Section 363-746-100
Revision 01
Page 2
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES
1.01
The PG-Flex FRL-746 Remote Terminal (RT)
Line Unit is the remote end of the PG-Flex
carrier system that uses two pairs of unconditioned
copper wire as a carrier for up to 32 independent
subscriber channels between a Central Office Terminal
(COT) and the RT. The FRL-746 RT Line Unit uses
PairGain’s High-bit-rate Digital Subscriber Line (HDSL)
technology to provide the equivalent of 2.048 Mbps
digital transmission rates, plus signaling over two copper
pairs without the need for repeaters, loop conditioning,
or pair selection.
1.02
The FRL-746 RT Line Unit resides in a PairGain
RT Enclosure; one FRL-746 RT Line Unit is
required for the system.
1.03
Revision History of this practice.
Revision 01 - May 13, 1996
a) Initial release.
1.04
FRL-746 RT Line Unit features:
•
Distributed subscriber carrier system
architecture
•
Proven PairGain HDSL (2B1Q) technology
operates on unconditioned copper pairs
−
Bridge taps permissible
−
No pair selection
−
No repeaters
2. APPLICATIONS
2.01
PG-Flex is a small capacity universal subscriber
carrier system supporting up to 24 subscriber
channels, including POTS and ISDN services. The
system is based on HDSL transmission technology and
the remote power is powered from the Central Office.
Using two 24 gauge (0.5 mm) unconditioned copper
pairs, the remote terminal may be located up to 10.7 kft
(3.3 km) from the Central Office terminal. Standard 19-
or 23-inch shelves contain multiple systems; circuit
cards may be hot-swapped without affecting other
systems installed in the shelf. POTS channel units use
64-kbps A-Law PCM encoding to allow Group 3
facsimile or high-speed modem operation on all
channels.
2.02
System Flex Configuration. A PG-Flex
system, shown in Figure 2 consists of:
•
Central
Office Terminal (COT). Two
complete systems may be installed in a 19-
inch COT Shelf and four complete systems
may be installed in a 23-inch COT Shelf.
Each system requires one COT Line Unit
and up to three (23-inch shelf) or six (19-
inch shelf) Channel Units. A common Alarm
Unit or Pair Gain Test Controller Interface
Unit in each shelf provides an interface for
maintenance alarm relays and metallic
access to the remote subscriber lines.
•
Remote Terminal (RT). The RT Enclosure
provides a weatherproof housing for the
PG-Flex remote electronics and subscriber
terminations. The enclosure accepts one
common RT Line Unit and up to four
Channel Units. The Remote Terminal
communicates with, and is line-powered
from, the COT over two pairs of 19- to 26-
gauge (0.9 mm to 0.4 mm) twisted-pair
telephone wire. Each pair carries both power
and HDSL signaling.
2.03
HDSL Transmission. PG-Flex utilizes HDSL
transmission technology between the COT and
RT and provides up to 32 DS0s, plus signaling, over two
copper pairs without the need for repeaters, loop
conditioning, or pair selection. Adaptive equalization,
scrambling, and a four-level 2B1Q line coding scheme
increase range and minimize crosstalk.
2.04
The line interface is a two-pair, 1110-kbps
full-duplex 2B1Q transmission format. The dual
HDSL lines provide 32 64-kbps channels with signaling,
and an embedded operations channel for management
control. The signal characteristics on the carrier pairs
comply with TR-NWT-001210, Generic Requirements for
High-bit-rate Digital Subscriber Line (HDSL) Systems.
2.05
For the system configuration depicted in Figure
2, the maximum distance between the COT and
the RT is 10.7 kft (3.3 km), assuming the HDSL lines are
24 gauge (0.5 mm). Table 1 shows the maximum
distance between the COT and RT for various gauge
wire. Due to the nature of HDSL transmission
technology, the HDSL lines do not require any special
conditioning and may include unterminated bridge taps,
but cannot include load coils.
2.06
Subscriber Drop Testing. For subscriber drop
testing from the Central Office, PG-Flex is able
to select and connect any subscriber drop to a metallic
test pair at the RT. PG-Flex extends this connection
back to the COT where technicians can switch it onto a
test access bus, or to the corresponding subscriber line
on the COT channel card.
2.07
Test access is achieved by p116 V on
the subscriber’s COT tip lead for 1.5 seconds,
then removing the +116 V. Depending on the
configuration of the PG-Flex system, the selected
subscriber drop (assuming a working metallic bypass
