Automatic circuit back-up system

Claim 2

An automatic circuit back-up system for a data communication system, including a private communication line for data communication, a back-up communication line, and back-up communication circuits, with one back-up communication circuit located at a local office and one back-up communication circuit located at a distant office, each of said back-up circuits providing a back-up for said data communication system comprising: periodic message transmitting means located at said distant office for periodically transmitting a message at a predetermined regular period to said local office through said backup communication circuit; and monitoring means for monitoring whether said periodically transmitted message from said periodic message transmitting means at said distant office via said back-up communication circuit is received at said predetermined regular period, wherein a lack of detection of said periodically transmitted message indicates a possible failure of either said distant office back-up communication circuit or of said back-up communication line.

Claim 3

An automatic circuit back-up system as set forth in claim 1, wherein said back-up communication circuit is an integrated service digital network.

Claim 4

An automatic circuit back-up system as set forth in claim 2, wherein said periodic message transmitting means comprises a terminal adapter for calling control in the integrated service digital network and for signal conversion of data for the integrated service digital network.

Claim 5

An automatic circuit back-up system as set forth in claim 3, wherein information necessary for said period message is transmitted by setting in a calling party subaddress information area in a calling control information.

Claim 6

An automatic circuit back-up system located at a local office for a data communication system, including a private communication line for data communication, a back-up communication line, and back-up communication circuits, with one back-up communication circuit located at a local office and one back-up communication circuit located at a distant office, each of said back-up circuits providing a back-up for said data communication system, said system comprising: failure detecting means for detecting either a failure in said private communication line, or a failure in a data circuit-terminating equipment, said data circuit-terminating equipment being located between equipment located at said local office and said private communication line; data communication circuit switching means, said switching means being responsive to said failure detecting means detecting a failure, said switching means allowing for switching a data channel from said private communication line to said local office back-up communication circuit; periodic message transmitting means for periodically transmitting a message at a predetermined regular period to said distant office back-up communication circuit; and monitoring means for monitoring whether a message periodically transmitted from said distant office back-up communication circuit is received at a predetermined regular period, wherein a lack of detection of said message periodically transmitted from said distant office indicates a possible failure of either said distant office back-up communication circuit or of said back-up communication line.

Claim 7

An automatic circuit back-up system located at a local office for a data communication system, including a private communication line for data communication, a back-up communication line, and back-up communication circuits, with one back-up communication circuit located at a local office and one back-up communication circuit located at a distant office, each of said back-up circuits providing a back-up for said data communication system, said system comprising: failure detecting means for detecting either a failure in said private communication line, or a failure in a data circuit-terminating equipment, said data circuit-terminating equipment being located between equipment located at said local office and said private communication line; data communication circuit switching means, said switching means being responsive to said failure detecting means detecting a failure, said switching means allowing for switching a data channel from said private communication line to said local office back-up communication circuit; periodic message transmitting means for periodically transmitting a message at a predetermined regular period to said distant office back-up communication circuit; and monitoring means for monitoring whether a message periodically transmitted from said distant office back-up communication circuit is received at a predetermined regular period, wherein a lack of detection of said message periodically transmitted from said distant office indicates a possible failure of either said distant office back-up communication circuit or of said back-up communication line.

Claim 8

An automatic circuit back-up system as set forth in claim 5, wherein said back-up communication circuit is an integrated service digital network.

Claim 9

An automatic circuit back-up system as set forth in claim 6, wherein said periodic message transmitting means comprises a terminal adapter for calling control in the integrated service digital network and for signal conversion of data for the integrated service digital network.

Claim 10

An automatic circuit back-up system as set forth in claim 7, wherein information necessary for said period message is transmitted by setting in a calling party subaddress information area in a calling control information.