Abstract: A fault tolerant, magnetic disk drive array with error detection and correction. The present invention performs vertical parity checks and one or two additional diagonal parity checks on a data stream as it is read into a disk drive array. The results of these "read-in" parity checks are stored in either two or three redundant disk drives. Upon read out of the data stream from the disk drive array, similar "read-out" parity checks are performed on the data. Based upon a comparison of the "read in " and read "out" vertical and diagonal parity checks, corrupted data can be detected and corrected.

Abstract: A communications terminal and network of such terminals offering simultaneous real time or delayed document and voice services through a host processor with overall control, including accounting functions based upon credit card billing. Document services include facsimile, copying, electronic mail and document storage. Voice services include voice mail, and telephone. Real time document handling is achieved using a high speed coprocessor to implement a data compression-decompression algorithm. A pair of common communications channels, such as public telephone subscriber network lines, allow connection of the terminal to a hub. A plurality of interconnected hubs allow wide area availability of document and voice communication services.