Specifications

RADring
Installation & Operation Manual Functional Description
3/11/98 12:33 RI/RO Modules Functional Description 2-29
Cable Break Protection
All the TCR repeater models include cable break protection. The cable break
protection function automatically detecting any break in the ring cable and
loops the main path to the back-up path to maintain ring continuity. This is
illustrated in the diagram below, which shows what happens on the ring
segment when one of the cable pairs breaks or is accidentally disconnected
at a patch panel.
For fault tolerance, the TCR automatically shorts the main and backup paths
via an on-board relay when power is off. When a cable fault condition exists,
repeater output is looped back with signal regeneration.
A switch located on the TCR card allows the user to disable this function
when one TCR operates in a link terminated at the other end in a repeater,
or other unit, that uses an incompatible cable break protection method or
no cable break protection at all.
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Figure 2-20 TCR Cable Break Protection
For a situation where the cable connected to the RO connector of site A
breaks, the TCR at site A detects the loss of the phantom signal and performs
the following actions:
1. It loops the main path to the back-up path after passing through the
repeater section. This ensures that the TCR returns a regenerated ring
signal.
2. After looping the main path to the back-up path, the phantom signal to
site B is disconnected causing the main path at site B to be looped back
to the back-up path.
These two operations maintain ring continuity in case of any break in the
ring segment. To notify the user that a fault condition exists, the FLT
indicators of the two TCRs light to indicate the receive signal is missing.