Pairgain Hlu-231 User manual

PAIRGAIN TECHNOLOGIES Section 150-231-106

Technical Practice Revision 05

Engineering - PLANT Series February 3, 1995

05 Page 1

PAIRGAIN™TECHNOLOGIES HIGAIN™LINE UNIT

MODEL HLU-231 Issue 1

List 6, PairGain #150-1111-06 CLEI Code: T1LIE1N4AA

CONTENTS PAGE

A. PRODUCT OVERVIEW 2

1. DESCRIPTION AND FEATURES 2

2. APPLICATIONS 2

3. SPECIFICATIONS 2

4. CERTIFICATION 3

5. WARRANTY 3

B. FUNCTIONAL DESCRIPTION 4

6. OPERATIONAL CAPABILITIES 4

7. SYSTEM OPTION SETTINGS 8

8. LOOPBACK DESIGN DESCRIPTION 12

C. INSTALLATION AND TEST 14

9. INSTALLATION OPTIONS 14

10. TESTING PROCEDURES 15

CAUTION

This product incorporates static sensitive components.

Proper electrostatic discharge procedures must be

followed.

Figure 1. HLU-231, List 6 Front Panel. The PairGain

HLU-231 is the local unit used in conjunction with the

HRU-412 remote unit to provide a complete HiGain HDSL

system.

Section 150-231-106

Revision 05

Page 2

A. PRODUCT OVERVIEW

1. DESCRIPTION AND FEATURES

1.01 PairGain’s HiGain Line Unit Model HLU-231

Issue 1, List 6 (Figure 1) is the Central Office

(CO) side of a repeaterless T1 transmission system.

When used in conjunction with an HRU-412 HiGain

Remote Unit, the system provides 1.544 Mb/s

transmission on two unconditioned copper pairs over

the full Carrier Serving Area (CSA) range. The CSA

includes loops up to 12000 feet of AWG 24 or 9000

feet of AWG 26 wire, including bridged taps. The

HiGain system uses HDSL (High-bit-rate Digital

Subscriber Line) transmission technology as

recommended by Bellcore TA-TSY-001210. HiGain

complies with TR-TSY-000063 (Network Equipment

Building System (NEBS) Generic Equipment

requirements) and TR-TSY-000499 (Transport

System Generic Requirements - TSGR) common

requirements.

1.02 Revision History of this practice.

Revision 05—February 3, 1995

a) Changed the default setting of the DS1 line

code to AMI.

b) This change initiated by software version

1.4.

1.03 HLU-231, List 6, Issue 1 features:

• Selectable DSX-1 Pre-equalizer

• -130 VDC Line Power for HRU-412

• Front Panel HDSL S/N Margin Display

• Selectable Loopback activation codes

• RS-232 maintenance port

• Non-volatile front-panel operator setup

• Front Panel DS1 splitting & brdg access

• Lightning and power cross protection on

HDSL interfaces

• 784 kbps full-duplex 2B1Q HDSL

transmission on two pairs

• Front panel status indicating LED

• On / Off front panel display power cycling

• DS1 LOS detector (125 consecutive zeros)

• Margin threshold alarm

• HAIS & SAIS options

• Easy return to factory default user settings

• New T1 transceiver chip

• Circuit ID option.

2. APPLICATIONS

2.01 HiGain provides a cost-effective, easy to

deploy method for delivering T1 High Capacity

Digital Service (HCDS) over metallic pairs. The fiber-

like quality service is deployed over two

unconditioned, non-loaded copper pairs. Conventional

in-line T1 repeaters are not required. Cable pair

conditioning, pair separation and bridged tap removal

are not required.

2.02 The general guidelines require that each loop

have less than 35 dB of loss at 196 kHz, with

135 ohm driving and terminating impedances. The

HiGain system operates with any number of other T1,

POTS, Digital Data Service (DDS) or other HiGain

Systems sharing the same cable binder group.

HiGain systems can be used with customers requiring

DS1 service on a temporary or permanent basis.

HiGain also provides a means of quickly deploying

service in advance of fiber-optic transmission

systems. With HiGain, service can be provided within

hours. Fiber optic systems can be installed at a

leisurely pace and cut-over from HiGain when

convenient to do so. The HiGain system can then be

easily removed and utilized elsewhere.

3. SPECIFICATIONS

HDSL Line Code

784 kbps 2B1Q full duplex

HDSL Output

+13.5 dBm ± 0.5 dB at 135 ohms

HDSL Line Impedance

135 ohms

Maximum Provisioning Loss

35 dB at 196 kHz, 135 ohms

Line Clock rate

Internal Stratum 4 clock

HDSL Startup Time

30 seconds (typical), 60 seconds (maximum)

One-way DS1 Delay

<220 microseconds

DSX-1 Line Impedance

100 ohms

DSX-1 Pulse Output

12V pk-pk for EXTERNAL equalizer or pre-

equalized for 0-655 feet of ABAM

Issue 1, Section 150-231-106

Revision 05

Page 3

DSX-1 Input Level

+1.5 to -7.5 dB

DS1 Line Rate

1.544 Mbps ± 200 bps

DS1 Line Format

AMI, B8ZS or ZBTSI

DS1 Frame Format

ESF, SF or unframed

Power Consumption

14 Watts (typical), 18 Watts (maximum)

Heat Dissipation

6 Watts (typical), 8 Watts (maximum)

Fusing

Internal, connected to FUSEALARM output on pin

Span Voltage

-136Vdc ± 4 Vdc

Margin Indicator: displays span SNR margin for

both spans relative to 10-7 BER operation

Electrical Protection

Secondary surge protection on DS1 and HDSL

ports

Power cross protection on HDSL ports

Operating Temperature and Humidity

-40 to 65° Celsius, 5 to 95% (non-condensing)

Mounting

AT&T 220 type or equivalent

Dimensions

Height: 5.9” (15 cm)

Width: 1.4” (3.5 cm)

Depth: 10” (25.4 cm)

4. CERTIFICATION

4.01 FCC compliance: The HLU-231 has been

tested and found to comply 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.

