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E1VI PRI signal common problem with some PBX

Publication Date:  2012-07-27 Views:  303 Downloads:  0
Issue Description
PBX user should first dial 9 to access one line from the 30 lines of the E1 trunk , he will hear a dial tone ,after that he should dial the FXS destination number , but the actual problem is that when the PBX user dial 9 he heared a fast busy tone not a dial tone , also when the FXS user try to call any PBX user , after he dial the number he heared a fast busy tone so that is mean there is a problem of the E1 trunk line
Alarm Information
when open the debug switch for ISDN q921 and q931 , i found that the layer 2 not up and the (tei) is assigned for second and after that not assigned (assigned and not assigned , ), and in PBX there was alarm regarding the E1port means that (Multiframe Error)
Handling Process
First i checked the configuration for the router and Contrroler e1 : 1- make check for the number of voice channels which are members of the PRI Group and no problem 2- check the clocking of the system between router and PBX and no problem 3-chek the framing, and no problem 4 - we test the PBX and connect the E1 of PBX to the E1 comming from Telecom Company(ISDN/PRI) and the call suceed , so it is clear that the problem is the compatability between router and PBX. after i cheked the PBX manual , i found that there is two Modes regarding the E1 (NT and TEI ) which mean respectivle (Network side and Subscriber side). and the default for PBX is Subscriber side , and also our quidway router suport only subscriber side for PRI signaling , so this was the problem , because when connecting the PRI one side must a subscriber side and the other side must be Network Side , after i change the E1 working mode for the PBX to Network side(NT) , the test is succeeded and no problem with the implementation.
Root Cause
When connecting the E1VI port of router using PRI signaling to any PBX , be sure thet the E1 port of PBX is configured as network side. not Subscriber side .
During router test to implement the VOIP application,we have one router with one FXS port connected to telephone set and E1VI port connected to LG PBX . it is required to make the users who connected to PBX ,call the user who connected to FXS port through E1VI. , the E1 signaling type was PRI because LG GDK-100 support only PRI signaling .