PairGain PG-Flex FRC-751 User manual

PAIRGAIN TECHNOLOGIES Section 363-751-100
Technical Practice Revision 01
Engineering - PLANT Series February 12, 1996
Page 1
PAIRGAIN TECHNOLOGIES PG-FLEX™RT CHANNEL UNIT
MODEL FRC-751 List 1
PairGain #150-1351-01
CLEI Code: VARHCD0CAA
CONTENTS PAGE
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES 2
2. APPLICATIONS 2
3. SPECIFICATIONS 3
4. CERTIFICATION 4
5. WARRANTY 4
B. FUNCTIONAL DESCRIPTION
6. OPERATIONAL
CAPABILITIES 4
7. FRONT PANEL 5
C. INSTALLATION AND TEST
8. UNPACKING 5
9. TURN-UP AND TESTING 5
10. TROUBLESHOOTING 5
CAUTION
This product incorporates static sensitive components.
Proper electrostatic discharge procedures must be
followed.
Figure 1. FRC-751 Channel Unit, List 1, Front Panel. The
PairGain FRC-751 provides four POTS interfaces between a PG-
Flex Remote Terminal and the subscriber.

Section 363-751-100
Revision 01
Page 2
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES
1.01 The FRC-751 Channel Unit provides four POTS
interfaces between a PG-Flex Remote Terminal
(RT) and subscribers. The FRC-751 Channel Unit uses µ-
Law PCM encoding. The unit includes status LEDs for each
line indicating idle, ringing and off-hook conditions, as well
as an LED indicating a fault condition on the Channel Unit.
The unit provides metallic test access to the subscriber line
for connecting through an optional metallic bypass pair.
1.02 Revision History of this practice.
Revision 01 - February 12, 1996
a) Initial release.
1.03 Features of the PG-Flex FRC-751 RT Channel Unit:
• Four POTS subscriber interfaces
• 64 kbps µ-Law PCM encoding
• Front panel ACTIVE LEDs indicate idle, ringing,
and off-hook conditions for each channel
• Front panel FAULT LED indicator simplifies
troubleshooting
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 minimize
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 depicted 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 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 placing +116 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.
2.08 The test connection will be dropped when -116V is
applied to the subscriber’s COT tip for 1.5 seconds,
then removing the -116 V.
2.09 Test access may also be activated through the RS-
232 Maintenance Port located on the front of the
COT and RT Line Units, using an ASCII terminal.

Section 363-751-100
Revision 01
Page 3
Figure 2. Typical PG-Flex Configuration.
TABLE 1. PG-FLEX DISTANCES
Loop Length
Wire Gauge 12/24 Channel System Resistance
26 AWG (0.4 mm) 9.0 kft (2.8 km) 750
W
24 AWG (0.5 mm) 12.3 kft (3.8 km) 638
W
22 AWG (0.6 mm) 16.1 kft (5.0 km) 521
W
19 AWG (0.9 mm) 22.8 kft (7.0 km) 367
W
3. SPECIFICATIONS
Analog Impedance
600 ohms
DC Loop Current
Greater than 23 mA into off-hook dc resistance
Ringer Output Drive
15 REN maximum per RT, 5 REN maximum
per channel
RT DC Supervisory Range
960 ohms. Maximum cable loop resistance,
minus 430 ohms for handset, is 530 ohms
RT Idle State Loop Voltage (On-Hook)
Greater than 40 V dc. Ring is negative with
respect to Tip
RT Loop Closure (Off-Hook) Detection
Less than 960 ohms between Tip and Ring
RT On-Hook Detection
Greater than 10 kohms
Operating Temperature & Humidity
-40° to +65° Celsius, 5% to 95% non-
condensing
Operating Elevation
200 feet (60 m) below sea level to 13,000 feet
(4,000 m) above sea level.
Dimensions
Height: 12.00” (30.5 cm)
Width: 1.00” (2.5 cm)
Depth: 4.50” (11.4 cm)
Weight
0.6 lb. (0.3 kg)

Section 363-751-100
Revision 01
Page 4
4. CERTIFICATION
4.01 FCC Compliance. The FRC-751 Channel Unit
complies with the limits for Class A digital devices
pursuant to Part 15 of the FCC rules. These limits are
designed to provide reasonable protection against harmful
interference when the equipment is operated in a commercial
environment. This equipment generates, uses and can radiate
radio frequency energy and, if not installed and used in
accordance with the instruction manual, may cause harmful
interference to radio communications. Operation of this
equipment in a residential area is likely to cause harmful
interference in which case the user will be required to correct
the interference at his own expense.
4.02 Refer to the installation section of the appropriate
instruction manual for the unit you are installing to
get information on:
• Cabling
• Proper connections
• Grounding
• Line vs. local power
4.03 All wiring external to the product(s) should follow
the provisions of the current edition of the National
Electrical Code.
5. WARRANTY
5.01 PairGain Technologies warrants this product to be
free of defects and to be fully functional for a period
of 36 months from the date of original shipment, given
proper customer installation and regular maintenance.
PairGain will repair or replace any unit without cost during
this period if the unit is found to be defective for any reason
other than abuse or improper use or installation.
5.02 This module should not be field repaired. If it fails,
replace it with another unit and return the faulty unit
to PairGain for repair. Any modifications of the unit by
anyone other than an authorized PairGain representative will
void the warranty.
5.03 If a unit needs repair, call PairGain for a Return
Material Authorization (RMA) number and return
the defective unit, freight prepaid, along with a brief
description of the problem, to:
PairGain Technologies, Inc.
14402 Franklin Avenue
Tustin, CA 92680
ATTN: Repair and Return Dept.
[phone]
5.04 PairGain will continue to repair faulty modules
beyond the warranty program at a nominal charge.
Contact your PairGain sales representative for details and
pricing.
B. FUNCTIONAL DESCRIPTION
6. OPERATIONAL CAPABILITIES
6.01 Each FRC-751 RT Channel Unit provides four
POTS interfaces between the RT and subscribers,
and performs the following functions:
• 64 kbps µ-Law PCM encoding
• Applies ringing voltage
• Generates forward disconnect
• Detects an off-hook or ring-trip condition
• Connects a subscriber loop to a metallic test pair
• Protects against secondary surges and power line
cross
6.02 A block diagram of the FRC-751 is shown in
Figure 3.
Figure 3. FRC-751 Block Diagram.

