Troubleshooting Legend/Magix T1 issues

PRI TROUBLESHOOTING- D Channel Inoperative

1)    Check Permanent alarm table for any other T carrier related alarms (i.e., DS1 loss of  Signal). If present trouble shoot those alarms. (See Errors below)
2)    Verify the status of the network and the DTE on the CSUs  LEDs. Troubleshoot
accordingly if either side shows a problem . (On 3160/3164 CSU, verify that the LEDs are assigned to DTE.
3)   Verify that the CSU channels are mapped and Programmed for DATA
4)   Verify that the CO (Central Office) switch selection in the PRI programming is correct i.e., B8ZS/ESF
5)   Verify that the Magix TEI is set for 0 ( Lines/Trunks>PRI>Protocol>TEI.)
6)   Demand Test the 100d module
7)   If the T carrier is set to AMI, verify that the CO (Central Office) has inverted the D-channel
8)   Attempt to reset the PRI by disconnecting the cable at the 100D, wait 1 minute and then reconnect the cable
9)   Run the CSU Loop back test to a 103 loop back or loop back plug towards the Magix at the Smart jack
10) Verify that the Technician , while programming, did not program the PRI, then reprogram the T1 and then reprogram back to PRI. If so, system erase the Magix and re program the PRI and retest.
11) Cycle Power on the Magix
12) Verify the configuration of the CO (Central Office ) switch with the CO Technician
A)    If the CO is a 5ESS make sure they are running ATT Custom
B)    If the CO is a DMS 100 and/or DMS 250 make sure they have Variant= NTNAPRI, (L1 flags in Trunk Sub Group = Yes) If set to ‘NO’ the D channel will act problematic.
   C)    If DSX600E make sure Profile =p250.
13) Have the CO restart the PRI and determine why the D channel didn’t come up.
14) Verify the continuity for the T by having the CO run a stress test to a loop back at the CSU
15) Replace the 100d
16) Replace the Processor
17) At  this point the problem has to be a Network issue.



Cannot dial international long distance calls.
* on some PRI facilities, it is necessary, in the Special Service Table, to change
the “Type Of Number” entry for international format, from ‘international’ to ‘national’

Can Call local, but are unable to dial any long distance numbers
Check the “Digits to Delete” section of the Special Service table. If there are digits being deleted, change all values to 0.  These digits send the dialing prefix ( 011, 01,1, etc) so the T1 carrier knows how to process the call, and are needed by some (mostly local) providers.  If the T1 is maintained by a long distance company like AT&T or Sprint, the prefix is not generally used so they are deleted.

Can dial local and long distance toll calls, but are unable to call toll-free (800, 888 etc) and / or intra-lata long distance.
It may be necessary , under some circumstances, when all of the other Special Service Table entries are set at default (3 3 2 2 1 0 0 0), to change entry 5 to a 1.  Why this works is not documented, but has cleared trouble on several occasions.

Everything in programming looks  good , but still can’t call in or out. Provider may report That they cannot see the ‘D’ channel.
Verify with the vendor that the “Switch Type” is correct, and that the appropriate protocol is being used. The protocol for the DMS-100 and other Nortel switches is NTNAPRI.  The protocol for 5ESS and other AT&T switches is AT&T Custom. Also for DMS 100 switches the L1 flag in the ‘Trunk Sub-group’ table is to be set for ‘Yes’.

After a reset of the 100DS1 card a cold start of the switch or a brief disconnection of cabling for loop back testing, the T1 appears to come back up but calls cannot be made in or out.
When a PRI connection is lost (for whatever reason) the T1 will normally reset itself and rebuild the connection to the Magix.  To do this, the “D” channel is established first and then the “B” channels are brought up either one at a time , or globally(all at once).  This is particularly significant because the success of the restart is entirely switch dependent.  If the Switch is a DMS-100, DMS-250, or DEX600E, it expects Nortel protocol.  Whenever the switch is reset, this protocol specifies that the first Layer-3 “D” channel message must be a global RESTART message (bringing the “B” channels up all together) sent from the network switch to the Magix.  If the switch is a 4ESS or 5ESS, it expects AT&T protocol. Whenever the switch is reset, the first Layer-3 “D” channel message sent from the Network switch to the Magix must be a “ B” channel SERVICE message (bringing the ‘B” channels up one at a time)

