Section 150-231-164
Revision 04
Page 2
A. GENERAL
1. INTRODUCTION
1.01
The PairGain HiGain Line Unit Model HLU-231
Issue 1, List 6D (Figure 1), is the Central Office
(CO) side of a repeater-less T1 transmission system.
When used in conjunction with a HiGain Remote Unit
Model HRU-412, the system provides 1.544 Mbps
transmission on two unconditioned copper pairs over the
full Carrier Serving Area (CSA) range. The “D”
designation in the list number indicates that this line unit
can be used in applications with or without the HiGain
Doubler Unit (HDU-451). The CSA includes loops up to
12000 feet of AWG 24 or 9000 feet of AWG 26 wire,
including bridged taps. The HiGain system uses HDSL
(High-bit-rate Digital Subscriber Line) transmission
technology as recommended by Bellcore TA-TSY-
001210. The HiGain system complies with TR-TSY-
000063 (Network Equipment Building System (NEBS)
Generic Equipment requirements) and TR-TSY-000499
(Transport System Generic Requirements - TSGR)
common requirements.
1.02
Revision History of this practice.
Revision 04—March 30, 1995
a) Modified the data in Table 9.
b) Changed the different settings of the DS1
line code to AMI from AUTO.
c)
Changes initiated by software Version 1.4.
1.03
HLU-231, List 6D features:
•
Selectable DSX-1 Pre-equalizer
•
-130 V to -210 V self-adjusting line voltage
for HRU-412 and HDU-451 applications
•
Front Panel HDSL S/N Margin Display
•
Selectable Loopback activation codes
•
RS-232 maintenance port
•
Front-panel user option setup
•
Front Panel DS1 splitting & bridging access
•
Lightning and power cross protection on
HDSL interfaces
•
784 kbps full-duplex 2B1Q HDSL
Transmission on two pairs
•
Front panel status indicating LED
•
Automatic front-panel display blanking
•
Margin threshold alarm
•
HAIS & SAIS options
•
Easy default setting of user options
•
New T1 transceiver chip
•
Circuit ID option
2. APPLICATIONS
2.01
The HiGain system provides a cost-effective,
easy to deploy method for delivering T1 High
Capacity Digital Service (HCDS) over metallic pairs.
The fiber-like quality service is deployed over two
unconditioned, non-loaded copper pairs. Conventional
in-line T1 repeaters are not required. Cable pair
conditioning, pair separation and bridged tap removal,
are not required.
2.02
The general guidelines require that each loop
have less than 35 dB of loss at 196 kHz, with
135 ohms driving and terminating impedances. The
HiGain system operates with any number of other T1,
POTS, Digital Data Service (DDS) or other HiGain
systems sharing the same cable binder group. HiGain
systems can be used with customers requiring DS1
service on a temporary or permanent basis. The HiGain
system also provides a means of quickly deploying
service in advance of fiber-optic transmission systems.
With the HiGain system, service can be provided within
hours. Fiber optic systems can be installed at a leisurely
pace and cut-over from the installed HiGain system
when convenient to do so. The installed HiGain system
can then be easily removed and utilized elsewhere.
3. FUNCTIONAL OPERATION
3.01
The HiGain system uses PairGain 2-Bit
1-Quartenary (2B1Q) HDSL transceiver systems
to establish two full-duplex 784 kbps data channels
between the HLU-231 List 6D and a remotely mounted
HRU-412 HiGain Remote Unit. This provides a total
capacity of 1.568 Mbps between the two units.
3.02
A block diagram of the HLU-231 List 6D is
shown in Figure 2. The HiGain HLU-231 List 6D
receives a 1.544 Mbps DS1 data stream from the DSX-1
digital cross connect interface. The HLU-231 List 6D
contains a DS1 frame synchronizer controlled by an 8-bit
microprocessor that determines the type of framing on
the DS1 stream and synchronizes to it. The HLU-231
List 6D recognizes Super Frame (SF) (including D4) or
Extended Super Frame (ESF) framing. When the data
is unframed, the HLU-231 List 6D arbitrarily defines a
frame bit.
3.03
The HLU-231 List 6D contains a demultiplexer
that generates two parallel 784 kbps data
streams. The data streams contain HDSL frames that
are nominally 4704 bits (6 milliseconds) in length. The
HDSL frames contain a 14 bit Frame Sync Word (FSW),
6 bit Cyclic Redundancy Check (CRC), 21 bit operations
channel and DS1 payload. The DS1 stream is
separated into two parallel streams that comprise the
