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 is from the National Semiconductor Audio Handbook. The amplifier operates with 6 V...
This is an amplifier that uses a pickup coil placed next to the telephone set and the listening is done in...
The modified Hartley oscillator seen in the figure can generate signals ranging from 3 MHz to 10...