This is a newly provisioned service and  unable to call in or out.
***Print PRI information. IF the customer confirms that the PRI service is relatively generic and id utilizing Direct Inward Dial, here a some things to take a look at.
1)Is the switch type entered and correct?
2)Is the number of “B” channels entered the same as the number of lines?
3)Is there any number entered in the TestTelNum Field? If so delete it.
4)Are they using Direct Inward Dialing? If so, make sure Incoming Routing is set to By Dial Plan.
5)Look at entry ‘0’ in the Call-by-call Service Table. Are the Patterns 0-9 entered?
6)Is the NtwkSer under Entry ‘0’, for the call by call service table, set to no service?
7)Is the NtwkSer under Entry ‘0’ , for Dial Plan Routing Table, set to “Any Service”?

Errors and Alarms:

**These error codes are most commonly seen with T1**

Error Description Action Quick Checks
0c03 All TTR’s Unavailable Check to see if more TTR’s can be added Test TTR’s
2C01 T1 Access Violation Check T1 Programming.
Check CSU programming
Check T1 Programming.
Check CSU programming
6c01 DS1 Loss of Signal Usually not Magix.
Usuall Network.
Make Test calls, OK?
Check T1 facility.
Cables Plugged in?
6c02 DS1Blue Alarm Usually not Magix.
Usuall Network.
Make Test calls, OK?
Check T1 facility.
Cables Plugged in?
6c03 DS1 Red Alarm Usually Framing Make test calls.
Check T1 Programming.
Check CSU Programming.
Cables plugged in?
Check T1 facility
6c04 DS1 Yellow Alarm Usually Network, far end lost sync. Make test calls.
Check T1/CSU Programming.
6c05 DS1 loss of Multiframe Usually Network.
Service on Link, lost.
Check T1 facility.
Check CSU lights.
Check Programming.
6c06 DS1 Remote Multiframe Usually none, Network loss of Multiframe. Check T1 facility.
Check CSU lights.
Check Programming.
6c08 DS1 Minor Alarm Usually Network, Bit error rate exceeded. Check T1.
Check network facility.
6c009 DS1 Misframe Alarm Usually Network misses reached 18. Check T1 facility.
Check CSU lights.
Check Programming.
6c0A DS1 Slip Alarms Network or Magix Clocking Slips, reached 88 Check Programming.
Check T1 facility
6c0B Hardware Inoperative BusyOut/Restore slot Check Slot status in maintenance.
7404 Stuck ringing None on T1 Check Programming.
Check T1 facility
7801 Not in Normal OP Mode None on T1 Test T1 Card.
Reset/Restore Slot
7808 Test Result Registrar bad Reset/Restore Slot Reset/Restore Slot
8403 No External Release Usually Network communication problem between CO and Module Check CSU Programming.
Check T1 facility
8404 On Hook Before Wink Usually network or dialing trouble on wink delay of Tie lines Check Bad cable.
Test Card/Module
Check T1 Programming.
Tie Line Programming.
8405 On Hook before Ready Usually network or dialing trouble on wink delay of Tie lines Check Bad cable.
Test Card/Module
Check T1 Programming.
Tie Line Programming.

Quickie T1 troubleshooting

1.    Determine if the problem is with the SPAN, PBX or the distant switch (PBX, 4E/5E, etc..)
2.    If the SPAN is up (No DS1 Alarms) and incoming and outgoing calls are being made; but:
-calls are being disconnected
-there are fax transmission problems
-there are analog data (modem) transmission problems
Suspect Line Coding mismatch between AMI vs. B8ZS in the network or between network and the CSU
A)    Verify that all SPAN components  in the network are configured for the same line coding
B)    Call the provider of the T1 service and have SPAN STRESS tested through the Smart Jack and the CSU
C)    Verify the line coding configuration options in the CSU/Magix programming

3.    The SPAN is up (No DS1 alarms) BUT calls CANNOT be made.
A)    Verify that the trunk type ( tie , loopstart/groundstart etc..) and the signaling type ( WINK in/ WINK out etc.) in the local and remote switches are configured the same.

