Section 363-742-102
Revision 01
Page 2
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES
1.01
The PG-Flex FRL-742 Remote Terminal (RT) Line
Unit is the remote end of the PG-Flex subscriber carrier
system that uses two pairs of unconditioned copper wire as a
carrier for up to 24 independent subscriber channels between
a Central Office Terminal (COT) and the RT. The FRL-742
RT Line Unit uses PairGain’s High-bit-rate Digital
Subscriber Line (HDSL) technology to provide the equivalent
of 1.544 Mbps digital transmission rates, plus signaling over
two copper pairs without the need for repeaters, loop
conditioning, or pair selection. The List 1 supports 4Tel
compatibility loop test systems. The List 2 provides both
4Tel and MLT/PGTC compatibility.
1.02
The FRL-742 RT Line Unit resides in a PairGain RT
Enclosure; one FRL-742 RT Line Unit is required for the
system.
1.03
Revision History of this practice.
Revision 02—December 18, 1996
a) Added List 2.
1.04
FRL-742 RT Line Unit features:
•
Distributed subscriber carrier system architecture
•
Proven PairGain HDSL (2B1Q) technology
operates on unconditioned copper pairs
Bridge Taps
No Pair Selection
No Repeaters
•
4Tel Loop Test System compatibility (List 1, 2)
•
MLT/PGTC Loop Test System compatibility
(List 2)
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
unconditioned copper pairs, the remote terminal may be
located up to 12.3 kft 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
µ
-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 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 24 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 minimizes
crosstalk.
2.04
The line interface is a two-pair, 784-kbps full-duplex
2B1Q transmission format. The dual HDSL lines provide 24
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 shown in Figure 2,
the maximum distance between the COT and the RT is 12.3
kft (3.8 km), assuming the HDSL lines are 24 gauge. 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 it
can be switched onto the test access bus, or to the
corresponding subscriber line on the COT channel card.
2.07
Test access may be 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 pair) will be connected to either the
corresponding COT subscriber line or to the test access bus.
