Patent
1973-11-13
1976-12-14
Claffy, Kathleen H.
179 15A, H04J 300
Patent
active
039977277
ABSTRACT:
A synchronous digital data switching apparatus in the form of a PABX telephone system is disclosed. The extension telephones of the apparatus are fully digital and transmit synchronous digital data to the switch. The switch includes a detector for scanning the inlets and remains connected to each inlet until the state of that inlet or a code is detected. Consequently the size of the switch is limited by the speed of available technology as all inlets must be examined within the minimum signalling period of any inlet. The telephones continually transmit digital data relevant to their state and also transmit digital codes during signalling. The apparatus is processor controlled and a switch memory for setting up connections between any inlet and any one or more outlets is time shared between the switch and processor. The processor receives information from the detector relevant to the condition of an inlet and compares that information with information from the switch memory relevant to the condition of that inlet on the previous scan. Service tones for the apparatus are digital and are inserted at inlets to the switch and on a single highway within the switch during particular connections. A switch memory utilizing abbreviated addressing to save memory is also disclosed.
REFERENCES:
patent: 3073907 (1963-01-01), Alterman
patent: 3111560 (1963-11-01), Gatzert
patent: 3603737 (1971-09-01), LeDorh
patent: 3632883 (1972-01-01), Aagaard
patent: 3649763 (1972-03-01), Thompson
patent: 3678205 (1972-07-01), Cohen et al.
patent: 3737586 (1973-06-01), Johnson
patent: 3740480 (1973-06-01), Krupp
patent: 3781485 (1973-12-01), Woodward
patent: 3860761 (1975-01-01), O'Neill
Geisler Trevor Ross
Harwood Keith
Platts John Charles
Sheahan Christopher Gerald
Claffy Kathleen H.
L M Ericsson Pty. Ltd.
Popek Joseph A.
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