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Chapter 7: Troubleshooting
directory number(s) provided with the ISDN line. Calling a good ISDN
line with nothing connected usually results in a ring or fast busy tone. If
the call is completed or a not-in-service intercept is received, then there is
probably something wrong with the translation of the ISDN line. Contact
the phone service provider for help.
3.
If the ISU 512 continues to read DOWN, there is a physical problem with
the ISDN line (probably Layer 1 setup). The problem is one or more of the
following:
•
The ISU 512 software setup
•
The ISU 512 hardware
•
CPE wiring
•
Wiring from the telephone service provider
•
Hardware of the telephone service provider
•
Software setup of the telephone service provider
To isolate the problem, perform the following procedure:
A. Ensure the ISDN line is plugged into the correct IFC connector on the
back of the ISU 512.
B.
Ensure the ISU 512 is configured for Dial Line service.
CONFIG, Netw. options, and Dial Line should be selected from
the menu.
C. Connect another piece of functioning ISDN equipment to the
ISDN line.
D. Contact the service provider and ensure you have an ISDN Basic
Rate U-Interface with 2B1Q line coding (wrong options are an
S or T interface or AMI line coding). For the ISU 512 (ST), the
S or T interface option would be correct.
E.
Ensure the ISDN phone lines are connected to the actual ISDN
telephone line (Basic Rate interface) provided by the telephone
company. Ensure the ISDN line is not connected through
another piece of equipment in a wiring closet.
62
ISU 512 User Manual
61202.086L1-1
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