5. WARRANTY

5.01 PairGain Technologies warrants this product

to be free of defects and to be fully functional

for a period of 24 months from the date of original

shipment, given proper installation. 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 voids 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.

(714) 638-0031

Section 150-231-106

Revision 05

Page 4

B. FUNCTIONAL DESCRIPTION

6. OPERATIONAL CAPABILITIES

6.01 HiGain utilizes PairGain’s 2B1Q HDSL

transceiver systems to establish two full-

duplex 784 kbps data channels between the HLU-231

and a remotely mounted HRU-412 HiGain Remote

Unit. This provides a total capacity of 1.568 Mbps

between the two units.

6.02 A block diagram of the HLU-231 is shown in

Figure 2. The HiGain HLU-231 receives a

1.544 Mbps DS1 data stream from the DSX-1 digital

cross connect interface. The HLU contains a DS1

frame synchronizer controlled by an 8-bit micro

controller that determines the type of framing on the

DS1 stream and synchronizes to it. The HLU-231

recognizes SF(including D4) or ESF framing. When

the data is unframed, the HLU-231 arbitrarily defines a

frame bit.

6.03 The HLU-231 contains a demultiplexer that

generates two parallel 784 kbps data streams.

The data streams contain HDSL frames that are

nominally 4704 bits (6 milliseconds) in length. The

HDSL frames contain a 14-bit Frame Sync Word

(FSW), 6-bit Cyclic Redundancy Check (CRC), 21-bit

operations channel and DS1 payload. The DS1

stream is separated into two parallel streams that

comprise the payloads of the HDSL channels. HDSL

channel 1 contains the DS1 time slots 1 thru 12.

HDSL channel 2 contains the DS1 time slots 13 thru

24 The 8 kbps frame bits of the DS1 stream are

included on both HDSL channels.

6.04 The two formatted HDSL channels are

passed to the HDSL transceivers which convert them

to 2B1Q format on the HDSL lines. The 2B1Q line

code is designed to operate in a full-duplex mode on

unconditioned pairs. The transceiver’s echo canceler

and adaptive equalizer receive the signal from the

remote end in the presence of impairments and noise

on the copper pairs.

Figure 2. HRU-231, List 6 Block Diagram. PairGain’s HDSL technology provides full-duplex services at standard T-1 rates

over copper wires between an HLU and an HRU, which comprise one HiGain system.

Issue 1, Section 150-231-106

Revision 05

Page 5

6.05 The received HDSL channels are processed

by the transceiver and then passed on to the

HLU-231 multiplexer module. The multiplexer

provides frame synchronization for each of the two

HDSL channels. The multiplexer and HDSL

transceivers work under control of the HLU-231 micro

controller and compensate for data inversions caused

by tip-ring reversals and for channel swaps caused by

pair reversals. The HiGain system allows for tip-ring

or pair reversals, but does not tolerate split pairs. By

synchronizing to the FSW of each channel, the

multiplexer can reconstruct the original 1.544 Mbps

DS1 stream from the payloads of the two HDSL

channels. The CRC fields on the HDSL streams allow

the HLU-231 to determine if errors are present on the

channel due to excessive impairments on the HDSL

pairs, or due to excessive impulse or crosstalk noise.

6.06 The multiplexer removes data link messages

from the HDSL channels and pass them to

the micro controller. This mechanism allows

operations messages and status to be exchanged

between the HLU-231 and the HRU-412 remote unit.

6.07 The reconstructed HDSL data channel is

buffered in a first-in-first-out buffer (FIFO)

within the multiplexer. A frequency synthesizer in

conjunction with the FIFO regulates the output bit rate

and reconstructs the DS1 clock at the exact rate

received from the remote end. The HiGain system

operates at DS1 rates of 1.544 Mbps with up to ±200

bps of offset.

6.08 A DSX-1 interface driver converts the DS1

channel to an AMI or B8ZS format, as

determined by the T1 input data to the HLU (when in

AUTO mode) or by the setting. The DSX-1 equalizer

is programmable to five different lengths as

determined by the distance between the HLU and the

DSX-1 interface. This provides CB-119 compliant

pulses at the DSX-1 interface over a range of 0-655

feet of ABAM cable.

6.09 The HLU-231 contains two separate power

converters. The main power supply converts

-48V local battery to logic power for the HLU-231

circuits. The line power supply converts the -48V

battery to a -130VDC feed that provides simplex

power feed on the two line interfaces. The line power

supply can be turned on or off by the micro controller

and is automatically shut down in the presence of line

short circuits or micro controller failure.

6.10 The three most important power demands of

an HLU-231 on the shelf power supply are its

maximum power consumption, its maximum power

dissipation and its maximum current drain. These

three parameters for the HLU-231, on a per slot and

per shelf basis, are as follows:

Maximum Power Dissipation

• Per Slot = 8.0 Watts

• Per Shelf = 104 Watts

Maximum Power Consumption

• Per Slot = 18 Watts

• Per Shelf = 234 Watts

Maximum Current Drain

• Per Slot = 0.423 Amps

• Per Shelf = 5.5 Amps.

Note that the worse case conditions under which

these parameters were measured include a 9,000 ft.

#26 AWG loop, 60 mA of CPE current, a fully loaded

13-slot shelf, and a 42.5 V shelf battery voltage.

6.11 The Maximum Power Dissipation measures

the power that is converted into heat build up

within the unit. It contributes to the total heat

generated in the space around the unit. It is used to

determine the maximum number of fully loaded

shelves per bay that does not exceed the maximum

allowable power dissipation density in Watts/sq. ft.

