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Wire Mapper Pro Model CA7028
4.11 Cable Length Measurement
Structured Cable Tester
WIRE MAPPER PRO
MODEL CA7028
SERVICE / Vp
MAP /
LENGTH / Vp
The remote unit does not need to be attached for this
test to be performed. Although it does not matter if it
is attached, any terminators on ISDN wiring or sockets
should be switched out of the circuit or disconnected.
Attach the main unit to one end of the cable and press the
LENGTH / Vp
button.
The length of all four pairs in the cable are measured, and the results dis-
played simultaneously, as shown below.
Pr.
4-5
64ft
Pr.
1-2
64ft
Pr.
3-6
-----
Pr.
7-8
64ft
TIA568 UTP Vp=71%
In this example, the length of pair 3 - 6 is missing, as there is a fault on the
pair which is preventing the TDR circuit from measuring the length.
Length will be displayed in the selected units, either meters or feet, and
the Vp and cable testing standard will also be displayed. Length measure-
ment accuracy depends on the correct setting of the Vp (Velocity of Propa-
gation) for the cable under test.
If the Vp is not known for a particular cable, then a known length of that
cable (at least 60ft or 20m long) may be connected to the instrument and
the Vp adjusted until the correct length reading is obtained (see § 4.3).
