PairGain PG-Flex FRC-753 4B User manual

PG-FLEX
EIGHT CHANNEL REMOTE TERMINAL
LOOP START/GROUND START UNIT
PAIRGAIN TECHNOLOGIES, INC.
ENGINEERING SERVICES TECHNICAL PRACTICE
SECTION 363-753-142-01
Model List Number Part Number CLEI Code
FRC-753 4B 150-1353-42 VARHCKTC--
PairGain
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A
C
T
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V
E
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4
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8
FAULT
FRC 753
CHAN UNIT
LIST

363-753-142-01, Revision 01
ii July 23, 1999 FRC-753 List 4B
Revision History of This Practice
©Copyright 1999 PairGain Technologies, Inc.
PairGain and PG-Flex are registered trademark of PairGain Technologies, Inc.
Information contained in this document is company private to PairGain Technologies, Inc., and shall not 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 July 23, 1999 Initial Release

363-753-142-01, Revision 01 Using This Technical Practice
FRC-753 List 4B July 23, 1999 iii
USING THIS TECHNICAL PRACTICE
Three types of messages, identified by icons, appear in the text.
INSPECTING YOUR SHIPMENT
Upon receipt of the equipment:
•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.
•Check the packing list to ensure complete and accurate shipment of each listed item. If the shipment is short
or irregular, contact PairGain as described in the Warranty. If you must store the equipment for a prolonged
period, store the equipment in its original container.
Notes indicate information about special circumstances.
Cautions indicate the possibility of equipment damage or the possibility of personal injury.
Electrostatic Discharge (ESD) Susceptibility symbols indicate that a device or assembly is
susceptible to damage from electrostatic discharge.

Table of Contents 363-753-142-01, Revision 01
iv July 23, 1999 FRC-753 List 4B
TABLE OF CONTENTS
Overview ____________________________________________________________________________ 1
Description and Features................................................................................................................... 1
Applications....................................................................................................................................... 2
Operational Capabilities...................................................................................................... 2
FRC-753 Functions............................................................................................... 2
Circuit Operation.................................................................................................. 3
Front Panel......................................................................................................................................... 4
Specifications .................................................................................................................................... 5
Installation and Test___________________________________________________________________ 6
Installing the FRC-753 into the RT Enclosure.................................................................................. 6
Provisioning the FRC-753 .................................................................................................. 6
Verify Operation ................................................................................................................. 6
Troubleshooting ______________________________________________________________________ 7
Subscriber Drop Testing.................................................................................................................... 7
Customer Reported Problems............................................................................................................ 8
Abbreviations ________________________________________________________________________ 9
Product Support _________________________________________________________Inside back cover

363-753-142-01, Revision 01 Overview
FRC-753 List 4B July 23, 1999 1
OVERVIEW
The PairGain®PG-Flex®FRC-753 List 4B Loop Start/Ground Start Channel Unit provides eight loop start or
ground start (LS/GS) channel interfaces for POTS between a PG-Flex Remote Terminal (RT) and subscribers.
You can provision each of the eight circuits separately for either loop start or ground start services. Provisioning
is done through the PG-Flex Line Unit Maintenance port.
DESCRIPTION AND FEATURES
The FRC-753 provides metallic test access to the subscriber line connection through an optional metallic bypass
pair. Perform metallic bypass testing either manually or through the Pair Gain Test Controller (PGTC). Features
of the FRC-753 are:
•eight LS/GS POTS subscriber interfaces
•64 kbps m-Law Pulse Code Modulation (PCM) encoding
•front panel Active LEDs
•front panel Fault LED
•PGTC compatibility
•Custom Local Area signalling Services (CLASS) support (for example, caller ID)
•line-side answer supervision support (reverse battery)
•forward disconnect
•distinctive ringing
•protection against secondary surges and power cross
•connection for a subscriber loop to a metallic bypass test pair
•application of ringing voltage
•detection of loop off-hook, ground start seizure, and Ring-Tip conditions

Overview 363-753-142-01, Revision 01
2 July 23, 1999 FRC-753 List 4B
APPLICATIONS
The FRC-753 can be configured to provide service in any one of the following ways:
•eight independent loop start subscriber lines
•eight ground start PBX lines
•a mixture of both loop start subscriber lines and ground start PBX lines
Figure 1 shows a typical system with loop start and ground start services.
Figure 1. Typical System with Loop Start and Ground Start Capabilities
Operational Capabilities
FRC-753 Functions
The FRC-753 provides eight POTS channel interfaces between the RT and the subscriber. Each FRC-753 detects:
•loop current
•Ring tip
•Ring ground
The subscriber line battery is supplied by a constant current supply. It is sufficient to operate a telephone set over
the indicated loop.The battery feed can be disconnected and the loop opened to a drop connection when a forward
disconnect signal is received from the FLC-703. The battery feed can also reverse the polarity of the output as a
physical signal of far end supervision.
The FRC-753 has protection from lightning and power crosses.
PG-Flex COT 8 Loop Start, Ground Start
or mixture of Loop Start and
Ground Start lines
PG-Flex RT2 Pair
HDSL, Power
Optional:
One additional pair
for Metallic Bypass
CO Battery
Alarm
Test Access
(PGTC)
8 Loop Start, Ground Start
or mixture of Loop Start and
Ground Start lines

