Found in a 1924 Gernsback publication this circuit uses 4 batteries for power and loop antenna. Listening is over a high-impedance type earphone or loudspeaker common at the time.
This circuit can be installed inside a toy space gun to produce a “Phaser” effect. The circuit is from...
This circuit was found in a 1988 publication. The circuit is an alarm with interrupt sensors that...
The frequency in this circuit is adjusted by P1 and given by C1. Short pulses, as the ones...