This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an automatic transmission circuit for telegraphy. The circuit is TTL.
The sensor of this circuit is an NTC with a resistance between 200 and 1000 ohms. The resistor R1 must...
Found in a 90s Radio Electronics, this circuit uses a ceramic capacitor (C1) as a sensor. The...
This two-tone alarm siren was found in the January 1975 issue of Radio Electronics magazine. The...