6.12 In Central Office (CO) locations, the

maximum power dissipation for open faced,

natural convection cooled mountings is limited to 120

Watts/sq. ft. per Section 4.2.3 of the NEBS standard

TR-NWT-000063. The footprint of a 13-slot, 23-inch

HLU-231 shelf is 7.024 sq. ft. Thus the maximum bay

dissipation is limited to 840 Watts. At 104 Watts per

shelf, this limits the number of fully loaded HLU-231

shelves to eight per bay. Note that this is a worse

case situation in that it assumes the entire CO is

subjected to the maximum power density. Conditions

other than these worse case ones would permit

increasing the number of shelves per bay without

jeopardizing the CO’s thermal integrity.

6.13 The thermal loading limitations imposed when

using the HLU-231 in CEVs or other

enclosures are determined by applying the HLU-231’s

power parameters to the manufacturer’s requirements

for each specific housing.

6.14 The Maximum Power Consumption is the total

power that the HLU-231 consumes or draws

from its -48 V shelf power source. This parameter is

needed when the 231 is located remote to its serving

CO. It determines the battery capacity required to

maintain an 8-hour stand-by battery reserve for

emergency situations. It thus limits the maximum

number of plugs per remote enclosure. Use the above

data to perform this analysis on a case by case basis.

Section 150-231-106

Revision 05

Page 6

6.15 The Maximum Current Drain is the maximum

current drawn from the shelf power supply

when it is at its minimum voltage (42.5 V). This

determines the shelf fusing requirements. HLU-231

shelves are fused at 10 amps. A fully loaded shelf of

13 HLU-231s draws 5.5 amps in the worst case. This

is well within the 10 amp fuse limit.

6.16 A 9-pin RS-232 (DB-9) connector is provided

on the front panel (see Figure 3). This

connector provides access to HiGain’s maintenance,

provisioning and performance monitoring interface. A

very basic interface is available via a ‘dumb terminal’.

Figures 6 through 13 show the menu selections that

are available from the terminal. Tables 9 and 10

define the various terms used in the screen displays.

An enhanced interface is available with a ‘smart’ PC-

based interface and the HiGain Maintenance diskette

that is available from PairGain. The port is configured

as DCE with 8 data bits, 1 stop bit and no parity.

Striking the SPACE bar several times invokes

autobaud from 1200 to 9600 bps.

6.17 The normally open alarm contacts available

across pins 20 and 21 comprise the HLU-

231’s Minor Alarm output. These alarm contacts close

for any of the following alarm conditions. Since more

than one alarm condition can exist at any given time

but only one message can be displayed, the alarms

are listed as follows in their order of priorities. Only

the highest priority alarm is displayed if more than one

alarm condition exists. The ALRM message precedes

every specific alarm condition.

Figure 3. HLU-231, List 6 DB-9 Pin-Outs. A standard

RS-232 (DB-9) connector on the front panel provides

access to the menu interface feature via a dumb terminal.

1) ALRM LOSW: Either HDSL loop loses

sync.

2) ALRM LLOS: Loss of the HLU T1 input

signal.

3) ALRM RLOS: Loss of HRU T1 input signal

4) ALRM H1(2)ES: HDSL Loop 1 or Loop 2

has exceeded the 24-hour user-selected

Errored-Seconds CRC threshold

5) ALRM DS1: The total number of bipolar

violations (BPV) at the HLU and HRU T1

inputs have exceeded the 24-hour user-

selected threshold.

6) ALRM MAL1(2): The margin on HDSL

Loop 1 or Loop 2 has dropped below the

minimum threshold value set by the dumb

terminal MARGIN ALARM THRES; as

described in Section 7.

6.18 The HLU 231’s STATUS LED flashes RED for

the duration of a minor alarm condition.

Alarms 4 and 5 can be inhibited by selecting NONE

for the ESAL system option. See Section 7 for System

Settings information. The MAL(X) alarm can be

disabled by setting the margin alarm threshold to 0. A

minor alarm can be retired by executing the ACO

option. This is accomplished by pressing the SEL

button on the front panel. This turns the alarm off and

replaces the ALRM message by the ACO message.

The second part of the ALRM message, which defines

the cause of the alarm, remains. Both messages

remain until the alarm condition clears or another

alarm occurs.

6.19 Note that when both HDSL loops detect a

Loss of Sync Word (LOSW), a minor alarm

condition exists but because the HLU enters a self

test cycling mode, the front panel LED lights yellow

instead of red and the SELF TEST message is

displayed instead of the ALRM message.

6.20 Setting the ALM option to DIS only prevents

the alarm relay from operating on a minor

alarm event. The STATUS LED still flashes red and

the ALRM message is still displayed.

6.21 Pin 32, FUSEALARM, is driven to -48 V and

the front panel STATUS LED turns red

whenever the on board fuse opens.

Issue 1, Section 150-231-106

Revision 05

Page 7

6.22 The HLU-231’s front panel tri-color STATUS

LED has the following states:

• GREEN - Normal Operation

• FLASHING GREEN - HDSL Acquisition

• FLASHING RED - Minor Alarm (For

conditions see Paragraph 6.17)

• RED - FUSEALRM

• YELLOW - Self Test in process or an HLU

loopback in effect (CREM or NLOC).

• FLASHING YELLOW - The HLU is in an

ARMED state.

6.23 Pressing both the MODE and SEL

pushbuttons on the front panel for at least

three seconds initiates a MANUAL loopback session.

This session allows the user to SEL one of four

HiGain loopbacks. The message, MAN LPBK,

appears on the front panel display followed by the

message NLO?. If the SEL button is now depressed,

an NLOC loopback is executed and the message

changes from NLO? to NLOC. If the MODE button is

depressed instead of the SEL button, NLO? is

replaced by NRE?. This now allows an NREM

loopback to be executed with the SEL button.

