Section 150-388-124
Revision 01
Page 10
6. HDSL LINE VOLTAGE OPTION
6.01
The symmetry of the HDSL line powering voltage
can be set by the S2 switch, located on the printed
circuit board, as shown in Figure 5.
6.02
The factory default setting is unipolar (-). It sets
the HDSL line voltage to 0 V on loop 2 and to
either -130 V (for non-doubler applications) or -200 V (for
doubler applications) on loop 1. This setting keeps the
HDSL cable pair voltage at or below ground potential,
thereby avoiding corrosion problems caused by cable
voltages more positive than ground.
6.03
The bipolar selection sets the HDSL line voltage to
+65 V on loop 2 and -65 V on loop 1, for non-
doubler applications. Doubler applications will have +100
V on loop 2 and -100 V on loop 1. This setting reduces the
maximum ground referenced voltage to 100 V, but applies
positive voltage to the cable pairs, which could accelerate
corrosion on the cable pairs.
6.04
The line voltage power supply, used for both
options, is ground referenced, but also ground
isolated by 200 kohms. This ground isolation reduces
problems due to induced noise currents and large surge
voltages, which are ground referenced. It also reduces
ground fault currents, which improves the product’s safety.
The safety issue thus depends solely on the differential
voltage across loop 1 and loop 2, and is independent of S2’s
setting.
7. INSTALLATION
7.01
Upon receipt of the equipment, visually inspect it
for signs of damage. If the equipment has been
damaged in transit, immediately report the extent of damage
to the transportation company and to PairGain
Technologies.
7.02
The HLU-388 mounts in the group of both wire-
wrapped and connectorized shelves listed in
Section A Paragraph 1.02. The HLU-388 slot pins are
shown in Figure 4.
Figure 5. HDSL Line Voltage Switch S2
