Sagem 4450E - Manual (Page 164)

SAGEM 3P@C
3P@C Installation Manual
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1. The value of target noise margin (such as 12 db) can be
raised to improve the stability of the line connection.
2. In the practice, the house parallel exerts a great impact on
the connection rate, and this impact is especially obvious when
the subscriber cable exceeds 2.5km, so it is recommended to
reduce the application length of the house parallel.
1.1.1.61 Testing the ADSL Subscriber Line
There are certain requirements of the ADSL service commissioning on the subscriber lines:
„ No loading coils should be placed on line.
„ Better to use twisted pairs (paralleled iron wires and aluminium wires should not exceed 20 m)
„ No special requirements are imposed on the line shielding
„ In principle, no bridged tap should exist, even if so, its length should be less than 400m, and
the distance of it from the two ends should not be less than 400m, and the quantity of it not
exceed 2.
„ The DC loop resistance is required not more than 1.1 kΩ
„ The near-end protection ratio in terms of cable crosstalk should be more than 50db, while the
far-end protection ratio is equivalent to the former plus the line attenuation.
„ The normal line resistance is 100 Ω with the required error of not more than 10%.
„ The idle channel noise is required not more than -55dB, that is, the mean noise power
spectrum density is not more than -115dBm/Hz.
„ Within the range of ADSL service frequency band of 26K-1104KHz, the longitudinal
conversion loss is not less than 50dB, and in special cases, it is allowed to be more than
40dB.
Before the subscriber line is commissioned, the following checks should be made:
„ First, check the distance between subscribers and the 3P@C 4450E equipment, if it is above
2km, the materials for the house line should be strictly chosen, and the parallels of aluminium
or iron should not be used but the copper twisted pairs.
„ Check the proper contact of the house lines.
„ Check the proper insulation of the house lines.
„ Check the existence of radio sources around the house lines, including transmitting station
and arc welder.
„ Check how many devices are 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.
In addition, the subscriber line parameters should also be measured in respects of internal and external
measurements:
„ The internal measurement refers to the measurement on the distribution frame in the
distribution room.
„
The external measurement refers to the measurement of external lines.
Here, the internal measurement can be done simply by means of Modem or the handheld terminals which is
directly connected to 3P@C 4450E for test, and the status of lines can be judged by viewing the actual
connection parameters. Or the multimeter is used to measure the line parameters, including voltage,
capacitance and resistance. The detailed methods are as follows:
Voltage measurement
Disconnect the equipment from the tested lines, and select the DC voltage gear of the multimeter
to measure the voltage of –48V and BGND line from the external connecting terminals, the value
after measurement is the DC voltage of the subscriber line.
Select the AC gear of the multimeter to measure the AC voltage between Line A and B separately, the AC
voltage between Line A and the ground and the AC voltage between Line B and the ground.