Pressing the MODE button two more times yields the

CRE? (CREM) and CLO? (CLOC) customer loopback

options respectively. This interactive button procedure

permits any of the four HiGain loopback to be

executed. Once a loopback is executed, it can be

terminated and the next loopback option presented by

pressing the MODE button. If neither button is

depressed for a period of 30 seconds and no

loopback is active, this manual loopback session

terminates and the normal margin displays reappear.

If any loopback is in effect, this 30 second time-out is

inhibited. The manual interactive loopback session

continues and the loopback in effect remains active

until it times out, in accordance with the user LBTO

option setting, or another loopback is selected. Only

1 loopback can exist at any given time. Pressing both

buttons, again for three seconds, terminates any

active loopback, ends the MANUAL loopback session

and returns the display to normal. Note that these

same four loopbacks can be initiated from RS-232

maintenance port by choosing the LOOPBACK

MODE, option D, from the main menu. This displays

the Loopback Menu, shown in Figure 13, from which

any of the four loopbacks can be initiated.

Section 150-231-106

Revision 05

Page 8

7. SYSTEM OPTION SETTINGS

7.01 The HLU-231 contains non-volatile RAM

which stores the system option settings. No

dip-switches or jumpers are required to set the HLU-

231 configuration. The options are set via

pushbuttons on the front panel, through the RS-232

interface, or from the NMA interface and are retained

if shelf power is lost or if the HLU-231 is unplugged.

Table 1 lists the HLU-231 option settings. Note that

only those options enclosed by quotes can be set by

the front panel buttons. All 14 options can be set via

the front panel RS-232 port. Figure 8 shows the

Systems Settings menu used to set these options

from the RS-232 port. The settings with an asterisk

(*) in the second column represent the factory default

settings.

7.02 The SETUP (MODE and SEL) momentary

pushbuttons are used to set the four options

shown in quotes in Table 1 from the front panel. To

initiate an OPTION SETTING mode, depress the

MODE button for one second and release. The

message displayed on the front panel alternates

between the system parameter and its current setting.

Pressing the SEL button steps the display through all

possible settings (one at a time) of the MODE

(parameter) being displayed. After the desired setting

has been chosen, depress MODE. This does two

things. First it updates the current displayed mode to

the setting chosen. It then selects the next

configurable parameter. After the last parameter has

been selected, the displays shows CONF/NO. If the

MODE button is now depressed, none of the changed

parameters are installed. If the SEL button is

depressed, a YES message is displayed and the

chosen changes are installed. In either case the

display returns to its normal mode. The display also

returns to its normal mode, without installing any new

changes, if neither button is depressed for 30

seconds.

7.03 All 14 user options can be set to the factory

default values by pressing the SEL button for

six seconds until the message: “DFLT NO” appears.

To set the default values, press the SEL button while

the “DFLT NO” message is displayed. “DFLT YES”

will be displayed, indicating the factory default values

are now in effect. To terminate the DFLT mode

without setting the factory default values, press the

MODE button or do nothing for 30 seconds. The latter

returns the display to its normal state.

7.04 Pressing the MODE button for 3 or more

seconds causes the display to scroll through

the HLU’s software version number, its List #, the type

of frame pattern being received from the DSX-1, the

line code setting of the HLU and all 14 option settings.

See Table 8 for these additional messages. The line

code is the actual DS1 line code being received by the

HLU if the DS1 code is set to AUTO. Otherwise it

simply mimics either of the two DS1 code settings;

AMI or B8ZS.

7.05 The following three user options must be set

with a dumb or smart terminal: CIRCUIT ID,

DS0 BLOCKING and MARGIN ALARM

THRESHOLD.

7.06 The CIRCUIT ID option is set by choosing the

“H” option from the dumb terminal’s main

menu shown in Figure 6. The message “enter circuit

ID # 24 characters max” follows the “H” selection. Hit

the return key after entering the chosen set of alpha-

numeric ID characters. Then chose “C” to confirm.

Note if more than 24 characters are entered, a “beep’

is emitted and only the first 24 characters are

accepted. The ID appears in all HLU screens as

shown in Figures 6 through 13. The ID does not

appear on the HRU screens when the maintenance

port is accessed at the remote unit. Note that the

Circuit ID is not set to its default (all blanks) setting

when the DFLT setting option is utilized.

7.07 To set the DS0 BLOCKING option, first select

the SYSTEMS SETTINGS (“C” choice) from

the main menu. The menu shown in Figure 8 appears.

Now enter the letter “B” shown in parenthesis of the

DS0 blocking selection. The DS0 channels are

blocked or unblocked by entering each channel’s

number. Multiple channels can be selected by

inserting a space between each entry. After all the

new settings have been made, enter “E” for exit and

then “C” for confirm. The new choices are now

installed. If DS0 blocking is invoked in a HiGain

system that has an earlier HRU that does not support

the blocking option, blocking will only occur at the DS1

output of the HLU. The HRU’s DS1 output will not be

blocked. Also, all blocked channels are opened for all

HiGain loopback tests. This allows the standard full

bandwidth T1 loopback tests to be performed.

7.08 To set the MARGIN ALARM THRESHOLD

select “G” from the system settings menu.

Enter the desired minimum acceptable alarm

threshold from the 0 to 15 dB range. This causes a

minor alarm to occur (see paragraph 6.17) if either the

margin on HDSL loop 1 (MAL1) or loop 2 (MAL2)

drops below the selected threshold value. Since the

margin can never drop below 0, choosing “0” for the

margin threshold turns the margin alarm off.