Section 363-751-100
Revision 01
Page 5
7. FRONT PANEL
7.01 The front panel of the FLC-751 Channel Unit
contains the following indicators (see Figure 1):
• ACTIVE 1, 2, 3, 4 LED Indicators
Green—the channel is off-hook.
Flashing Green—the channel is ringing (the LED
will track the ringing) or the line has been switched
to the test pair.
Off—the channel is on-hook.
• FAULT LED Indicator
Red—a fault has been detected on the unit.
Off—no faults are detected on the unit.
C. INSTALLATION AND TEST
8. UNPACKING
8.01 Upon receipt of the equipment, proceed as follows:
1. Unpack each container and visually inspect
it for signs of damage. If the equipment has
been damaged in transit, immediately report the
extent of damage to the transportation company
and to PairGain. Order replacement equipment
if necessary.
2. Check the contents versus the packing list to
ensure complete and accurate shipment. If the
shipment is short or irregular, contact PairGain
as described in Section 5. If you must store the
equipment for a prolonged period, store the
equipment in its original container.
9. TURN-UP AND TESTING
9.01 Table 2 provides step-by-step turn-up and test
procedures for the FRC-751 Channel Unit.
10. TROUBLESHOOTING
10.01 Table 3 provides troubleshooting procedures based
on indications displayed by the front panel
indicators of FRC-751 Channel Unit.
TABLE 2. FRC-751 RT CHANNEL UNIT TURN-UP AND TESTING
CAUTION
Observe normal electrostatic discharge precautions when handling electronic equipment. Do not hold electronic plug-ins
by their edges. Take care not to touch components or circuitry.
Step Operation Action Observe
1 Install RT
Channel
Units
a. Insert each FRC-
751 Channel Unit
into the FRE-765 RT
Enclosure.
All LEDs on the Channel Unit will turn on for approximately 2 seconds, then scan
from top to bottom, then turn off.
b. After the system
has powered up,
established HDSL
synchronized
communications, and
no calls are in
progress, observe the
Channel Unit front
panel indicators.
ACTIVE 1 off
ACTIVE 2 off
ACTIVE 3 off
ACTIVE 4 off
FAULT off
2 Test
Subscriber
Circuits
a. Test each
subscriber circuit by
placing and receiving
calls.
ACTIVE 1 through 4 LEDs track call as described in paragraph 7.01.

Section 363-751-100
Revision 01
Page 6
TABLE 3. FRC-751 RT CHANNEL UNIT TROUBLESHOOTING
Indication Problem Action
FAULT
LED on The processor in the RT Line Unit
has stopped.
Remove and replace the RT Line Unit. If the system does not restart, replace the RT Line Unit.
Troubleshooting based on customer-originated trouble reports
No
Dialtone,
Can’t Dial
Short circuit,
faulty COT, or
faulty RT
Channel Unit.
1. Lift the subscriber pair at the RT. If dialtone is present at the RT and calls can be placed,
check for shorts toward the subscriber or on the customer’s premises.
2. If you cannot hear a dialtone and/or cannot make calls at the RT with the subscriber drop
lifted, lift the jumper in the CO between the CO switch and the COT. If you hear a dialtone
and/or can make calls at the switch, replace the COT Channel Unit and/or RT Channel Unit.
Otherwise, the problem is in the CO switch.
Phone
Doesn’t
Ring
High-resistance
short on
subscriber drop,
faulty RT
Channel Unit, or
faulty RT Line
Unit.
1. Check for ringing at the RT. If ringing isn’t present on the line under test, try ringing
another line terminated on the same RT Channel Unit. If ringing is present on other lines,
check for high resistance shorts on the subscriber drop.
2. If ringing isn’t present on a circuit terminated on the same RT Channel Unit, try ringing a
line terminated on another RT Channel Unit. If the line rings, replace the RT Channel Unit. If
the line doesn’t ring, replace the RT Line Unit.
Phone
Doesn’t Stop
Ringing
Faulty subscriber
station instrument,
faulty RT Channel
Unit, or loop length
too long.
Phone stops ringing when using a butt-in at subscriber location:
Subscriber’s station instrument’s internal resistance is too high. Replace instrument according
to local policies.
If phone doesn’t stop ringing when using a butt-in at the subscriber location, re-test at the RT:
If phone still doesn’t stop ringing, replace the RT Channel Unit.
Otherwise, loop length between RT and subscriber is too long.
Can’t Hear,
Can’t Be
Heard
Subscriber
problem, faulty
COT Channel Unit,
or faulty RT
Channel Unit.
1. Lift the subscriber drop at the RT. If audible level is acceptable, there is a problem toward
the subscriber.
2. If audible level is too low at the RT with the subscriber drop lifted, lift the jumper in the
CO between the CO switch and the COT. If audible level is acceptable, replace the COT
Channel Unit and/or RT Channel Unit. Otherwise, the problem is in the CO switch.
Copyright © 1996, PairGain Technologies, Inc. PairGain is a registered trademark, CopperOptics and HiGain are trademarks of
PairGain Technologies, Inc.