4.    SPAN down (DS1 Alarm present)
A)    Verify there is an indication of a DS1 signal at the Smart Jack, CSU and PBX
B)    Verify options of the CSU and the Magix
C)    Make appropriate loop backs to isolate the problem into the PBX, CSU, cabling or Network. Check cabling for intermittent conditions by moving to test for poor physical connections


Causes of Red and Yellow alarms are:

  • Synchronization can be lost
  • Repeaters might send a 1 instead of a 0
  • Hits on the line can change a Bit

Understand that these alarms are for serious problems that affect the entire T1 bit stream.

A Red alarm is initiated by the local DS1 board when the framing on the incoming DS1 bit stream is not recognizable. This would also be the case if too many framing bits are in error ( 3 out of 16).  Upon initiation of a Red alarm, the switch sends a Yellow alarm code (bit 2 set to a “0” on all 24 channels with the D4 framing or alternating bytes of eight “1”s followed by eight “0”s on the embedded FDL (4 Kbps “Facility Data Link” with ESF) on the outgoing DS1 bit stream.  In a nutshell- If my switch finds its out of sync it presents a Red alarm to the other switch. The other switch now knows I’m in trouble.  It will not send the alarm right away. It will first try to reestablish synchronization, if it can’t in 2.5 seconds it sends the alarm

A Yellow alarm is transmitted to the distant end switch to indicate that there is a Loss of Signal, RED ALARM or BLUE ALARM at that location.  The format of the yellow alarm code employed is dependant on the type of framing. For D4 framing, the yellow alarm code is recognized as bit 2 of each channel set to zero (“0”).  For ESF, a Yellow alarm is recognized as alerting bytes of eight “1”s followed by eight “0”s on the embedded 4 Kbps data link (FDL).  In a Nutshell- I’m sending stuff but the other end is in trouble. The other end has received a bad DS1 signal and is in a RED alarm stat.

A Blue alarm is recognized as a DS1 signal comprised of a continuous stream of Unframed “1”s.  Depending on its options,  a CSU will generate a Blue alarm ( AIS=Alarm Indication Signal) also know as a keep alive signal when it looses the DS1 signal from its attached DS1 module/board.  The end receiving a Blue alarm sends a Yellow alarm to the distant end. In other words a Blue alarm signals the next terminal ‘downstream’ that a failure or alarm Condition has occurred ‘upstream’. In a Nutshell- Network originated signal when the far end is down. This will almost always be the network, unless the CSU gets unplugged from the Smart Jack.

Examples of ALARM Conditions
·    If the TRANSMIT side between the Magix DS1 board and the CSU is open, the 4E (CO side) will go into BLUE (AIS) alarm and SEND a YELLOW towards the Magix.  The Magix would show a YELLOW alarm.  This indicates the Magix RECEIVE side is good.
·    If the Magix RECEIVE side is open between the CSU and Magix DS1 card , the Magix Sends a YELLOW to the 4E (CO). The CO would see the Yellow and the Magix would indicate LOS (Loss of Signal) Alarm.
·    If the 4E (CO) goes into a RED alarm it will SEND a YELLOW and the Magix would see a YELLOW alarm in the error log.
·    If the Magix DS1 board goes into a RED alarm we will send a YELLOW to the 4E (CO) that sees the YELLOW. The Magix error log will show a RED alarm.

A misframe could be programming. ESF/D4 don’t match on both ends or switch or CSU programming is wrong.

A Loss of Signal is a condition where no pulses or too few pulses (digital signal) are being received by the DS1 board from the Network.