Issue 1, Section 150-231-106

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7.09 The other dumb terminal system settings are

set in a similar manner. Simply enter the letter

in parenthesis of the parameter to be changed. Each

entry of this letter scrolls the parameter to its next

value. Hit the enter key after each selection is made.

After all selections have been made, enter “E” and

then “C” to the resulting Confirm message. This

activates the new choices and returns control to the

main menu.

7.10 The new T1 transceiver chip in this HLU 231,

List 6 unit and the equivalent versions of the

companion HRU-412 unit allows each unit to process

both B8ZS and AMI code inputs, regardless of the

DS1 code setting (AMI or B8ZS). Earlier units cause

input BPVs if B8ZS patterns are processed while in

AMI mode. When the newer units are in AMI mode,

they can receive B8ZS but can only transmit AMI. For

this reason, mixed systems will respond differently in

each direction for B8ZS inputs when in their AMI

mode.

7.11 The SELF-TEST mode that occurs when both

HDSL loops are not in sync has been

enhanced to include the input DS1 transceiver chip in

the self test procedure. This process can cause the

AIS pattern, that is normally transmitted from the HLU

during these out of sync intervals, to exhibit

occasional BPVs.

7.12 The HAIS option provides two choices for the

T1 transmit outputs at both the HLU & HRU

for HDSL loss of sync conditions. The “1LP” choice

causes the AIS pattern to be transmitted at both T1

outputs when either of the two HDSL loops

experience an out of sync (LOSW) condition or when

a margin alarm occurs. This choice causes the 12

channels on the surviving loop to be lost as they are

replaced by the AIS pattern. However it does allow

both down and upstream equipment to be made

aware of the loss of one HDSL loop or a loop with low

margin. This is the preferred setting to be able to

initiate an AIS state with just one conductor open in

either of the HDSL pairs. Short loops, below about 16

dB of loss at 200 kHz, can remain in sync with one

conductor open. Since the loop is still in sync, no

LOSW condition occurs. However, the margin on a

one conductor loop drops about 5 to 10 dB. Thus if

the Margin alarm is set to 5 dB below the normal

margin at turn-up, then when one conductor does

open, a margin alarm occurs and causes the AIS

condition. This alerts the maintenance personnel of

the problem. The “2LP” choice requires both HDSL

loops to be out of sync (LOSW) before the AIS signal

is transmitted. This choice preserves the integrity of

the 12 surviving channels when just one loop is lost.

The 12 channels from the loop that is lost are

replaced by all ones.

7.13 All user options that affect the operation in

both the HLU & HRU, such as HAIS, SAIS &

DS0 blocking, will not be available in older versions of

the HRU that do not support these newer options.

Section 150-231-106

Revision 05

Page 10

TABLE 1. SYSTEM OPTION SETTINGS

Mode Selection Description

EQL EXT* Replaces the internal equalizer with a 12 Vp/p driver for external

equalizers.

0 Sets Equalizer to DSX-1 for 0-133 feet.

133 Sets Equalizer to DSX-1 for 133-266 feet.

266 Sets Equalizer to DSX-1 for 266-399 feet.

399 Sets Equalizer to DSX-1 for 399-533 feet.

533 Sets Equalizer to DSX-1 for 533-655 feet.

LPBK DIS Configures HiGain to ignore all in-band “smart-jack” loopback commands.

ENA* Enables HiGain to recognize all in-band “smart-jack” loopback commands.

SPLB GNLB* Configures HiGain to respond to the generic 3/4 in 7 in-band loopback

codes.

A1LB&A2LB Configures HiGain to respond to the Teltrend addressable repeater in-

band loopback codes.

A3LB Configures HiGain to respond to the Wescom addressable repeater in-

band loopback codes.

A4LB Configures HiGain to respond to the Wescom Mod 1 addressable

repeater in-band loopback codes.

A5LB Configures HiGain to respond to the Teltrend Mod 1 addressable

repeater in-band loopback codes.

PWRF DIS Disables powering to the HRU.

ENA* Enables powering to the HRU.

ZBTS ON Tells HiGain that the ESF frame is operating in its ZBTSI mode.

OFF* Tells HiGain that the ESF frame is operating in its normal non-ZBTSI

mode.

ESAL 17 Activates (closes) the ALRM output relay contacts on pins 20 & 21 and

flashes the red STATUS LED when 17 Errored Seconds (ES) (17 HDSL

CRC errors on either HDSL loop or a total of 17 BPVs) occur within a 24-

hour period.

170 Activates (closes) the ALRM output relay contacts on pins 20 & 21 and

flashes the red STATUS LED when 170 ES (170 HDSL CRC errors on

either HDSL loop or a total of 170 BPVs) occur within a 24-hour period.

NONE* Prevents generation of a minor alarm due to excessive Errored Seconds.

LBTO NONE Disables automatic time-out cancellation of all loopbacks.

20 Sets automatic cancellation of all loopbacks to 20 minutes after initiation.

60* Sets automatic cancellation of all loopbacks to 60 minutes after initiation.

120 Sets automatic cancellation of all loopbacks to 120 minutes after initiation.

ALM DIS* Opens the relay alarm contacts, if closed, and prevents another relay

alarm closure from occurring.

ENA Enables activation of the minor alarm relay when a minor alarm condition

occurs.

Table continued on next page

TABLE 1. SYSTEM OPTION SETTINGS (CONTINUED)

Issue 1, Section 150-231-106

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Page 11

Mode Selection Description

DS1 AUTO The HLU and HRU independently monitor their incoming DS1 bit streams

for the B8ZS pattern. If either unit detects this pattern, it enters its B8ZS

mode. It reverts back to its AMI mode if no B8ZS patterns are received for

5 seconds.

B8ZS Places both the HLU & HRU into their B8ZS modes.

AMI* Places both the HLU & HRU into their AMI modes.

