This circuit was found in the September 1984 issue of Radio Electronics magazine. The circuit is based on a 555 and a MOSFET consisting of a flasher that controls a buzzer.
This radio version with a transistor for a crystal phone was found in a Japanese magazine from...
In this circuit of Texas Instruments an incandescent lamp is used as a light source, and lenses are...
This source whose voltage depends only on the zener diode used, can supply currents up to about 3 A....