PairGain PG-Flex FRC-754 L4 User manual

PG-FLEX 8 CHANNEL REMOTE TERMINAL
LOOP START/GROUND START POTS UNIT
PAIRGAIN TECHNOLOGIES, INC.
ENGINEERING SERVICES TECHNICAL PRACTICE
™363-754-104-01J¨
SECTION 363-754-104-01
Model List Number Part Number
FRC-754 4 150-1354-04

363-754-104-01, Revision 01
ii June 22, 1998 FRC-754 List 4
Revision History of This Practice
©Copyright 1998 PairGain Technologies, Inc.
PairGain is a registered trademark, and PG-Flex is a trademark of PairGain Technologies, Inc.
Information contained in this document is company private to PairGainTechnologies, Inc.,and shallnot be modified, used, copied,
reproduced or disclosed in whole or in part without the written consent of PairGain.
Other product names mentioned in this practice are used for identification purposes only and may be trademarks or registered
trademarks of their respective companies.
Revision Release Date Revisions Made
01 June 22, 1998 Initial Release

363-754-104-01, Revision 01 Using This Technical Practice
FRC-754 List 4 June 22, 1998 iii
USING THIS TECHNICAL PRACTICE
Two types of messages, identified by icons, appear in the text.
Notes contain information about special circumstances.
Cautions indicate the possibility of equipment damage or the possibility of personal injury.

Table of Contents 363-754-104-01, Revision 01
iv June 22, 1998 PG-Flex FRC-754 List 4
TABLE OF CONTENTS
Product Overview_____________________________________________________________________ 1
Description and Features................................................................................................................... 1
Front Panel......................................................................................................................................... 2
Specifications .................................................................................................................................... 3
Operational Capabilities.................................................................................................................... 4
Circuit Operation............................................................................................................................... 4
Loop Start Operation........................................................................................................... 4
Ground Start Operation....................................................................................................... 6
CLASS Features..................................................................................................................7
Forward Disconnect............................................................................................................ 7
Installation and Test___________________________________________________________________ 8
Unpacking.......................................................................................................................................... 8
Installing............................................................................................................................................ 8
Provisioning....................................................................................................................................... 8
Verify Installation.............................................................................................................................. 9
Troubleshooting............................................................................................................................... 10
Product Support _____________________________________________________________________ 11
Technical Support............................................................................................................................ 11
Warranty.......................................................................................................................................... 11
FCC Compliance............................................................................................................................. 12
Modifications................................................................................................................................... 12
Abbreviations _______________________________________________________________________ 12

363-754-104-01, Revision 01 Product Overview
PG-Flex FRC-754 List 4 June 22, 1998 1
PRODUCT OVERVIEW
This section provides a product description, and defines the features and specifications for the PairGain®
PG-Flex™ FRC-754 List 4 Remote Terminal (RT) Channel Unit.
Description and Features
The FRC-754 List 4 channel unit provides eight loop start or ground start Plain Old Telephone Service (POTS)
interfaces between a PG-Flex RT andsubscribers. The FRC-754 List 4 uses A-Law pulse code modulation (PCM)
encoding. For subscriber circuit testing, the FRC-754 List 4 provides metallic access to the subscriber line
connection through an optional metallic bypass pair.
Features of the PG-Flex FRC-754 List 4 channel unit are:
•eight loop start or ground start POTS subscriber interfaces
•64 kbps A-Law PCM encoding
•meter tones (12 kHz, 16 kHz)
•front panel ACTIVE LEDs indicate on-hook (idle), ringing, metallic access, and off-hook condition for each
channel
•front panel FAULT LED indicator simplifies troubleshooting
•Pair Gain Test Controller (PGTC) compatibility
•Custom Local Area Signaling Services (CLASS) support (such as, caller ID)
•line-side answer supervision support (reverse battery)
•forward disconnect
•distinctive ringing
•application of ringing voltage
•detection of loop off-hook, ground start seizure, and Ring-Trip conditions

Product Overview 363-754-104-01, Revision 01
2 June 22, 1998 PG-Flex FRC-754 List 4
Front Panel
The FRC-754 List 4 front panel (Figure 1) includes green status LEDs for each line indicating on-hook (idle),
ringing, and off-hook conditions, as well as a red LED indicating a fault condition on the channel unit. Table 1
lists the FRC-754 List 4 front panel LED states and functions, and describes the labels.
Figure 1. FRC-754 List 4 Front Panel
Table 1. FRC-754 List 4 Front Panel LEDs and Labels
LED and Labels Function
Solid green: Channel is off hook.
ACTIVE
(1 through 8)
Fast flashing green: Channel is in test access mode.
Slow flashing green: LED follows the ring signal.
Off: Channel is on hook (idle).
FAULT Red: Fault detected by the unit. See Table 10 on page 10 for troubleshooting procedures.
Off: No faults detected.
Warranty Control
Number Label
Indicates the beginning year and month of the equipment warranty. Also indicates the unit
revision number. For example, a warranty control number of “71203” indicates a warranty
beginning 1997 (7), in December (12), and the revision is “03.”
Bar Code Label Contains the serial number and part number of the equipment in both bar code and text formats.
PairGain
1
A
C
T
I
V
E
2
3
4
5
6
7
8
FAULT
FRC 754
CHAN UNIT
LIST 4
Status LEDs
Fault LED
Warranty control
number label
Bar code label

363-754-104-01, Revision 01 Product Overview
PG-Flex FRC-754 List 4 June 22, 1998 3
Specifications
Electrical Characteristics
Analog Impedance 600 Ω
Subscriber Drop 960 Ω(including 430 Ωfor the handset)
DC Loop Current ≥23 mA
Ringer Output 40 V RMS, 3 lines simultaneously, 5 REN each
End-to-End Loss -2.5 dB ± 1.0 dB at 1004 Hz
Lightning Protection Meets all requirements (GR-CORE-1089, Section 4)
Environmental
Operating Elevation –200 ft. to 13,000 ft. (–60 m to 4000 m)
Temperature and Humidity –40° F to +150° F (–40° C to +65° C)
5% to 95% (non condensing)
Physical
Weight 0.6 lb (0.3 kg)
Dimensions
Height 12.00 in. (30.5 cm)
Width 1.00 in. (2.5 cm)
Depth 4.50 in. (11.4 cm)

Product Overview 363-754-104-01, Revision 01
4 June 22, 1998 PG-Flex FRC-754 List 4
Operational Capabilities
The FRC-754 List 4 channel unit provides eight loop start or ground start POTS interfaces between the RT and
subscribers, and performs the following functions:
•64 kbps A-Law PCM encoding
•applies ringing voltage
•generates forward disconnect
•generates 12 kHz or 16 kHz meter tones
•detects an off-hook or ring-trip condition
•connects a subscriber loop to a metallic bypass pair
•protects against secondary surges
The subscriber line battery is supplied by a constant current supply. It is sufficient to operate a telephone set over
the indicated loop length. The battery feed can be disconnected and the loop opened to release subscriber
equipment when a forward disconnect signal is received fromthe FLC-704 List 4 COT line unit. The battery feed
polarity can also be reversed as a physical signal of far end supervision.
Circuit Operation
The following paragraphs define the FRC-754 List 4 circuit operation when using loop start for subscriber lines
or ground start for PBX lines. Each FRC-754 List 4 circuit has an associated LED that indicates when the line is
off-hook, idle, ringing, or under test (see Table 1 on page 2).
Loop Start Operation
The following section summarizes the loop start sequences for on-hook (idle), subscriber inititated outgoing calls,
subscriber received incoming calls, and busy conditions.
On-hook (Idle) Condition. Loop start idle condition is a Ring-lead negative and Tip-lead positive from the CO
with the same condition out of the RT toward the subscriber (see Table 2 for circuit interactions).
Subscriber Initiated Outgoing Call. The following occurs when the calling line goes off-hook (see Table 2
on page 4 for circuit interactions):
•loop current flows and is detected by the FRC-754 List 4 channel unit
•FLC-704 receives an off-hook signal from the RT
•FLC-704 generates an off-hook condition to the CO switch
•CO sends dial tone
•FRC-754 passes a dial pulse or Dual Tone Multi Frequency (DTMF) signal through the FLC-704 from the
subscriber and forwards these to the CO
Table 2. Circuit Interactions for an Idle Condition (Loop Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Circuit Idle No ringing ⇒No ringing ⇒
⇐On-hook ⇐On-hook