FRMG AUTO* Configures HiGain to operate in an auto-framing (AUTO) mode in which it

continuously searches the input T1 bit stream for a valid SF or ESF frame

pattern. This feature is required for fractional T1 applications (DS0

blocking) where it insures proper channel time slot alignment. While

HiGain can also process unframed data in this AUTO mode, it is

recommended that the UNFR mode be used for all unframed applications.

Using the AUTO mode for unframed applications runs the risk of

detecting “pseudo valid” frame sequences, which can affect the data

integrity.

UNFR Configures HiGain to operate in an unframed mode. This mode disables

the auto framing process and forces HiGain to function as a transparent

bit pipe.

HAIS 2LP* Causes HiGain to transmit the AIS signal at both the HLU & HRU T1

output ports when both of the HDSL loops are not in sync (LOSW).

1LP Causes HiGain to transmit the AIS signal at both the HLU & HRU T1

output ports when either of the two HDSL loops is not in sync (LOSW) or

if a minor alarm occurs.

SAIS ENA* Causes the List 6 and 7 HRU to transmit the AIS signal towards the NI

when in NREM or SMJK loopback.

DIS Causes the List 6 HRU to transmit the signal from the network towards the

NI and the List 7 to open and terminate its NI when in its NREM or SMJK

loopback states. The AIS signal is turned off.

CONF YES Confirms that all 12 of the above operating modes are to be updated to

their current choices.

NO* Prevents the most recently selected operating mode choices from being

updated. They remain as they were before the system option settings

mode was entered.

MARG 0 to 15 dB

(4*) The Margin Alarm Threshold can only be set via the RS-232 maintenance

port with a dumb terminal. See Figure 8. It determines the minimum

allowable margin below which a minor alarm will occur.

DS0 BLK/NONE* The DS0 blocking option can only be set via the RS-232 maintenance port

with a dumb terminal. See Figure 8. The 4 character HLU front panel only

displays the status of the blocking option. NONE indicates no channels

are blocked. BLK indicates at least one channel is blocked.

* Indicates HLU-231 factory settings. HiGain can be set to these default settings by pressing the SEL button for

6 seconds and then selecting the YES response to the resulting DFLT message.

Section 150-231-106

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8. LOOPBACK DESIGN DESCRIPTION

8.01 HiGain has a family of loopback options. The

most important of these is the Smart-Jack

loopback which enables the HRU-412 to respond to

the standard 2/3 in five Smart-Jack in-band loopback

codes and thus emulate the functions of a standard

NID. This option can be enabled or disabled from

either the front panel settings or the dumb terminal

system settings menu.

8.02 In addition to the Smart-Jack loopback,

HiGain can be configured for one of five

special in-band loopback command sequences. These

are selected from the SPLB user option shown in

Table 1 and Figure 8. The loopback locations are

shown in Figure 4.

8.03 GNLB is the HiGain Generic loopack code.

The GNLB allows in-band codes to loop-up

either the HLU/NLOC (4 in 7) or HRU/NREM (3 in 7)

towards the network. In addition, it allows in-band

codes to loop-up the HLU/CREM (6 in 7) or

HRU/CLOC (5 in 7) towards the customer. Either

loop-up condition is terminated (looped-down) with the

3 in 5 loop-down code. Both messages must be

present for five seconds before HiGain responds.

Table 2 list the test procedures that apply when using

the GNLB mode.

8.04 The A1LB loopback selection (Table 3)

complies with that proposed for HDSL

systems in the T1E1.4/92 recommendation with the

following additions:

1) Query loopback

2) IOR powerdown

3) Three loopback time-out choices

4) Initiation from either end

5) Repeating bit error signatures

6) Alternate Query loopback

These additions make A1LB identical to A2LB

described below. It is given a separate identity to

allow future T1E1 enhancements to be added without

affecting A2LB.

8.05 A2LB through A5LB are four special

addressable repeater loopback functions

which are supported by the List 6 version of HiGain.

These loopbacks provide HiGain with sophisticated

maintenance and trouble shooting tools. Tables 4

through 7 list the details of these Special Loopback

(SPLB) functions. A2LB & A5LB are patterned after

the Teltrend addressable T1 repeater loopbacks.

A3LB & A4LB are patterned after the Wescom

addressable T1 repeater loopbacks. All four SPLBs

have been enhanced to handle the specific

requirements of the following HiGain customers:

• A2LB (Teltrend) = Southwestern Bell

• A3LB (Wescom)=New England Tel.

• A4LB (Wescom Mod 1) =New York Tel.

• A5LB (Teltrend Mod 1) =Southern New

England Tel. (SNET)

8.06 A5LB differs from A2LB in that A5LB does not

block the arming code from exiting the HLU

into the network. A2LB can be configured to either

block this arming code after two seconds, and replace

it with the AIS code, or to unblock it by executing the

FAR-END ACTIVATE code. Since A5LB never

blocks the arming code from exiting the HLU, it does

not need this FAR-END ACTIVATE code. A3LB

differs from A4LB in that A3LB supports the

additional 1 in 6 Smart-Jack loopback command.

8.07 The HDU-451 doubler commands are only

available when using the HLU-231, List 6D

line unit which supports use of HiGain in-line HDSL

doublers. The simplest HiGain system includes two

loopback locations: The HLU and the HRU. The most

complex HiGain application includes the HLU, HRU &

two in-line HDU-451 doublers. Refer to the PairGain

HiGain Intelligent Repeater Application Note # 910

Part # 325-910-100 for more SPLB details.

