Multiplex communications – Wide area network – Packet switching
Patent
1980-11-10
1983-07-12
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
3701104, 371 49, 1791753S, 34082501, H04J 312, H04J 314
Patent
active
043934935
ABSTRACT:
An automatic span line switch for high speed communication lines is disclosed. The apparatus employs an alarm interface unit which is coupled to a service line terminal in order to detect a line failure mode. Upon detection of such a mode, the system operates to modify the parity bit content of the transmitted digital signal in order to provide a unique code to be transmitted to a remote office connected to a near office and indicative of a span line failure. The apparatus automatically proceeds to switch the failed transmission line to a back-up protection line to enable the near location to communicate with the remote location via the back-up line. All control signals transmitted between the locations are implemented by means of unique codes which are generated by purposely modifying the parity bit content in each successive frame of the transmitted digital signal. The system further describes a priority system for preferentially switching higher priority service lines when multiple failures occur. Various other techniques such as manual operation are disclosed to enable manual switching of protection lines during system operation.
REFERENCES:
patent: 3364468 (1968-01-01), Haibt et al.
patent: 3457373 (1969-07-01), Van Duuren et al.
patent: 3715503 (1973-02-01), Jungbluth et al.
patent: 3864533 (1975-02-01), Erlund
patent: 3922495 (1975-11-01), Donohoe
patent: 3983340 (1976-09-01), Lima et al.
patent: 4261054 (1981-04-01), Scharla-Nielsen
"A Digital Transmission Line Switching System", by Takashima et al., Japan Telecommunications Review, Apr. 1980, vol. 22, No. 2, pp. 127-134.
Hill Alfred C.
International Telephone and Telegraph Corporation
O'Halloran John T.
Olms Douglas W.
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