Because RFL™ and Hubbell® have a policy of continuous product improvement, we reserve the right to change designs and specifications without notice.
RFL Electronics IMUX Ap-Note 17
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REMOTE ALARM.
Format.
Remote Alarm Indication (RAI) is sometimes referred to as Yellow Alarm or
Receive Remote Alarm (RRA). RAI is defined as an ESF T1 signal containing
a specific pattern within its overhead (FDL) stream. In SF framing, RAI
signal contains a specific pattern in the last bit of each timeslot.
Transmitting RAI affects overhead system management communication in
ESF or payload in SF mode. In E1 format, signaling bits within framing
timeslot carry RAI.
Purpose.
RAI is typically used to signal reception difficulties to other nodes
upstream. Upon detecting receive difficulties, a node may send back RAI
signal to its neighbor. That neighbor will, in turn, send out RAI further down
the line, passing it from node to node through the whole network.
IMUX Implementation.
IMUX Multiplexers take no path-related action upon detecting reception
problems and therefore generally do not support RAI signaling.
For special applications, Common Modules configured as Terminals (but not
as Drop-and-Inserts) offer the ability to generate RAI in response to receive
difficulties.
A Common Module operating in any mode will report RAI reception in
diagnostic counters.
RFL DACS units are designed for maximum switching speed in
teleprotection applications. As such, they do not utilize RAI for path
switching – instead, the much faster method based on UA1 signals is
implemented, as described above.
DACS ports will report RAI reception in diagnostic counters. The signal will
not pass through, since DS1 framing is regenerated in every node.
apnote17 page: 3 of 4 rdw revised 03/26/2002 printed 11/1/2006
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