363-753-142-01, Revision 01 Overview
FRC-753 List 4B July 23, 1999 3
Circuit Operation
The following paragraphs define the FRC-753 circuit operation when using loop start for subscriber lines or
ground start for PBX lines. Each FRC-753 circuit has an associated LED that indicates when the line is off-hook,
idle, ringing, or under test. See Table 1 on page 4.
Loop Start Idle. Loop start idle condition is a Ring lead negative and Tip lead positive from the COT shelf with
the same conditions out of the RT toward the subscriber. The following occurs when the calling line goes
off-hook:
•loop current flows and is detected by the FRC-753
•FLC-703 receives an off-hook signal from the RT
•FLC-703 generates an off-hook signal to the CO to begin current flow
•CO sends dial tone
•FRC-753 recognizes dial pulses or Dual Tone Multi Frequency (DTMF) signalling, from the subscriber and
forwards these as loop current breaks, or DTMF signalling, to the CO
The following occurs for an incoming call:
•FLC-703 detects a ringing signal from the CO
•FLC-703 signals the FRC-753 which then connects ringing to the subscriber
•subscriber line goes off-hook and the FRC-753, by means of the FLC-703, signals the CO to disconnect
ringing and establish an audio path
Ground Start Idle. Ground start idle condition is a Tip lead open and Ring lead negative into the COT and Tip
lead open and Ring lead negative at the RT. The following occurs when a PBX requests service for an outgoing
call by grounding the Ring lead at the RT:
•FRC-753 signals the FLC-703
•FLC-703 operates a Ring ground relay that requests dial tone from the CO (this makes the circuit busy, or
seizes it, for outgoing calls to prevent others from using it, for example, prevents glare where different users
can seize a line at the same time)
•CO sends dial tone and grounds the Tip to signal the PBX to begin dialing
•FLC-703 detects Tip ground, closes the loop between Tip and Ring, and signals the FRC-753 to send Tip
ground to the PBX
•PBX removes the original Ring ground condition and completes the loop (Tip and Ring)
The following occurs for an incoming call:
•FLC-703 detects a ringing signal from the CO, along with Tip ground
•FLC-703 signals the FRC-753 which then connects Tip ground and ringing to the PBX
•PBX goes off-hook and the FRC-753, by means of the FLC-703, signals the CO to disconnect ringing and
establish an audio path
Caller ID. When caller ID (a CLASS feature) is activated, the CO generates a signal to the subscriber between
the first and second bursts of the ringing signal only (for example, PG-Flex supports on-hook transmission).
Forward-Disconnect Function. The forward-disconnect function releases a called line that was left on hold
or an answering set that requires a loop open to be able to turn off.

Overview 363-753-142-01, Revision 01
4 July 23, 1999 FRC-753 List 4B
FRONT PANEL
Figure 2shows the FRC-753 front panel. Table 1 liststhe different states and indications for the FRC-753 Channel
Unit front panel LEDs.
Figure 2. FRC-753 Front Panel
To reduce power at the RT, the LEDs extinguish after a 2-minute timeout period. Press and hold the ACO button
on the RTLU for two seconds to re-activate the LEDs for another two minutes.
Table 1. FRC-753 Front Panel LEDs
LEDs State Indicates
ACTIVE (1 through 8) Solid green Channel is off hook.
Fast flashing green Channel is switched to the test pair.
Slow flashing green Channel is ringing.
Off Channel is on hook.
FAULT Red Fault detected by the unit.
Off No faults detected.

