Patent ID: 7856289

Claim:
A vending machine for dispensing at least one vending item, comprising: a vending component within the vending machine; circuitry for supplying power to the vending component; an audio signal detector configured to detect a sound generated by a physical dispensing of the at least one vending item, the detected sound indicating that the at least one vending item is being dispensed, and the audio signal detector configured to transmit a dispensing event signal in accordance with the detected sound; and a controller for receiving the dispensing event signal from said audio signal detector and for controlling said circuitry to transition between first and second operating modes based on the received dispensing event signal, wherein in the first operating mode the circuitry supplies power to the vending component and in the second operating mode the circuitry cuts off power to the vending component, wherein the audio signal detector includes a noise compensation unit that compensates for ambient noise, the noise compensation unit dynamically changing a level of the detected sound that indicates a dispensing event based on changes in ambient noise level, the noise compensation unit including first and second amplifiers such that the second amplifier is coupled to an output of the first amplifier to generate a feedback signal for one input of the first amplifier, a level of the feedback signal corresponding to the ambient noise level.