Patent US 5,079,740

A system and method for providing an automatic back-up primary terminal for a cluster of secondary terminals. The primary terminal and the back-up primary terminal are coupled over a communications network to the secondary terminals so that data from the secondary terminals is received simultaneously at both the primary and back-up primary terminals. Either the primary or the back-up primary terminal can function as the active provider of services to the secondary terminals. When either one of the primary terminals becomes inoperative, control is automatically switched to the other one which becomes the active provider of the services. The primary terminal which is the active provider of services keeps a log file (on a disc file) of special data which is to be "backed up" or transferred to the other primary terminal when that other primary terminal becomes operative again. The special data, in the embodiment described, related to price look-up and inventory totals associated with retail terminals.