Sagem 4450E - Manual (Page 177)

SAGEM 3P@C
3P@C Installation Manual
Page 12-20 Reproduction and communication in any form prohibited without the written permission of
SAGEM SA
1.1.1.70 Testing the VDSL Subscriber Line
There are certain requirements of the VDSL service commissioning on the subscriber lines:
„ The DC loop resistance is required not more than 300 Ω.
„ The nominal resistance (the AC resistance between twisted pairs) of lines is 100Ω, and the
error is required to be not more than 10%.
„ The lines cannot be attached with loading coils, and the practice of attaching the loading coils
on the subscriber line is rare in China.
„ Better to use twisted pairs (paralleled iron wires and aluminium wires should not exceed 20
m).
„ There are no special requirements for the shielding of lines; in principle, there should not exist
the bridged tap.
„ It is recommended to use in community, buildings or new branch offices but not in large
central offices, factories and roadside.
„ After the disconnection of Line A and B, the Line A-B, Line A/B-ground AC/DC voltage is
about 0V, and the result of below 1V is normal in the test by means of multimeter or 112 test
terminal.
„ The Line A-B insulation resistance and the Line A/B-ground should be more than 5M?.
„ The length of subscriber lines can be basically calculated according to the inter-line
capacitance of 50Nf/km, or the loop resistance. The DC resistance reference value of the
common lines is shown in the table below:
Table 12-11 DC resistance reference value of common lines
Diameter (mm) 0.32 0.4 0.5 0.6 0.8
DC resistance
(
Ω Ω Ω Ω/km)
236 148 95 65.8 36.6
Before the subscriber line is commissioned, check the quantity of devices being connected in series and parallel
on the house line, such as telephones, fax machines, charge registers, extensions of telephone, audio Modem,
and IP dialer, and make the detailed records for locating problems in maintenance.
1.1.1.71 Connection, Configuration and Commissioning of User End Devices
1) Connection splitter
The VDSL service is the traditional voice and data services run on a twisted pair, requiring the installation of
splitter at the user end to split voice from data. The correct installation of VDSL splitters is a key step in the
process of VDSL service commissioning.
The house line should be first connected into the Line port of the VDSL splitter, and all the voice devices should
be connected to the Phone port of the splitter and VDSL Modem to the Modem port.
Note
The practice of connecting to any voice devices before the Line port
of the splitter should be prohibited, or else, Modem cannot work
normally.
The method for correctly connecting the splitter is shown in the figure below: