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Alternate Routing for Broadband Cable Circuits

IP.com Disclosure Number: IPCOM000082668D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 39K

Publishing Venue

IBM

Related People

Greenhalgh, RC: AUTHOR

Abstract

Broadband cable networks, for instance CATV systems, are vulnerable to expensive service interruption when a principal link (trunk path) is broken (accidentally or incidental to installation or maintenance service). In systems which contemplate two-way data transmission service on one cable path (from central to users and from users to central), line breakage is an even more serious problem.

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Alternate Routing for Broadband Cable Circuits

Broadband cable networks, for instance CATV systems, are vulnerable to expensive service interruption when a principal link (trunk path) is broken (accidentally or incidental to installation or maintenance service). In systems which contemplate two-way data transmission service on one cable path (from central to users and from users to central), line breakage is an even more serious problem.

A solution described here is to detect the break at the central and operate remote bypass links under central control. The procedure is complicated by the use of different carrier frequencies for the two directions of transmission and, therefore, the use of repeater amplifiers which are frequency/direction dependent.

Circumvention of a cable line fault involves a reversal in signaling relations between affected user terminals and the central. A repeater circuit useful for this purpose is shown in Fig. 1 (symbol R). Transferring the relay contacts reverses the cable connections to the frequency selective amplifiers, so that the frequency and signal directionality of the affected link are reversed. The contacts are remotely transferable by operating the detector-relay circuit.

The application of this in a "looped" link is indicated in Fig. 2. T are user terminals, R1 and R2 are "direction"/frequency selective repeaters (per Fig. 1). S1 is a remotely controllable switch and points A, B and C are exemplary break points. The table below indicates the recovery action for a single break. Cable Break Actuate None None A S1, R1, R2 B S1, R2 C S1.

A break at point A interrupts communication between the central and users downstream of the break, causing the central to initiate recovery procedures. Switch S1 is closed and central signals "upstream" through S1 (at frequency f1). Failing to "hear" from terminals upstrea...