Communication-Link Wire
BMTW-SVN01F-EN 61
When is the Link Repeater Required?
A link repeater is required when:
• The total wire length is greater than the maximum wire run length of
4,500 ft (1,400 m).
• More than 60 devices are connected to a link. This total does not
include the BCU, the link repeater, and the temporary use of the
Rover service tool on the same link.
• More than eight zone sensor communication stubs (maximum 50 ft)
are required on a Comm5 link (see “Zone Sensor Communication
Stubs” on page 144).
Link Repeater Limitations
The link repeater has several limitations:
• Only one link repeater can be used on a link.
• The use of a repeater doubles the maximum allowable wire length.
For example, when a repeater is used with a daisy chain configura-
tion, the total wire length can be 9,000 ft (2,800 m) (with half the wire
length on either side of the repeater).
• The link repeater is limited to 60 devices on either side of the link.
The total number of devices that can be attached to a repeater is 120.
• The link repeater requires a definite earth ground. The installer
should be aware of this before making any power connections.
Link Repeater Connections
Recommended shield connections are shown in Figure 29 on page 62.
Figure 30 on page 63 is an example of using a repeater to create an
extended daisy chain configuration.
Follow these guidelines when using a repeater:
• Read the Comm5 repeater installation, 3270 3285 information that
comes with the link repeater.
• For information about terminating daisy chain configurations, see
“Termination Resistance Placement for Comm5 Links” on page 59.
• For information about shielded cable connections, see “Recommended
Wiring Practices” on page 64.”
• Shield-drain wires entering the repeater should be connected to a ter-
minal marked with a capacitor symbol. The entering shield-drain
wire must be connected to earth ground at the BCU.
• Shield-drain wires leaving the repeater should be connected to the
repeater terminal marked with an earth ground symbol.
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