This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
This circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit is based...
This timer activates a relay after a time interval of up to 15 minutes has elapsed, starting from...
The circuit presented is based on a mechanical tuning fork. The circuit is suggested by National...