Door buzzer (CB7560E)

This buzzer with the 555 was suggested by a Popular Electronics from the 90s to be used as a doorbell. The circuit is battery powered.

Dual Driver (CB25549E)
This circuit drives symmetrical loads through a single transistor. The circuit is from a Radio...
Automatic Safety Flasher (CB5207E)
The transistors of this circuit can be BC548 for NPN and BD136 for PNP with load up to 500 mA. The...
Electronic Relay (CB504)
circuit is used to increase the sensivity of a relay. A 50 to 100 mA relay can be triggered with...