PairGain 150-1143-42, Руководство пользователя

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Product Overview 150-451-142-04, Revision 04
2 October 8, 1998 HDU-451 List 4B
In line with PairGain's continuing efforts to provide equipment that fully
complies with new industry standards, the List 4B doubler has been enhanced
with a special ground fault-detecting circuit described in Paragraph R7-1,
Section 7.2.1 of GR-1089-CORE, Issue 1, Revision 1, December, 1996.
When used with HiGain line units, ground faults occurring at any point along
any span on any wire are immediately detected. This condition shuts down the
HiGain circuit. The line unit will periodically try to apply power to the first
span to determine whether the fault condition is still present. As long as the
fault condition exists, the power cycling and ground fault protection
continues.
Circuits containing both the new List B and older doublers also support this
new ground fault detecting feature, provided the doubler nearest the HLU is
a List B unit. The presence of this new circuit causes the HDSL
span-powering voltage levels to be shifted up to 100 volts more positive than
what they are in non-List B doubler circuits. The actual shift depends on loop
length, number of doublers, HRU powering option, and the setting of the
HLU Bipolar/Unipolar Switch. The List B doublers are backward-compatible
with all versions of HiGain line units.
A
PPLICATIONS
The primary application of the HDU-451 HiGain Doubler is to extend the
delivery of T1 High Capacity Digital Service (HCDS) to customers over
metallic cable pairs, up to 24,000 or 36,000 feet (24 AWG). A doubler
application is shown in
Figure 1 on page 3 . A maximum of two HDU-451
units can be used in tandem on the same circuit.
Table 1 on page 3 provides a guide for the loss of various cable gauges at
196 kHz and 135 ohms. The table applies to the HDSL cable pairs between
the HLU and the HDU-451 as well as between the HDU-451 and a second
HDU-451 or the HRU-412. Add 3 dB for each bridged tap and 1 dB for each
cable gauge change.
The operation of the ground fault circuit requires that the
doubler enclosure be connected to earth ground.