363-754-104-01, Revision 01 Product Overview
PG-Flex FRC-754 List 4 June 22, 1998 5
Subscriber Receives Incoming Call. The following occurs for an incoming call (see Table 4 for circuit
interactions):
•FLC-704 detects a ringing signal from the CO
•FLC-704 signals the FRC-754 which then connects ringing to the subscriber
•subscriber line goes off-hook and the FRC-754, through the FLC-704, provides an off-hook condition to the
CO switch
Busy Condition. Loop start busy condition at the RT is a Ring lead negative and a Tip lead positive with loop
current flowing. The same conditions occurs at the CO (see Table 5 for circuit interactions).
Table 3. Circuit Interactions When a Subscriber Initiates an Outgoing Call (Loop Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
CO Idle No ringing ⇒No ringing ⇒
Subscriber goes
off-hook ⇐Off-hook ⇐Off-hook
CO returns dialtone Dialtone ⇒Dialtone ⇒
Subscriber Dials ⇐DP or DTMF ⇐DP or DTMF
Table 4. Circuit Interactions When a Subscriber Receives an Incoming Call (Loop Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Subscriber Idle ⇐On-hook ⇐On-hook
CO generates ringing Ringing ⇒Ringing ⇒
Subscriber goes
off-hook ⇐Off-hook ⇐Off-hook
Ring trip No ringing ⇒No ringing ⇒
Table 5. Circuit Interactions for a Busy Condition (Loop Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Circuit busy No ringing ⇒No ringing ⇒
⇐Off-hook ⇐Off-hook

Product Overview 363-754-104-01, Revision 01
6 June 22, 1998 PG-Flex FRC-754 List 4
Ground Start Operation
The following section summarizes the ground start sequences for on-hook (idle), subscriber inititated outgoing
calls, subscriber received incoming calls, and busy conditions.
Idle Condition. Ground start idle condition is a Tip-lead open and Ring-lead negative from the CO and Tip lead
open and Ring-lead negative at the RT (see Table 6 for circuit interactions).
Subscriber Initiates Outgoing Call. The following occurs when a PBX requests service for an outgoing call
(see Table 7 for circuit interactions):
•PBX grounds Ring lead at the RT
•FRC-754 signals the FLC-704
•FLC-704 operates a Ring-ground relay that requests dial tone from the CO (this makes the circuit busy, or
seizes it, for outgoing calls, and blocks any incoming calls prior to the PBX dialing (that is, it prevents glare
where incomingand outgoing calls may occur simultaneouslyon the same line). Glare occurs when both ends
of a telephone line or trunk are seized at the same time.
•CO sends dial tone and grounds the Tip to signal the PBX to begin dialing
•FLC-704 detects Tip-ground, closes the loop between Tip and Ring, and signals the FRC-754 to send Tip
ground to the PBX
•PBX removes the original Ring-ground condition and completes the loop (Tip and Ring)
Table 6. Circuit Interactions for an Idle Condition (Ground Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Circuit Idle Tip - no ground
No ringing ⇒Tip - no ground No ringing ⇒
⇐Ring - no ground
On-hook ⇐Ring - no ground On-hook
Table 7. Circuit Conditions When a Subscriber Initiates an Outgoing Call (Ground Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
CO Idle Tip - No ground
No ringing ⇒Tip - No ground No ringing ⇒
Subscriber requests
dialtone ⇐Ring - ground On-hook ⇐Ring - ground On-hook
CO returns dialtone Tip - ground
Dialtone ⇒Tip - ground Dialtone ⇒
Subscriber Dials ⇐Ring - no ground
Off-hook
DP or DTMF
⇐Ring - no ground
Off-hook
DP or DTMF

