This small transmitter appeared in the March 1989 issue of Radio Electronics magazine. The two-transistor circuit used an electret microphone and had a range of a few dozen meters.
This oscillator with crystal for overtone operation was found in an old American documentation. The coil...
In the figure we have a basic PLL circuit with the LM567 or equivalent. The circuit is from a 1977...
The A3906 integrated circuit from Allegro MicroSystems (www.allegro.com) consists of a single...