PairGain HLU-319 User manual

PAIRGAIN TECHNOLOGIES Section 150-319-124
Technical Practice Revision 03
Engineering - PLANT Series November 6, 1996
Page 1
PAIRGAIN TECHNOLOGIES HIGAINTM LINE UNIT
MODEL HLU-319
List 2D, PairGain #150-1140-24, CLEI Code: T1L1BH03AA
CONTENTS PAGE
A. PRODUCT OVERVIEW
(Doubler and Non-Doubler)
1. DESCRIPTION AND FEATURES 2
2. HIGAIN SYSTEM APPLICATIONS 2
3. FUNCTIONAL OPERATION 3
4. ALARMS 5
5. SYSTEM OPTIONS 7
6. HDSL LINE VOLTAGE OPTION 11
7. INSTALLATION 12
8. SPECIFICATIONS 12
9. CERTIFICATION 12
10. WARRANTY 13
11. TECHNICAL ASSISTANCE 13
B. APPLICATIONS WITHOUT HIGAIN
DOUBLERS (HDU-451)
12. SECTION INTRODUCTION 14
13. POWER CONSUMPTION 14
14. LOOPBACK OPERATION 14
15. TESTING 16
16. SYSTEM MAINTENANCE MENU
SCREENS 29
C. APPLICATIONS USING HIGAIN DOUBLERS
(HDU-451)
17. DOUBLER DEPLOYMENT RULES 37
18. POWER CONSUMPTION 37
19. LOOPBACK OPERATION 38
20. TESTING 40
21. SYSTEM MAINTENANCE MENU
SCREENS 51
Figure 1. HLU-319, List 2D Front Panel. The PairGain
HLU-319 is the local unit used in conjunction with the HRU-
412 remote unit to provide a complete HiGain HDSL
system.
CAUTION
This product incorporates static sensitive
components. Proper electrostatic discharge
procedures must be followed.

Section 150-319-124
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A. PRODUCT OVERVIEW
(Doubler and Non-Doubler)
1. DESCRIPTION AND FEATURES
1.01 PairGain’s HiGain Line Unit Model HLU-319
Issue 1, List 2D (see Figure 1) is the Central Office
side of a repeaterless T1 transmission system. When
used in conjunction with an HRU-412 HiGain Remote
Unit, the system provides 1.544 Mbps transmission on
two unconditioned copper pairs over the full Carrier
Serving Area (CSA) range. The CSA includes loops
which are up to 12,000 feet of AWG 24 or 9,000 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 The HLU-319 is compatible with the following
T1 repeater shelves and associated equipment:
• Charles Ind. #3192 (28-slot connectorized)
• Charles Ind. #3192-9F Alarm Card
• Larus #1185 (28-slot connectorized)
• Larus #1184 Alarm Card
• Charles Ind. #3192-WR (28-slot wire wrap)
• Charles Ind. #343-00
(12- to 14-slot wire wrap)
• Charles Ind. #319-02 (22-slot
connectorized)
• Charles Ind. #319-04 (22-slot wire wrap)
• Charles Ind. #340-00
(9- to 11-slot wire wrap)
• PairGain HMS-318 (22-slot, 19-inch shelf)
• PairGain HHS-319 (3-slot, 19-inch
horizontal shelf)
• PairGain HMS-317 (28-slot, 23-inch shelf)
• PairGain HMS-308
(8-slot remote enclosure)
1.03 The Charles Ind. #343-00 and #340-00
shelves do not support the HLU-319’s Minor Alarm
output on pin H. Also, if slots 1 and 2 of these
shelves were wired for the 3408 Fault Locate unit,
they must be rewired to accept the HLU-319.
1.04 Revision History of this practice.
Revision 03—November 6, 1996
a) Added reference to the HDU-451 List 4
and HDU-439/437 doublers.
1.05 HLU-319, List 2D features:
• Selectable DS-1 pre-equalizer
• 130 to 200 Vdc HDSL line power for
doubler and HRU-412
• Optional bipolar (± 65 or ± 100 Vdc) or
unipolar (-130 or -200 Vdc) HDSL line
power voltage via switch S2
• Front panel HDSL S/N margin display
• Compatible with Span Terminating Shelf
(STS) high density shelves
• Selectable loopback activation codes
• RS-232 maintenance port
• Network Management Administration
(NMA) interface
• Non-volatile front panel operator setup
• Front panel DS1 splitting and bridge 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
• HDSL AIS and Smart-Jack AIS options
• Easy return to factory default user settings
• Circuit ID option
• Low power consumption
• 30% less power than List 1
2. HIGAIN SYSTEM APPLICATIONS
2.01 The HiGain system 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
ohms 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. The
HiGain system also provides a means of quickly

Section 150-319-124
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deploying service in advance of fiber-optic
transmission systems. With the HiGain system,
service can be provided within hours. Fiber optic
systems can be installed at a leisurely pace and cut
over from the installed HiGain system when
convenient to do so. The installed HiGain system can
then be easily removed and utilized elsewhere.
3. FUNCTIONAL OPERATION
3.01 The HiGain system utilizes PairGain 2-Bit
1-Quartenary (2B1Q) HDSL transceiver systems to
establish two full duplex 784 kbps data channels
between the HLU-319, List 2D and a remotely
mounted HRU-412 HiGain Remote Unit. This
provides a total capacity of 1.568 Mbps between the
two units.
3.02 A block diagram of the HLU-319, List 2D is
shown in Figure 2. The HiGain HLU-319, List 2D
receives a 1.544 Mbps DS1 data stream from the
DSX-1 digital cross connect interface. The HLU-319,
List 2D contains a DSX-1 frame synchronizer
controlled by an 8-bit microprocessor that determines
the type of framing on the DS1 stream and
synchronizes to it. The HLU-319, List 2D recognizes
Super Frame (SF) (including D4) or Extended Super
Frame (ESF) framing. When the data is unframed,
the HLU-319, List 2D arbitrarily defines a frame bit.
3.03 The HLU-319, List 2D contains a multiplexer
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 DSX-1 payload. The DSX-1
stream is separated into two parallel streams that
comprise the payloads of the HDSL channels. The
HLU-319, List 2D allocates the DS0 time slots
according to the version of HRU-412 to which it is
connected. Older version HRUs require the odd DS0
time slots allocated to loop 1 and the even DS0 time
slots to loop 2. Newer versions allocated DS0 time
slots 1 through 12 to loop 1, and time slots 13 through
24 to loop 2. The 8 kbps frame bits of the DSX-1
stream are included on both HDSL channels. The two
formatted HDSL channels are passed to the HDSL
transceivers which convert them to the 2B1Q format
on the HDSL lines. The 2B1Q line code is designed
to operate in a full-duplex mode on unconditioned
pairs. The transceiver 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. HLU-319, List 2D 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.

Section 150-319-124
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3.04 The received HDSL channels are processed
by the transceiver and then passed on to the HLU-
319, List 2D demultiplexer module. The demultiplexer
provides frame synchronization for each of the two
HDSL loops. The demultiplexer and HDSL
transceivers work under control of the HLU-319, List
2D microprocessor and compensate for data
inversions caused by tip-ring reversals and loop
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 Frame
Sync Word (FSW) of each loop, the demultiplexer can
reconstruct the original 1.544 Mbps DS1 stream from
the payloads of the two HDSL loops. The CRC fields
on the HDSL streams allow the HLU-319, List 2D to
determine if errors are present on the channel due to
excessive impairments on the HDSL pairs or
excessive impulse or crosstalk noise.
3.05 The demultiplexer removes data link
messages from the HDSL loops and passes them to
the microprocessor. This mechanism allows
operations messages and status to be exchanged
between the HLU-319, List 2D and the HRU-412
remote unit.
3.06 The reconstructed HDSL data is buffered in a
first-in-first-out (FIFO) buffer within the demultiplexer.