363-754-104-01, Revision 01 Product Overview
PG-Flex FRC-754 List 4 June 22, 1998 7
Subscriber Receives Incoming Call. The following occurs for an incoming call (see Table 8 for circuit
interactions):
•FLC-704 detects a ringing signal from the CO, along with Tip-ground
•FLC-704 signal the FRC-754 to connect Tip-ground and ringing to the PBX
•PBX goes off-hook and the FRC-754, through the FLC-704 closes the loop between Tip and Ring, the CO
disconnects ringing and establishes an audio path
Busy Condition. Ground start busy condition at the RT is a Ring lead negative and a Tip lead positive with loop
current flowing. The same conditions occurs at the CO (see Table 9 for circuit interactions).
CLASS Features
PG-Flex supports on-hook transmission of analog signals. When Call ID (a CLASS feature) is activated, the CO
generates analog signalling toward the PBX between the first and second bursts of the ringing signal.
Forward Disconnect
The forward-disconnect functionreleases a called line that was left onhold or an answering set that requires a loop
open to be able to turn off.
Table 8. Circuit Conditions When a Subscriber Receives an Incoming Call (Ground Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Subscriber Idle ⇐Ring - no ground
On-hook ⇐Ring - no ground On-hook
CO seizes loop Tip - ground
No Ringing ⇒Tip - ground No Ringing ⇒
CO generates ringing Tip -ground
Ringing ⇒Tip -ground Ringing ⇒
Subscriber goes
off-hook ⇐Ring - no ground Off-hook ⇐Ring - no ground Off-hook
Ring trip Tip - ground
No ringing ⇒Tip - ground No ringing ⇒
Table 9. Circuit Conditions for a Busy Condition (Ground Start)
Operation CO Switch FRC-754 List 4 COCU FRL-754 List 4 RTCU Subscriber
Circuit busy Tip - ground
No ringing ⇒Tip - ground No ringing ⇒
⇐Ring - no ground
Off-hook ⇐Ring - no ground Off-hook

Installation and Test 363-754-104-01, Revision 01
8 June 22, 1998 PG-Flex FRC-754 List 4
INSTALLATION AND TEST
Unpacking
Upon receipt of the equipment:
1Unpack 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.
2Check the contents versus the packing list to ensure complete and accurate shipment. If the shipment is short
or irregular, contact PairGain as described in “Product Support” on page 11. If you must store the equipment
for a prolonged period, store the equipment in its original container.
Installing
1Insert each FRC-754 List 4 into the FRE-765 RT enclosure, then see if all LEDs on the channel unit:
•turn ON for approximately 2 seconds
•scan from top to bottom
•flash all ON, then OFF
If the LEDs do not follow the above sequence, see Table 10 on page 10.
2After the system has powered up, established HDSL synchronized communications, and no calls are in
progress, verify thatthe channel unit front panel indicators ACTIVE 1 through ACTIVE 8 and FAULT LEDs
are all off.
Provisioning
Provision the FRC-754 List 4 using the appropriate line unit technical practice. For each channel provisioned,
select the loop start of ground start option.
Observe normal electrostatic discharge precautions when handling electronic equipment. Do
not hold electronic plugs by their connector edges. Do not touch components or circuitry.
Observe normal electrostatic discharge precautions when handling electronic equipment. Do
not hold electronic plugs by their connector edges. Do not touch components or circuitry.
Use List 3 of higher PG-Flex CO and RT line units when activating the ground start feature.
To reduce power at the RT, the FRC-754 LEDs turn off after a two minute time-out period. Press
and hold the ACO button on the RT line unit for two seconds to turn on the LEDs for another
two minutes.

