This receiver was found in a 1924 book by Gernsback. The circuit uses three tubes and is powered by 3 batteries of different voltages, common at the time.
This Schmitt optical trigger with LDR was found in old documentation. The relay must be sensitive, or an...
We found this circuit in the January 1997 Electronics Now magazine. The triac determines the...
This transmitter uses a small loudespeaker (FTE) as microphone and can send the signals to...