8.08 When T1 loopback tests are performed on the

HiGain system with metallic loopback

connections at either end, the DS1 code that exists at

the metallic loopback interface may be different from

the DS1 code being received at the opposite end

when the DS1 user code is set to AUTO. This is

caused by the fact that in the AUTO DS1 code mode,

the HLU & HRU set their own code independent of

each other. Each end sets its transmit code to match

its receive code. Thus if one end is receiving AMI and

the other B8ZS, their codes are different. For

example, if the HRU has a metallic loopback and the

HLU’s receive pattern’s code is changed from AMI to

B8ZS and then the all 0 pattern is sent into the HLU,

the HLU changes to its B8ZS mode while the HRU

remains in its AMI mode and thus loops all 0’s. This

causes the HRU to indicate a LOS condition which

then causes the HLU to output the AIS pattern.

8.09 HiGain may take longer than normal to

respond to inband loopback commands when

its framing mode is set to UNFR and the inband

commands are sent in either an SF or ESF mode.

The frame bits override the command bits and cause

errors in the command sequence. These errors cause

HiGain to reject some sequences. This can extend the

detection interval.

Issue 1, Section 150-231-106

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Page 13

Figure 4. HLU-231 Loopback Configurations. The most important of the HiGain family of loopback options is the Smart-Jack

loopback, which emulates the functions of a standard NID.

Section 150-231-106

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C. INSTALLATION AND TEST

9. INSTALLATION OPTIONS

9.01 Upon receipt of the equipment, 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.

9.02 The HLU-231 is designed to mount in a 220-

type ORB shelf or equivalent SXSS, Kentrox

T-Term and Wescom 342-30 shelves. The HLU-231

slot pin-outs are shown in Figure 5.

Figure 5. HLU-231, List 6 Pin-Outs. The active pins are highlighted in black in the above illustration.

Issue 1, Section 150-231-106

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10. TESTING PROCEDURES

10.01 Tables 2 through 7 provide step-by-step test

procedures for the HLU-231 unit as a function

of the loopback option selected. These procedures

allow verification of the integrity of the HDSL channels

to the HRU-412 remote unit as well as the DS1

channels to the customer and the local DSX-1

interface.

10.02 The HLU’s 4 character front panel display has

many useful system diagnostic messages.

They are listed in Tables 8 & 9. This display turns on

when power is initially applied to the 231. In order to

conserve power, it only remains on for five minutes if

neither the MODE nor SEL buttons are depressed.

The use of either button restarts the 5-minute power-

control timer.

10.03 If trouble is encountered on the DSX-1

interface, verify that the unit is making a

positive connection with the mounting assembly’s

connector. Also, verify that the pre-equalizer is

properly set. All installations should be set to the

largest value that does not exceed the distance from

the DSX-1 to the shelf.

10.04 The transmit and receive T1 DSX-1 ports

have splitting access and bridging miniature

210 jacks. Connecting one cable between the two

BDG jacks and another between the two SPAN jacks

splits the XMT and RCV and creates metallic

loopbacks towards both the DSX-1 and the HLU.

10.05 Figure 7 shows the HLU status screen. It

contains useful information on both HDSL

loops and the DS1 input. Figures 10, 11 and 12 show

the Performance Data and Alarm History screens. All

the performance data shown in Figures 10, 11 and 12

can be cleared to zero by selecting the (C)lear option

from the HLU Status Screen shown in Figure 7. Note

that since the HLU is considered the master module,

this clears all performance data screens at both the

HLU & the HRU. Clearing the data from the HRU only

clears performance data at the HRU, not at the HLU.

TABLE 2. TEST PROCEDURES FOR GNLB OPTION

Step Action

1 Have the CO tester send the HRU (3 in 7) in-band loop-up code for 5 seconds. Observe that the

HLU displays the “NREM” message indicating an HRU loopback is in effect (see Figure 4).

2 Have the CO tester transmit a T1 test signal into the HLU and verify that the returned (looped)

signal is error free.

3 If the above test fails, have the CO tester transmit the (3 in 5) in-band loop-down code. Verify that

the HLU display returns to normal.

4 Have the CO tester send the HLU (4 in 7) in-band loop-up for 5 seconds. Observe that the HLU

displays the “NLOC” message indicating an HLU loopback is in effect.

5 Repeat step “2”. If the test passes, the problem is in the cable pair or the HRU. If it fails, the

problem is in the CO equipment.

6 The NREM and NLOC loopbacks can also be initiated from the front panel of the HLU with the

MODE and SEL pushbuttons. See Paragraph 6.23 for details.

7 The HLU can be looped-up from the remote location (CREM) by issuing the 6 in 7 command at the

HRU’s DS1 input port.

8 The HRU can be looped-up from the remote location (CLOC) by issuing the 5 in 7 command at the

HRU’s DS1 input port.

Section 150-231-106

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TABLE 3. TEST PROCEDURES FOR A1LB OPTION

Step Action

1 Send into the HLU the inband ARMING and NIU (Network Interface Unit) LPBK code 11000

for at least 5 seconds, or at least 4 repetitions of the 16-bit ESF Data Link ARMING code 0001

0010 1111 1111.

2 Monitor the output of the HLU-231 for the return of the pattern. Return of pattern indicates that

either the HRU has looped-up (if the SMART-JACK LOOPBACK option is ENABLED) or that

an external NIU has looped up (if the SMART-JACK LOOPBACK option is DISABLED) and

that the HLU and HRU units have been ARMED. Verify that the HLU display intermittently

indicates “ARM” and also “SMJK” if the HRU is in loopback. Also verify, if possible, that the

LOOPBACK LED of the HRU-412 is flashing, indicating that the HRU is armed or that it is on

solid, indicating that it is both armed and in loopback.