363-754-104-01, Revision 01 Installation and Test
PG-Flex FRC-754 List 4 June 22, 1998 9
Verify Installation
After the PG-Flex system is powered up and HDSL communication is synchronized:
1Verify that the front panel ACTIVE indicators are all OFF and the FAULT indicator is OFF (no calls are in
progress).
2Test the loop start circuits, as follows:
•Place an outgoing call for each subscriber circuit provisioned, and verify that the ACTIVE LED tracks
the progress of the call (refer to Table 1 on page 2 for front panel indications)
•Place an incoming call to each subscriber circuit provisioned, and verify that the ACTIVE LED tracks
the progress of the call (refer to Table 1 on page 2 for front panel indications)
3Test the ground start circuits, as follows:
•Place an outgoing call for each subscriber circuit provisioned, and verify that the ACTIVE LED tracks
the progress of the call (refer to Table 1 on page 2 for front panel indications)
•Place an incoming call to each subscriber circuit provisioned, and verify that the ACTIVE LED tracks
the progress of the call (refer to Table 1 on page 2 for front panel indications)

Installation and Test 363-754-104-01, Revision 01
10 June 22, 1998 PG-Flex FRC-754 List 4
Troubleshooting
Table 10 provides troubleshooting procedures based on indications displayed by the front panel indicators of the
FRC-754 List 4 channel unit.
Table 10. FRC-754 List 4 Channel Unit Troubleshooting Procedures
Indication Problem Action
FAULT LED ON The FRC-754 processor has
detected a fault.
Remove and reinsert the Channel Unit. If the FAULT LED does not extinguish,
replace the Channel Unit.
Troubleshooting based on customer-originated trouble reports
No Dial Tone,
Can’t Dial •faulty RT or COT Channel
Unit
•facility short/open
•CO switch problem
•Tip/Ring reversed at CO
1Lift the subscriber pair at the network interface. If dial tone is present and you
can place a call, refer the problem to the customer per local practice.
2If you cannot hear a dial tone or cannot place a call at the network interface
(with the subscriber pair lifted), check for a dial tone at the RT. If a dial tone is
present, check the pair between the RT and the network interface. If no dial tone
is present, replace the RT Channel Unit.
3If the problem still exists, reinsert the original RT Channel Unit and replace the
COT Channel Unit. Test for operation.
4If the problem still exists, refer the problem to the CO switch.
Phone Doesn’t
Ring •high-resistance subscriber
line short
•faulty RT or CO Channel
Unit
•loop length too long
1Lift the subscriber pair at the network interface. If ringing is present, refer the
problem to the customer per local practice.
2If ringing is not present, check for ringing at the RT. If ringing is present, check
the pair between the RT and the network interface. If no ringing is present,
replace the RT Channel Unit. If ringing is still not present, check a circuit on
another Channel Unit. If ringing is still not present, replace the RT Line Unit.
3If ringing is still not present at the RT, reinsert the original Channel Unit and
Line Unit. Test for ringing at the COT.
4Test for ringing into the COT from the CO switch. If no ringing is present, refer
the trouble to the CO switch. If ringing is present, replace the COT Channel Unit.
Test again for ringing at the network interface. If ringing is still not present,
contact PairGain technical assistance per “Product Support” on page 11.
5Verify the resistance of the copper loop between the RT Enclosure and the
network interface is less than 530 Ω.
Phone Doesn’t
Stop Ringing •faulty subscriber
instrument
•faulty RT Channel Unit
•loop length too long
1Test for ring trip at the network interface. If the ringing is tripped, refer the
trouble to the customer per local practice.
2If the ringing is not tripped, test for tripping at the RT. If ring trip does occur,
check the loop for excessive length. If ring trip does not occur, replace the RT
Channel Unit. If ring trip still does not occur, contact PairGain technical
assistance per “Product Support” on page 11.
3Verify the resistance of the copper loop between the RT Enclosure and the
network interface is less than 530 Ω.
Can’t Hear,
Can’t Be Heard •subscriber problem
•faulty RT or COT Channel
Unit
1Lift the subscriber line at the network interface and check the signal level. If
correct, refer trouble to the customer per local practice.
2If the level is too low, check the level at the RT. If the level is correct at the RT,
check the pair between the RT and the network interface. If the level is too low
at the RT, replace the RT Channel Unit.
3If the level is still too low, reinsert the original RT Channel Unit.
4Check the level at the COT coming from the CO switch. If it is correct, replace
the COT Channel Unit. If it is not correct, refer the problem to the CO regarding
the switch.
5If the level is still not correct, reinsert the original COT Channel Unit. Contact
PairGain technical assistance per “Product Support”.

