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SCP-FLL814-012-04H
HDSL T
RANSMISSION
The system uses HDSL 2B1Q technology to transport 24 DS0s plus signaling over two copper pairs. The HDSL
circuits can be used without repeaters or loop conditioning. Adaptive equalization, scrambling, and a four-level
2B1Q line coding scheme are used to maximize distance and minimize crosstalk.
Table 1
shows the maximum distance between the COT and RT for various wire gauges and with up to two doublers
in the circuit. These distances are shown for a cable temperature of 68º F (20º C). As the temperature of the cable
increases, the distance decreases.
Gauge Wire
26 AWG (0.4 mm)
9.0 kft (2.8 km)
24 AWG (0.5 mm)
12.3 kft (3.8 km)
22 AWG (0.6 mm)
16.1 kft (5.0 km)
19 AWG (0.9 mm)
22.8 kft (7.0 km)
When the RT is powered from the COT, two auxillary power pairs are required between the COT and RT for each
doubler installed in the HDSL circuit. The power pairs should meet the same criteria as the HDSL pairs. Refer to the
COT Shelf and RT Enclosure technical practices for additional information on the power pairs. The RT can also be
locally powered to eliminate the need for auxiliary power pairs.
S
C
EALING
URRENT
The FLL-814 provides line powering voltage even if the RT Line Unit is locally powered. In this configuration, the
locally powered RT Line Unit draws no current on the HDSL pairs. In order to allow the operating company to "wet"
the HDSL lines, the locally powered RTLU provides a provisionable sealing current load circuit. This feature is
provisionable as ENABLED or DISABLED. The default is DISABLED. Refer to CONFIG — System Options section
for a description of provisioning the sealing current feature.
DISABLED
If a single span system is used, no current flows in the span between the RT and the CO. If doublers are used, no
current flows in the span between the last doubler and the RT. Current does flow in the spans between the CO and
doublers since the doublers are still line powered.
ENABLED
The Sealing Current load is automatically applied for a period of 15-20 seconds, once every 24 hours at the system
clock time of 00:05. A minimum of 20 mA is drawn through each conductor of HDSL A and B during the time the
sealing current feature is active. The current flow is ramped at a rate less than 20 mA/second to meet industry
standard requirements for pulsed sealing current.
4
Table 1. HDSL Distances
HDSL Distance (6 dB Margin / 35 dB Loss / 68
No Doubler
1 Doubler
18.0 kft (5.6 km)
24.6 kft (7.6 km)
32.2 kft (10.0 km)
45.6 kft (14.0 km)
F)
°
2 Doublers
27.0 kft (8.4 km)
6.3 kft (1.9 km)
36.9 kft (11.4 km)
10.2 kft (3.1 km)
48.3 kft (15.0 km)
16.3 kft (5.0 km)
67.4 kft (21.0 km)
32.9 kft (10.0 km)
ADC Telecommunications, Inc.
April 22, 2003
Analog Drop
(530 Ω)
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