A system for the processing of payment and a signal-processing device having a first data port for communication with a case register (10). The signal-processing device (50) also includes a second data port for communication with a display arrangement a third data port for communication with a payment-processing...http://www.google.co.uk/patents/US6536664?utm_source=gb-gplus-sharePatent US6536664 - Method for exchanging information between a cash register and a payment-processing device
