Appendix B: I/O, maintenance, and extender cable description Page 863 of 910
IP Line Description, Installation and Maintenance

Prevent ground loops on connection to external customer

LAN equipment

The shielded RJ-45 coupler is the connection point for the customer’s
shielded CAT5 LAN cable to the hub, switch, or router supporting the TLAN
and ELAN subnets. Use shielded CAT5 RJ-45 cable to connect to the
customer’s TLAN/ELAN equipment. Follow the steps in Procedure 124 to
prevent ground loops when connecting to external customer LAN equipment.
Follow the steps in Procedure 124 to prevent ground loops.
Procedure 124
Preventing ground loops
1Connect the customer-provided shielded CAT5 LAN cable to the external
LAN equipment. Ensure that the external LAN equipment is powered-up.
2Use an ohmmeter to measure resistance to ground between the free end
of the shielded RJ-45 cable and the building ground.
The ohmmeter must measure Open to ground before plugging it into the
shielded RJ-45 coupler on the end of the NTMF94EA.
If the ohmmeter does not measure Open, install the unshielded RJ-45
coupler (provided) on the end of the NTMF94EA to prevent ground loops
to external LAN equipment.
End of Procedure
WARNING
The serial maintenance ports on the faceplate connector
and the DB-9 female connector of the NTMF9DA cable
assembly are identical. Do not connect a serial device to
both access points simultaneously. This results in
incorrect and unpredictable operation of the Voice
Gateway Media Card.