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BT Versatility
Installation and Maintenance Manual
31
Cabling the unit
All Line and Extension circuit cabling is inserted from the top of the unit. There are breakouts as shown on
the top of the unit to facilitate routing of cables into the MDF area.
Connecting the extensions
It is recommended that all extensions be cabled with 2 pairs. The Featurephones use all four wires and
standard phones use the a,b pair only.
Do not exceed the following resistance or distance limits when connecting extensions to the System Unit.
(The distances listed assume 0.5mm-tinned copper conductor is used).
• 67 Ohms, or 400 metres, for system Featurephones.
• 336 Ohms, or 2 kilometres, for a standard telephone
• 336 Ohms, or 2 kilometres, for a standard telephone connected to the external extension on the
Options Module
The Extension cables must be of twisted-pair construction, using insulated tinned copper wires of nominal
0.5 mm
2
cross-sectional area. Category 5 cable must be used for all ISDN installations.
It is important that this size and type of wire is correct since incorrect types can result in unreliable
connections. Care should be taken to ensure that the cabling complies with all relevant cabling
requirements.
Run cable from each Extension location to the Main Equipment. Pass the cable through the cable entry
hole in the CCU or Expansion Module and terminate the Extension wiring at the appropriate connector in
accordance with the table below.
Cabling Break outs