A frequency synthesizer, in conjunction with the FIFO,
regulates the output bit rate and reconstructs the
DSX-1 clock at the exact rate received from the
remote end. The HiGain system operates at T1 rates
of 1.544 Mbps with up to ± 200 bps of offset.
3.07 A DSX-1 interface driver converts the input
data to an Alternate Mark Inversion (AMI) or Binary
Eight Zero Substitution (B8ZS) format. The DSX-1
equalizer is programmable to five different lengths, as
determined by the distance between the HLU-319,
List 2D and the DSX-1 interface. This provides CB-
119 specification compliant pulses at the DSX-1
interface over a range of 0 to 655 feet of ABAM-
specification cable.
3.08. The HLU-319, List 2D contains two separate
power converters. The main power supply converts
-48 Vdc local battery to logic power for the HLU-319,
List 2D circuits. The line power supply converts the
-48 Vdc battery to either 130 Vdc (for non-doubler
applications) or 200 Vdc (for doubler applications),
then provides simplex power feed on the two HDSL
line interfaces. Switch S2 allows the user to configure
the HDSL line powering voltage to be unipolar (0 to
-130 V and 0 to -200 V) or bipolar (± 65 V and ± 100
V) (see Figure 5.) The line power supply can be
turned on or off by the microprocessor and is
automatically shut down in the presence of line short
circuits or microprocessor failure.
3.09 A female 9-pin (DB-9) RS-232 connector is
provided on the front panel (see Figure 3). This
connector provides asynchronous access to the
HiGain system maintenance provisioning and
performance monitoring firmware. The port is
configured as DCE with 8 data bits, 1 stop bit and no
parity. Operator interaction with the firmware is via an
ASCII terminal or a Personal Computer with
asynchronous communication software. Striking the
Space bar several times enables the HLU-319, List
2D to automatically match the terminal line baud rate,
from 1200 to 9600 baud. Figure 7 through Figure 14
show the menu selections available from the terminal
for non-doubler applications. Figure 16 through
Figure 34 show the menu selections available from
the terminal for doubler applications. Table 8 defines
the terms used in the non-doubler System Status
screen. Table 18 defines the terms for the doubler
System Status screens.

Section 150-319-124
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4. ALARMS
4.01 Pin H is the HLU-319 minor alarm (MNRALM)
output pin, which replaces the Local Loss of Signal
alarm on normal High Density (3192) repeaters. Its
normally floating output can connect to pin 1 of the
1184 or 3192-9F Alarm Card in position 29 of the High
Density (HD) shelf. This pin must never be taken
above +5 V or below -60 V. The HLU-319 forces pin
H to +5V (maximum of 10 mA) for any of the
conditions listed below. (The accompanying front
panel message is listed below in bold letters.) More
than one alarm condition can exist at any given time,
but only one message can be displayed. For multiple
alarms, only the highest priority alarm is displayed.
The alarms are listed in their order of priority:
1. ALRM LOSW: Either HDSL loop lost sync
2. ALRM LLOS: Loss of HLU DSX-1 input
signal
3. ALRM RLOS: Loss of HRU DSX-1 input
signal
4. ALRM TLOS: A user option that causes
the loss of the HRU DS1 input from the CI
to initiate a logic loopback in the HRU.
5. ALRM H1ES: HDSL loop 1 has exceeded
the 24-hour user-selected Errored Seconds
CRC threshold. If both H1ES and H2ES
occur, only H1ES is displayed on the front
panel.
6. ALRM H2ES: HDSL loop 2 has exceeded
the 24-hour user-selected Errored Seconds
CRC threshold. If both H1ES and H2ES
occur, only H1ES is displayed on the front
panel.
7. ALRM DS1: The total number of bipolar
violations (BPV), at either the HLU or the
HRU DS1 inputs, have exceeded the 24-
hour user-selected threshold.
8. ALRM MAL1: The margin on HDSL loop
1 has dropped below the minimum
threshold value set by the RS-232 terminal
Margin Alarm Threshold; as described in
Section 5.
