Section 363-712-100
Revision 02
Page 2
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES
1.01
The PG-Flex FLL-712 Central Office Terminal
(COT) Line Unit is the Central Office end of the PG-Flex
subscriber carrier system that uses two pairs of
unconditioned copper wire as a carrier for up to 24
subscriber channels between a COT and a Remote
Terminal (RT). The List 1 supports 4Tel compatible Loop
Test Systems. The List 2 provides both 4Tel and
MLT/PGTC compatibility. The FLL-712 COT 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.
1.02
The FLL-712 COT Line Unit resides in a
PairGain COT Shelf; one FLL-712 COT Line Unit is
required for each system.
1.03
Revision History of this practice:
Revision 02—December 18, 1996
a) Added List 2.
1.04
FLL-712 COT 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 channels including both
POTS and ISDN services. The system is based on HDSL
transmission technology using two 24 gauge unconditioned
copper pairs. The remote terminal may be located up to
12.3 kft from the central office terminal and is powered
from the central office. In the central office, multiple
systems may be mounted in either 19 or 23-inch shelves.
Circuit cards may be hot-swapped without affecting other
systems in the same shelf. The PCM encoding scheme
used in the POTS channel units allows high speed modem
and group 3 facsimile 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.
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
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.
