cpe t1 alarm conditions? - 09/05/09 09:56 PM
hello again. i'm back with more t1 questions as our pbx is at it again. we have an asterisk based pbx that uses a digium t1 card. we've been experiencing a large number of alarms all summer long during rain/thunder/lightening storms. our provider is at&t and they finally escalated our issues to their chronic group who seem to be helping but now they believe that there is an incompatibility between our equipment and theirs.
they say that our equipment does not comply with the below t1 alarm conditions.
from what digium is telling me, heir card generates an alarm after 176 continuous zeros while at&t is saying that our equipment should wait 2.5 seconds after the LOS before generating an alarm. i'm not sure what to think as i don't really understand this stuff well enough.
at&t is able to run a test where they change something on their switch which supposedly produces an errored second. this test causes our pbx to generate an alarm which at&t says should not happen as the error was only 1 second and not 2.5 sec. the digium tech that we've been working with tried increasing the number of zeros to 2500 as an engineer told him that 2500 zeros is equivalent to 2.5 sec but we still had the alarm.
hopefully this stuff makes more sense to some of you than it does to me how do other pbx's generate alarms?
below is an excerpt from ACCUNET® T1.5 SERVICE DESCRIPTION AND INTERFACE SPECIFICATION that at&t provided me with.
7.7 Conditions Causing The Initiation Of Carrier Failure Alarms
On detection of an LOS or OOF not caused by an "all ones" or AIS, a rise slope type integration process starts that declares a CFA after 2.5 seconds of continuous LOS or OOF. If the LOS or OOF is intermittent, the integration process shall decay at a slope of from 1/4 to 1/15 of the rise slope during the period when the signal is normal (i.e., for a 1/5 rise slope, 100 msec. OOF would require a 500 msec. of normal signal for an integration counter to reset to zero). The CFA is cleared when no LOS or OOF conditions occur during a variable minimum-clearing time-period which can vary from one second up to fifteen contiguous seconds, depending upon the application.
A CFA state shall cause a "yellow" signal to be transmitted upstream to the far end, via the outgoing bit stream. The "Yellow" CFA signal must be transmitted continuously until the "Red" CFA condition no longer exists. The "Yellow" CFA signal is generated by forcing the second bit to zero in all channels of a DS-1 using the Superframe format. For the Extended Superframe format, a repetitive 16-bit pattern consisting of 8 "ones" followed by 8 'zeros" (1111111100000000) is transmitted continuously for a minimum of one second, over the ESF data link.
A "Yellow" CFA state is activated at a receiving terminal after the "Yellow" signal has been detected and timed. The Yellow CFA signal must be detected in one second or less, even in the presence of a 1 x 10-3 BER. The minimum detection time is 335 msec. for the SF format and 28 msec. for the ESF format. The recommended detection/clear algorithm for the ESF format is, "a Yellow CFA shall be declared if the Yellow CFA signal pattern occurs in at least seven out of ten contiguous 16-bit pattern intervals. A Yellow CFA is cleared if the Yellow CFA signal pattern does not occur in ten contiguous 16-bit signal pattern intervals."
An AIS signal is detected by monitoring for both OOF and "all-ones" conditions. The "all-ones" condition must be detectable in the presence of a 1 x 10-3 BER. An "AIS CFA" condition is declared when both OOF and "all-ones" conditions are present at the same time. The AIS condition clears when either the OOF, or all-ones, or both conditions clear.
Since the AIS does not contain framing information, an AIS will initially activate a "Red" CFA state. If the incoming AIS signal persists after the 'Red" CFA state is activated, an "AIS CFA" state should be declared. An "AIS CFA" state is cleared when the condition which triggered the "Red" CFA state is cleared.
they say that our equipment does not comply with the below t1 alarm conditions.
from what digium is telling me, heir card generates an alarm after 176 continuous zeros while at&t is saying that our equipment should wait 2.5 seconds after the LOS before generating an alarm. i'm not sure what to think as i don't really understand this stuff well enough.
at&t is able to run a test where they change something on their switch which supposedly produces an errored second. this test causes our pbx to generate an alarm which at&t says should not happen as the error was only 1 second and not 2.5 sec. the digium tech that we've been working with tried increasing the number of zeros to 2500 as an engineer told him that 2500 zeros is equivalent to 2.5 sec but we still had the alarm.
hopefully this stuff makes more sense to some of you than it does to me how do other pbx's generate alarms?
below is an excerpt from ACCUNET® T1.5 SERVICE DESCRIPTION AND INTERFACE SPECIFICATION that at&t provided me with.
7.7 Conditions Causing The Initiation Of Carrier Failure Alarms
On detection of an LOS or OOF not caused by an "all ones" or AIS, a rise slope type integration process starts that declares a CFA after 2.5 seconds of continuous LOS or OOF. If the LOS or OOF is intermittent, the integration process shall decay at a slope of from 1/4 to 1/15 of the rise slope during the period when the signal is normal (i.e., for a 1/5 rise slope, 100 msec. OOF would require a 500 msec. of normal signal for an integration counter to reset to zero). The CFA is cleared when no LOS or OOF conditions occur during a variable minimum-clearing time-period which can vary from one second up to fifteen contiguous seconds, depending upon the application.
A CFA state shall cause a "yellow" signal to be transmitted upstream to the far end, via the outgoing bit stream. The "Yellow" CFA signal must be transmitted continuously until the "Red" CFA condition no longer exists. The "Yellow" CFA signal is generated by forcing the second bit to zero in all channels of a DS-1 using the Superframe format. For the Extended Superframe format, a repetitive 16-bit pattern consisting of 8 "ones" followed by 8 'zeros" (1111111100000000) is transmitted continuously for a minimum of one second, over the ESF data link.
A "Yellow" CFA state is activated at a receiving terminal after the "Yellow" signal has been detected and timed. The Yellow CFA signal must be detected in one second or less, even in the presence of a 1 x 10-3 BER. The minimum detection time is 335 msec. for the SF format and 28 msec. for the ESF format. The recommended detection/clear algorithm for the ESF format is, "a Yellow CFA shall be declared if the Yellow CFA signal pattern occurs in at least seven out of ten contiguous 16-bit pattern intervals. A Yellow CFA is cleared if the Yellow CFA signal pattern does not occur in ten contiguous 16-bit signal pattern intervals."
An AIS signal is detected by monitoring for both OOF and "all-ones" conditions. The "all-ones" condition must be detectable in the presence of a 1 x 10-3 BER. An "AIS CFA" condition is declared when both OOF and "all-ones" conditions are present at the same time. The AIS condition clears when either the OOF, or all-ones, or both conditions clear.
Since the AIS does not contain framing information, an AIS will initially activate a "Red" CFA state. If the incoming AIS signal persists after the 'Red" CFA state is activated, an "AIS CFA" state should be declared. An "AIS CFA" state is cleared when the condition which triggered the "Red" CFA state is cleared.