Method and apparatus for transmitting a digital information signal and vending system incorporating same

Abstract

A cashless business transaction system (e.g., a vending system, a material tracking system, or a highway toll system) incorporates a method and apparatus for transmitting a digital information signal. A signal generator ( ) generates a constant frequency signal. A phase modulator ( ) varies the instantaneous phase of the constant frequency signal to represent digital information, thereby producing a phase modulated signal ( ). A tuned resonant circuit ( ) filters and averages the phase modulated signal to produce a simulated FM signal, and transmits the simulated FM signal via its antenna ( ). One such business transaction system (e.g., a vending system) incorporates such a transmitter to facilitate transmission of billing information from a device located within a substantially electrically shielded environment. Another such business transaction system preferably incorporates such a transmitter to facilitate half-duplex transmission of digital information regardless of whether or not the digital information is transmitted from a device located within a substantially electrically shielded environment.