A vending machine includes a vend sensor for detecting a completion of a vend operation. The vend sensor includes an electronic circuit connected to first and second sound elements positioned on opposing sides of a product delivery chute of the vending machine. The first sound element directs a sound...http://www.google.de/patents/US7255246?utm_source=gb-gplus-sharePatent US7255246 - Ultrasonic sensor for detecting the dispensing of a product