9. ALRM MAL2: The margin on HDSL loop
2 has dropped below the minimum
threshold value set by the RS-232 terminal
Margin Alarm Threshold; as described in
Section 5.
4.02 Pin H, MNRALM, remains at +5V for the
duration of the alarm condition. If the Wescom 1184
Alarm Card is installed in the shelf, its LOS LED lights
for every MNRALM. The HLU-319’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 5 for System
Settings information). The MAL(X) alarm can be
DISabled by setting the margin alarm threshold to 0.
The minor alarm can be retired by executing the
Alarm CutOff (ACO) option. This is accomplished by
pressing the SEL button on the front panel. This turns
the alarm off and replaces the ALRM message with
the ACO message. However, 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.
Disabling the ALM also retires an ACO condition.
4.03 Setting the ALM option to DIS(able) only
prevents the minor alarm output alarm bus on pin H
from being activated on a minor alarm event. The
Status LED still flashes red and the ALRM message is
still displayed.
4.04 The HLU-319 Pin 10, Fuse Alarm is driven to
-48 V whenever its on-board fuse opens. It emulates
the function of the Fuse Alarm output from Pin 10 of
normal HD repeaters. The Pin 10 signal is connected
to Pin 5 of the 1184 Alarm Card (slot 1 in HD shelf)
and causes the 1184 Fuse ALM LED to light when the
Pin 10 signal is activated. Its normally floating output
must never be driven above ground or below -80 V. It
can sink a current of 10 mA.
4.05 Pin 7 is the NMA serial bus. It is provided for
access to the HMU-319 shelf controller card that will
provide shelf management. Whenever the HLU-319 is
under management, it periodically displays the MNGD
message on its 4 character front panel LED display.
Some of the features of the HLU-319 are affected
when it is under management. Consult the
management units practice for more detail.
4.06 The HLU-319 does not support the BPV
function (Pin E) of normal HD repeaters.
4.07 The HLU-319’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 Section A Paragraph 4.02)
• RED - Fuse Alarm
• YELLOW - Self-test in process or an HLU
Loopback in effect (CREM or NLOC)
• FLASHING YELLOW - HLU in Armed state

Section 150-319-124
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Figure 3. DB-9 RS-232 I/O Pin-Outs. A standard RS-232 (DB-9, female) connector on the front panel provides access to the
menu interface feature via a RS-232 terminal.
Figure 4. HLU-319, List 2D Card-Edge Connectors. The active pins are highlighted in black in the above illustration.

Section 150-319-124
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5. SYSTEM OPTIONS
5.01 The HLU-319, List 2D contains a non-volatile
RAM (NVRAM) which stores the system options
settings. No dip-switches or jumpers are required to
configure these system options. They are set via
push buttons on the front panel or through the RS-232
interface or from the Network Management interface.
The System Settings are retained if shelf power is lost
or if the HLU-319, List 2D is unplugged. Table 1 lists
the HLU-319, List 2D System Options. Figure 10 and
Figure 22 illustrate the same options on the HLU-319,
List 2D non-doubler and doubler System Settings
Menu screens, respectively. In the System Settings
Menu (which is identical for both non-doubler and
doubler applications), the settings shown represent
the factory default settings.
5.02 The Setup momentary push buttons (Mode
and SEL) are used to set the options from the HLU-
319, List 2D front panel. To initiate the Options
Setting mode, press the Mode button, for at least one
second, but less than three seconds, and release.
The message displayed on the front panel alternates
between the first system parameter and its current
setting. Pressing the SEL button scrolls the display
(one at a time) through all possible settings of the
parameter being displayed. After the desired setting
has been selected, press the Mode button. This
updates the currently displayed mode to the selected
setting, then selects the next configurable parameter.
After the last parameter has been selected, the
display shows “CONF NO (Confirm? (Yes/No)).” If
the Mode button is pressed at this time, none of the
changed parameters are installed. If the SEL button
is pressed, a “YES” message is displayed, and the
selected 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, after 30 seconds, neither button is
pressed.