Additional T1 troubleshooting and information:

Problem Reported:

Check Magix For:

No Wink on Incoming Number of TTRs
Test TTRs. Tie or DID wink start programming
Slipping Magix Clock Settings.
CSU Clock Settings.
Misframe Magix Frame Format Options.  CSU frame options.
Dead Air Check Magix Errors
Caller hears dial tone Check Tie programming and Verify with vendor that their programming is correct.
Number of TTR’s?  Test TTR’s
Echoing Check Tie Line prog.
Tie lines should be set for Tie Toll if C.O. is Involved.
No Echo suppression from C.O.
Restricted Set Can Call Out Check Tie line programming.
Tie Lines hsould be TIE TOLL if CO is involved.
TIE PBX ingnores restrictions.
Noise/ Static Generally Clocking/ External modules.
Bad MLX card could Cause this or 016 tip module next to card could cause this.
Can’t Put calls on Hold, or transfer 3 has no effect Answer supervision not being received.
Answer supervision program in CO
Cut Offs Check Magix Clock settings Check Magix Suppression if Correct refer toNetwork provider

Useful Network Terms

DACS — Digital Cross Connect in Central Office, Compression Point, Requires programming in C.O., if it is wrong won’t pass signaling bits to us ( No wink seen by Magix)

Stress Test — A test performed by Network Provider while T-1 is down
Low density stress test is all 0’s pattern
High density stress test is all 1’s pattern
Random density stress test is 1’s and 0’s

MIONOP — Tie line emulation with immediate seizure and no Digits sent.  In Magix this is Tie Line with Auto IN

ICOPNOP — Tie line emulation with wink start and no digits Magix will not match this, therefore can’t do it.

Dial Tone Start — Tie line emulation with immediate seizure, waits for dial tone before collecting  digits.  In Magix it is the same programming but if we use ARS this may fail.  Magix prefers Tie lines with Wink start.

Loop Back — Smart Jack loop back test service from the C.O. to the Smart Jack
CSU loop back test from DS1 card to loop back point
DTE loop back test towards the Magix

DNIS — Dialed Number Identification Service ( Works like DID)

ISDN — Integrated Service Digital Network either BRI ( Basic Rate Interface) or PRI (Primary Rate Interface)

3160 CSU Commonly used Options

To check Frame Format and Suppression for both the NET and DTE
1    Press Double Arrow UP
2    Select Config-Active-Edit-DTE-Next
3    Select ESF or D4
4    Hit Next
5    Select B8ZS or AMI-ZCS
6    Single UP arrow
7    Select Net
8    Select ESF or D4
9    Hit next
10    Select B8ZS or AMI-ZCS
11    Hit Double arrow UP
12    If options were changed, it will prompt you to save
13    Hit Active

To Check Clock Source
1    Hit Double UP arrow
2    Select Config- Active- Edit
3    Hit RIGHT arrow Twice
4    Select GEN- Next
5    Select NET or DTE
6    Hit Double UP arrow
7    If options were changed, it will prompt to save
8    Hit active

To Display Current Channel Configuration
1    Hit Double UP arrow
2    Select Config- Active- Edit
3    Hit RIGHT arrow ONCE
4    Select Chan- Display- Net
5    The N1-N2-N3 refer to Network Channel 1-3
6    If it shows D1 it refers to DTE channel 1
7    If it shows just a -, it is not programmed
8    If it shows PRT1, it is programmed as a Data Port
9    When finished hit double Arrow UP

To Assign Channels as Voice
1    Hit Double Arrow UP
2    Select Config- Active- Edit
3    Hit RIGHT arrow ONCE
4    Select DTE – Assign
5    It displays N1-N2- N3, select the corresponding ‘F’ key to assign
6    It now will show D* (* will be populated with the corresponding Channel #)
7    After assigning the voice channels, hit double UP arrow
8    If options were changed, you will be prompted to save ‘yes or no’
9    Select Active.

Print Friendly, PDF & Email

Discover more from IP Office Assistance

Subscribe to get the latest posts sent to your email.