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Models 2616RC, 3096RC & 3196RC Admin Reference Guide 20 • T1/E1 Link
Near end or far end sending AIS (Alarm Indication Signal (AIS) Failure)
The Alarm Indication Signal failure is declared when an AIS defect is detected at the input and the AIS defect still
exists after the Loss of Frame failure (which is caused by the unframed nature of the all-ones signal) is declared.
The AIS failure is cleared when the Loss of Frame failure is cleared.
Near End LOF or Red Alarm (Loss of Frame Failure)
Occurs under the following conditions:
• For T1 links, the Loss of Frame failure is declared when an OOF or LOS defect has persisted for T seconds,
where 2 ð T ð 10. The Loss of Frame failure is cleared when there have been no OOF or LOS defects dur-
ing a period T where 0 ð T ð 20. Many systems will perform hit integration within the period T before
declaring or clearing the failure (for more information, see TR 62411 (16)).
• For E1 links, the Loss of Frame Failure is declared when an OOF defect is detected.
Near End Loss of Signal (Loss of Signal Failure)
Occurs under the following conditions:
• For T1, the Loss of Signal failure is declared upon observing 175 ±75 contiguous pulse positions with no
pulses of either positive or negative polarity. The LOS failure is cleared upon observing an average pulse
density of at least 12.5% over a period of 175 ±75 contiguous pulse positions, starting with the receipt of
apulse.
• For E1 links, the Loss Of Signal failure is declared when greater than 10 consecutive zeroes are detected (see
O.162 Section 3.4.4).
Near End is Looped (Loopback Pseudo-Failure)
The Loopback Pseudo-Failure is declared when the near end equipment has placed a loopback (of any kind) on
the DS1. This allows a management entity to determine from one object whether the DS1 can be considered to
be in service or not (from the point of view of the near end equipment).
E1 TS16 AIS (TS16 Alarm Indication Signal Failure)
For E1 links, the TS16 Alarm Indication Signal failure is declared when time-slot 16 is received as all ones for all
frames of two consecutive multiframes (see G.732 Section 4.2.6). This condition is never declared for T1.