In one aspect, the present invention is directed to a cash register machine, comprising: an expected currency calculator; and an actual currency calculator, employing one or more sensors for the operation thereof. The sensor(s) may detect whether a banknote is placed into a compartment of the machine,...http://www.google.es/patents/US20100044426?utm_source=gb-gplus-sharePatente US20100044426 - CASH REGISTER MACHINE
