer or alarm (CB20492E)

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

TV remote control (CB24274E)
This circuit from a Radio Electronics from December 1974 was used in color televisions of the...
Light Alarm (CB10330E)
This circuit was obtained in a 1985s English magazine. The circuit can still be assembled with...
Door buzzer or alarm (CB20492E)
This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose...