Found in a 1967 Electronics World, this oscillator changes its tone when objects move in their environment. The output is made on a low impedance phone.
Found in American documentation from the 90s, this circuit has a timing system for activating the...
One touch of the X1 sensor and the capacitor C1 charges, causing the power transistor to drive by...
Found in the May 1988 issue of Radio Electronics magazine, this circuit is sensitive to small...