Vending machine control with improved vendor selector switch detection and decoding apparatus

Abstract From the Canadian patent

A vending machine control with an improved vendor selector switch detection and decoding circuit is described which detects and decodes the closure of selector switches in a vending machine utilizing a low cost decoding arrangement. Each selector switch is associated with a corresponding impedance in a keyboard network to that a unique impedance is presented on a keyboard decode line from the keyboard network. Decode circuitry and a decode algorithm are also disclosed for a period based decoding scheme which compensates for various tolerances and environmental effects.