Title: Redundant memory for point of sale system

Abstract: A point of sale system having an active and a spare data processing system, each including separate read/write memories, with only one of the systems being active at a given time, but with the active system being able to selectively acquire data from the read/write memory of the spare system upon start-up and including means for verifying which read/write memory of the active or the spare system contains valid, most current data which is then transferred to whichever system is the active system, the read/write memories of each of the two systems having a built-in generation number counter which is incremented by one whenever either the data of the inactive read/write memory is caused to be transferred to the active read/write memory or whenever the counts in the generation number counters of both read/write memories are equal, this change in the generation number counters taking place only at the start-up of the system.

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Inventors: Fairman, Bruce A. (Scottsdale, AZ, US)
Durney, G. Ray (Mesa, AZ, US)
Taylor, Robert G. (Mesa, AZ, US)

Application Number: 791139
Filing Date: 1977-04-26
Publication_date: 1979-09-25
Assignee: International Telephone and Telegraph Corporation (New York, NY)
Primary Class(es): 705/20
Other Classes:
US Patent Ref:

3377623	Apr, 1968	Reut et al.	364/200.
3636331	Jan, 1972	Amrehn	364/200.
3864670	Feb, 1975	Inoue et al.	364/200.
3866182	Feb, 1975	Yamada et al.	364/200.
3882455	May, 1975	Heck et al.	364/200.
3898621	Aug, 1975	Zelinski et al.	364/200.
3921141	Nov, 1975	Wilber et al.	364/200.
3946220	Mar, 1976	Brobeck et al.	364/200.
4032899	Jun, 1977	Jenny et al.	364/200.

Other Refs:
Primary Examiner: Shaw, Gareth D.
Assistant Examiner: Eng, David Y.
Attorney: Kristofferson; Thomas E.