103
Addressable Loop Interference on Phone Handset Lines
13.4 Use Shielded Wiring
• Use 18 gauge shielded twisted pair cables for the connections between TNC-5000
telephone bus terminals, and for the connections between the addressable modules.
• Use shielded cables for the connections between the addressable modules and the
telephone handsets, if possible.
To connect the TNC-5000 telephone bus terminals with shielded wiring
1. Wire the TNC-5000 boards as explained in LT-894SEC MMX Installation and Operation
Manual.
Each board has 2 buses: 1 IN bus and 1 OUT bus.
Each bus has 3 terminals: positive (+), negative (-), and shield (S).
2. Connect the positive, negative, and shield wires of one end of the cable to the Tel. Bus
OUT of the previous board.
3. Connect the positive, negative, and shield wires of the other end of the cable to the Tel.
Bus IN of the next board.
Terminate both ends of the shield.
Figure 63 Wiring of the TNC-5000 boards
To connect the M500 addressable modules with shielded wiring
1. Wire the addressable modules as explained in LT-894SEC MMX Installation and
Operation Manual.
2. Connect the shields to each other with twist-on wire connectors (marettes).
Terminate only one end of the shield.
• For class A wiring, leave the shield unconnected at the end of the loop (where the
wires return to the module).
Tel. Bus
Out
Tel. Bus
In
TNC-5000
+ - S
Tel. Bus
Out
Tel. Bus
In
TNC-5000
Tel. Bus
Out
Tel. Bus
In
TNC-5000
+ - S
+ - S
+ - S
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