E1 alarms (LOS, LOF, AIS, RAI) [telecom]

Hello, I looked for a clear explanation of E1 alarms such as LOS, LOF, AIS & RAI on the Web but could not come up with anything detailed enough. Could anyone clearly explain me these 4 alarms? What they mean and when they are sent? Any help is very much appreciated. Thanks in advance. Best Regards, Raph

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I'm not quite sure how to answer.

Doing a google on them would have given you what the acronyms stand for in 1000's of places. Mostly its self-explanitory.

ie. LOS = Loss of Signal. You aren't getting signal. LOF = Loss of Framing. Your packets aren't getting through framed correctly. AIS = receiving Alarm Indicator Signal. The far end isn't getting things through framed correctly, and is indicating that back to you. RAI = Remote Alarm Indicator. The far end is getting an error and is signalling that back to you.

There's really not much more to it than that.

To solve almost all of them, mostly involve the telco, because most CPE type gear is so reliable now-a-days. You can reboot the CPE and see if it clears it. If not, its most likely in the telco or the line somewhere.

Ie. if you get a LOS, check the cabling from the hand off. Possibly put a hard loop at the CPE back to the telco. Ask the telco if they see it. If not, have them come out to fix it.

If you are getting a LOF, check to make sure your framing configuration is the same on both sides. If so, ask the telco to come out and fix it. AIS, same thing (although I remember the olden days when CSU/DSU's wedged up and gave blue alarms from time to time).

RAI can be considered the same as the AIS alarm.

Basicly, check to make sure your parameters are correct and involve the telco to fix it. Verify the parameters with them, they should be able to help you.

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Doug McIntyre

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