363-754-104-01, Revision 01 Product Support
PG-Flex FRC-754 List 4 June 22, 1998 11
PRODUCT SUPPORT
This section contains product support and warranty information.
Technical Support
PairGain Technical Assistance is available 24 hours a day, 7 days a week by contacting PairGain Customer
Service Engineering group at:
During normal business hours (8:00 AM to 5:00 PM, Pacific Time, Monday through Friday, excluding holidays),
technical assistance calls are normally answered directly by a Customer Service Engineer. At other times, a
request for technical assistance is handled by an on-duty Customer Service Engineer through a callback process.
This process normally results in a callback within 30 minutes of initiating the request.
In addition, PairGain maintains a computer bulletin board system for obtaining current information on PairGain
products, product troubleshooting tips and aids, accessing helpful utilities, and for posting requests or questions.
This system is available 24 hours a day by calling [phone]. Transmission speeds up to 28.8 kbps are
supported with a character format of 8-N-1.
Warranty
PairGain Technologies warrants this product to be free of defects and to be fully functional for a period of 60
months from the date of original shipment, given correct 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 incorrect use or installation.
Do not try to repair the unit. 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 voids the warranty.
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.
14352 Franklin Avenue
Tustin, CA 92780
ATTN: Repair and Return Dept.
[phone]
PairGain continues to repair faulty modules beyond the warranty program at a nominal charge. Contact your
PairGain sales representative for details and pricing.
Telephone: [phone] or [phone]
Fax: [phone]

Abbreviations 363-754-104-01, Revision 01
12 June 22, 1998 PG-Flex FRC-754 List 4
FCC Compliance
This unit complies with the limits for Class B 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, can 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.
Refer to the installation section of the appropriate instruction manual for the unit you are installing to get
information on:
•Cabling
•Correct connections
•Grounding
Modifications
The FCC requires the user to be notified that any changes or modifications made to this device that are not
expressly approved by PairGain Technologies, Inc. may void the user's authority to operate the equipment.
All wiring external to the products should follow the provisions of the current edition of the National Electrical
Code
ABBREVIATIONS
2B1Q 2 binary bits encoded in one quaternary symbol
AWG American Wire Gauge
CLASS Custom Local Area Signaling Services
CO Central Office
COT Central Office Terminal
DS0 Digital Signal Level Zero (64 kb/s)
DTMF Dual Tone Multi-Frequency
HDSL High-bit-rate Digital Subscriber Line
MLT Mechanized Loop Testing
PBX Private Branch Exchange
PCM Pulse Code Modulation
PGTC Pair Gain Test Controller
POTS Plain Old Telephone Service
RMA Return Material Authorization
RT Remote Terminal

Corporate Office
14402 Franklin Avenue
Tustin, CA 92780
Tel: [phone]
Fax: [phone]
For Technical Assistance:
[phone]