3 Once armed, the HLU can be looped back (NLOC in Figure 4) by sending IOR (Intelligent

Office Repeater) LPBK activation code 1101 0011 1101 0011 for at least 5 seconds. The

tester observes the following activation response:

• 2 seconds of AIS (all ones), followed by:

• 5 seconds of returning data pattern, followed by:

• 231 logic errors (including the frame bits) occur in the returned pattern (10 errors if ILR-1

were sent), followed by:

• normal looped data. (Note that this error pattern will repeat every 20 seconds as long as

the IOR loopback pattern is being sent. This same 20 second repeat scenario also applies

to ILR, Time-Out Override and Query commands.)

The HiGain Line Unit is now in Logic Loopback (NLOC of Figure 4). The display on the HLU-

231 periodically shows “NLOC” (network local loop) and “ARM” (the HLU is still armed) in

addition to the margin displays. The Loopback Time-out option, which is user settable to

NONE, 20, 60 or 120 minutes, determines the duration of this loopback unless it is overridden

by the TIME-OUT OVERRIDE command or a loop down command is sent. If the Time-out

Override code 1101 0101 1101 0110 is received, the “activation sequence” described above is

repeated and the automatic timed expiration of the loopback is inhibited. If this Time-out

Override is sent, then the only way to loop the HLU down is to issue the IR (Intelligent

Repeater) LPDN (loopdown) code 1001 0011 1001 0011 or to issue the NIU (Network

Interface Unit) LPDN and Disarm code 11100. The automatic time-out timer is restored during

subsequent loopback sessions.

4 Upon completion, the tester sends IOR LPDN code 1001 0011 1001 0011 to loop-down the

HiGain Line Unit. The unit remains armed however, as indicated by the “ARM” message on

the HLU-231 and the flashing of the HRU-412’s LOOPBACK LED.

Table continued on next page

Issue 1, Section 150-231-106

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TABLE 3. TEST PROCEDURES FOR A1LB OPTION (CONTINUED)

Step Action

5 Using the following codes, a network tester can activate loopbacks NLOC or NREM or SMJK

(if enabled) shown in Figure 4. A customer tester can activate loopbacks CLOC or CREM.

ADDRESSABLE 1 (A1LB) REPEATER LOOPBACK COMMANDS

ARMING or NIU LPBK (inband) Arming code 11000 11000..

ARMING or NIU LPBK (ESF Data

Link) Arming code 1111(F)*1111(F)0100(4)1000(8)

IR LPDN or DISARM (inband) Disarming

code 11100 11100..

DISARM (ESF Data Link) Disarming

code 1111(F)1111(F)0010(2)0100(4)

IOR LPBK (NLOC & CREM 231

errors) HLU Loop up 1101(D)0011(3)1101(D)0011(3)

ILR-2 LPBK (NREM & CLOC 20 bit

errors) HRU Loop up 1100(C)0111(7)0100(4)0010(2)

IR LPDN Loop down

(HLU or HRU) 1001(9)0011(3)1001(9)0011(3)

IR QUERY LPBK Query

loopback 1101(D)0101(5)1101(D)0101(5)

IR ALTERNATE QUERY LPBK Alternate

Query

loopback

1101(D)0101(5)1110(E)1010(A)

TIME-OUT OVERRIDE Loopback

Time- out

Override

1101(D)0101(5)1101(D)0110(6)

FAR END NIU ACTIVATE Unblock AIS

& pass 2 in 5 1100(C)0101(5)0101(5)0100(4)

IOR POWER DOWN (HLU) Removes

HDSL line

power

0110(6)0111(7)0110(6)0111(7)

Note: The left most bit arrives first in all sequences. The detection algorithm functions reliably

with a random 10E-3 bit error ratio (BER) on the facility. The IOR POWER DOWN code must

remain present for the duration of the power down mode. When this code is removed, HiGain

returns to its normal unlooped and unarmed state. *This is the HEX number for the 4 bit group.

6 After testing is complete, send the universal loopdown [IR (Intelligent Repeater) LPDN] code if

the system is to loopdown but remain ARMED. Send the disarm code 11100 if all the

equipment is to be looped down, disarmed and returned to normal operation. Note that the

ARMED mode has an automatic time-out of 120 minutes.

7 The NREM and NLOC loopbacks can also be initiated from the front panel of the HLU with the

MODE and SEL pushbuttons. See Paragraph 6.23 for details.

Section 150-231-106

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TABLE 4. TEST PROCEDURES FOR A2LB OPTION

Step Action

1 Send into the HLU the inband ARMING and NIU (Network Interface Unit) LPBK code 11000

for at least 5 seconds, or at least 4 repetitions of the 16-bit ESF Data Link ARMING code 0001

0010 1111 1111.

2 Monitor the output of the HLU-231 for the return of the pattern. Return of pattern indicates that

either the HRU has looped-up (if the SMART-JACK LOOPBACK option is ENABLED) or that

an external NIU has looped up (if the SMART-JACK LOOPBACK option is DISABLED) and

that the HLU and HRU units have been ARMED. Verify that the HLU display intermittently

indicates “ARM” and also “SMJK” if the HRU is in loopback. Also verify, if possible, that the

LOOPBACK LED of the HRU-412 is flashing, indicating that the HRU is armed or that it is on

solid, indicating that it is both armed and in loopback.

3 Once armed, the HLU can be looped back (NLOC in Figure 4) by sending IOR (Intelligent

Office Repeater) LPBK activation code 1101 0011 1101 0011 for at least 5 seconds. The

tester observes the following activation response:

• 2 seconds of AIS (all ones), followed by:

• 5 seconds of returning data pattern, followed by:

• 231 logic errors (including the frame bits) occur in the returned pattern (10 errors if ILR-1

were sent), followed by:

• normal looped data. (Note that this error pattern will repeat every 20 seconds as long as

the IOR loopback pattern is being sent. This same 20 second repeat scenario also applies

to ILR, Time-Out Override and Query commands.)

The HiGain Line Unit is now in Logic Loopback (NLOC of Figure 5). The display on the HLU-