Common Microwave Alarms

LOS-Loss of Signal:

-It is raised when the STM –N level drops below the threshold at which BER of 1 in 1000 is predicted. 
-Causes:

       a. Cable Cut
       b.Excessive Attenuation of the signal
-The LOS state is cleared when two consecutive framing patterns are received.

OOF-Out of Frame:
-OOf occurs when several SDH frames are received with errored framing patterns.

-OOF state is cleared within 250usec when two consecutive SDH frames are received with valid frame pattern.

LOF-Loss of Frame:
-It occurs when OOF frame state exists for a specified time in usec.

-It clears when an inframe condition exists for a specified time in usec.

AIS-Alarm Indicating Signal: 

Its generated to replace the normal traffic signal when it contains a defect condition in order to prevent consequential downstream failures being declared or alarm being raised.

RDI-Remote Defect indication:

-A signal returned to the transmitting terminating equipment upon detecting a LOS,LOF or AIS

-Also called as FERF (Far end receive Failure).

LOP-Loss of Pointer:

-It occurs when N consecutive invalid pointers are received.

-It is cleared when three equal valid pointers or three consecutive AIS indications are received.