363-753-142-01, Revision 01 Overview
FRC-753 List 4B July 23, 1999 5
SPECIFICATIONS
Electrical Characteristics
Analog Impedance 600 Ω
Subscriber Drop 530 Ω+ 430 Ωhandset
DC Loop Current 23 mA
Ringer Output 40 V RMS, 3 lines simultaneous, 5 REN each
End-to-End Loss -2.5 dB ± 1.0 dB
Lightning Protection GR-CORE-1089, Section 4
Environmental
Operating Elevation -200 ft. to 13,000 ft. (-60 m to 4,000 m)
Temperature -40° F to +150° F (-40° C to +65° C)
Humidity 5 percent to 95 percent noncondensing
Physical Characteristics
Weight 0.6 lb. (0.3 kg)
Height 12.0 in. (30.5 cm)
Width 1.0 in. (2.5 cm)
Depth 4.5 in. (11.4 cm)

Installation and Test 363-753-142-01, Revision 01
6 July 23, 1999 FRC-753 List 4B
INSTALLATION AND TEST
INSTALLING THE FRC-753 INTO THE RT ENCLOSURE
1Insert the FRC-753 into the RT Enclosure and observe that all LEDs:
•turn On for approximately two seconds
•scan from top to bottom
•turn Off
If the LEDs do not follow the above sequence, refer to Table 1 on page 4.
Provisioning the FRC-753
Provisionthe FRC-753 usingthe FLL-712List 3 COLine Unit practice. For each channelprovisioned, select loop
start or ground start.
Verify Operation
Verify the following after the system is powered up and HDSL communication is synchronized:
1Observe that the front panel Active indicators are alloff and the Faultindicatoris off (no callsare inprogress).
2Test circuits for loop start:
aPlace an outgoing call for each subscriber circuit provisioned and observe that the Active LED tracks the
progress of the call.
bPlace an incoming call for each subscriber circuit provisioned and observe that the Active LED tracks
the progress of the call.
3Test circuits for ground start, circuits must be provisioned for ground start:
aPlace an outgoing call for each subscriber circuit provisioned and observe that the Active LED tracks the
progress of the call.
bPlace an incoming call for each subscriber circuit provisioned and observe that the Active LED tracks
the progress of the call.
Observe normalelectrostatic discharge precautions when handling electronic equipment.Do
not hold electronic plug-ins by their edge. Do not touch components or circuitry.
Use List 3 or higher PG-Flex CO and RT LUs when activating the ground start feature.

363-753-142-01, Revision 01 Troubleshooting
FRC-753 List 4B July 23, 1999 7
TROUBLESHOOTING
SUBSCRIBER DROP TESTING
For PG-Flex subscriber drop testing from the CO, select and connect any subscriber drop to a metallic test pair at
the RT. PG-Flex extends this connection to the COT where it can be switched onto the test access bus or to the
corresponding subscriber line on the COT channel card.
Activate test access through the RS-232 maintenance port located on the front of the COT Line Unit using an
ASCII terminal.
TheFRC-753 Channel Unit frontpanel FaultLEDs is On.The FRC-753 has detecteda fault. Remove and re-insert
the Channel Unit. If the Fault LED does not extinguish, replace the Channel Unit.

Troubleshooting 363-753-142-01, Revision 01
8 July 23, 1999 FRC-753 List 4B
CUSTOMER REPORTED PROBLEMS
Table 2 provides troubleshooting procedures based on customer reported problems.
Table 2. FRC-753 RT Channel Unit Troubleshooting
Problem Cause Action
No dial tone,
can not dial •faulty RT or COT Channel
Unit
•facility short/open
•CO switch problem
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 dial tone or cannot place a call at the network interface (with
the subscriber pair lifted), check for dial tone at the RT. If 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, re-insert 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 does
not 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 RTLU.
3If ringing is still not present at the RT, re-insert the original Channel Unit and
Line Unit. Test for ringing at the COT shelf.
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 (refer to “Technical Support” on Inside
back cover).
5Verify the resistance of the copper loop between the RT Enclosure and the
network interface is less than 530 Ω.
Phone does
not 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 (refer to “Technical Support” on Inside back cover).
3Verify the resistance of the copper loop between the RTE and the network
interface is less than 530 Ω.
Can not
hear, can
not 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, re-insert the original RT Channel Unit.
4Check the level at the COT shelf 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, re-insert the original COT Channel Unit. Contact
PairGain technical assistance (refer to “Technical Support” on Inside back
cover).

363-753-142-01, Revision 01 Abbreviations
FRC-753 List 4B July 23, 1999 9
ABBREVIATIONS
ACO Alarm Cut-off Switch
CLASS Custom Local Area Signalling Services
CO Central Office
COLU Central Office Line Unit
COT Central Office Terminal
DTMF Dual Tone Multi Frequency
LS/GS Loop Start/Ground Start
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

PRODUCT SUPPORT
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 - 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.
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 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.
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 at [phone].
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.
PairGain continues to repair faulty modules beyond the warranty program at a nominal charge. Contact your
PairGain sales representative for details and pricing.
FCC COMPLIANCE
This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part
15 ofthe FCCRules. These limits aredesigned toprovide reasonable protection againstharmful interferencewhen
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.
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 product(s) should follow the provisions of the current edition of the National Electrical
Code.
Telephone: [phone] or [phone]
Fax: [phone]

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