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.
The operational amplifier used in this application is uncommon today. This Raytheon circuit can be...
This conventional bistable power control circuit using triac was found in the June 1970 Radio...
This short-range experimental transmitter emits a signal with many harmonics, without modulation. It can...