5.03 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 Default 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.
5.04 Pressing the Mode button for three or more
seconds causes the display to scroll through the HLU-
319, List 2D software version number, its list number,
the type of frame pattern being received from the
DSX-1, the line code setting of the HLU-319, List 2D,
and all 14 options settings. The line code parameter
is the actual DS1 line code being received by the
HLU-319, List 2D when the DS1 code pattern is set to
Auto. Otherwise, the line code parameter mimics
either of the other two line code settings, AMI or
B8ZS, and is not determined by the received line
code.
5.05 The DS1 line code option should always be
set to conform to the type of T1 service (AMI or
B8ZS) being provided by the HiGain system. The
Auto mode, which can adapt to either AMI or B8ZS,
should only be used in applications that require it
(such as when HiGain acts as a standby circuit to T1
circuits whose line codes are not known or may be
both AMI and B8ZS), because it has the following two
limitations:
1. The Auto mode induces one BPV in the T1
bit stream whenever it switches from AMI
to B8ZS.
2. The Auto mode allows each HiGain end
(HLU and HRU) to set its DS1 mode to the
code it is receiving at its local T1 input
port. This makes each unit’s code
independent of the T1 code, which is sent
from the distant T1 input port. Thus, if the
line codes being received by HiGain are
different in each of the two T1 directions,
the HiGain T1 output codes will not match
their respective T1 input codes at the other
end. This could cause the customer’s
received data to be AMI instead of B8ZS,
and thus violate the one’s density rules by
having excessive zeroes.
5.06 The following three user options can only be
set via the RS-232 terminal interface: Circuit ID, DS0
Blocking, and Margin Alarm Threshold.

Section 150-319-124
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5.07 The Circuit ID option is set by choosing the
Hoption from the terminal Main Menu screen (see
Figure 7 for non-doubler applications and Figure 16
for doubler applications). The message “ENTER
CIRCUIT ID#:” (24 characters max) follows the “H”
selection. Press Enter after entering the chosen set
of alpha-numeric ID characters; choose Cto confirm.
Note that 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-319, List 2D
screens, as shown in Figures 7 through 14 for non-
doubler applications and Figures 16 through 34 for
doubler applications. The ID does not appear on the
HRU-412 screens when the maintenance port is
accessed at the remote unit. Note that the Circuit ID
can not be set to its factory setting (all blanks) setting
when the DFLT setting option is utilized (see Section
A Paragraph 5.03).
5.08 To set the DS0 Blocking option, from the Main
Menu screen, press Cto select the System Settings
Menu screen. The menu shown in Figure 10 (for non-
doubler applications) and Figure 22 (for doubler
applications) appears. Press B, as shown in
parentheses of the DS0 blocking selection. The DS0
channels are blocked or unblocked by entering each
channel number. Multiple channels can be selected
by inserting a space between each entry. After all the
new settings have been made, press E(“Exit”) and C
(“Confirm”). The new choices are now installed. Also,
all blocked channels are temporarily “unblocked” for
all HiGain system loopback tests. This allows the
standard full bandwidth T1 loopback tests to be
performed.
5.09 To set the Margin Alarm Threshold, select G
from the System Settings Menu screen. Enter the
desired minimum acceptable alarm threshold from the
0 to 15 dB range. This causes a minor alarm to occur
if either the margin on HDSL loop 1 (MAL1) or loop 2
(MAL2) of any span drops
below
the selected
threshold value (see Section 4). Since the margin can
never drop below 0, choosing 0for the margin
threshold turns the margin alarm off.
5.10 Other system settings are set by using a
terminal in a similar manner. Enter the key
represented by the letter in parentheses of the
parameter to be changed. Each entry of this letter
scrolls the parameter to its next value. Hit the Enter
key after making each selection. After all selections
have been made, press Eto “Exit” and Cto “Confirm”
the changes. This activates the new choices and
returns control to the Main Menu screen.
5.11 The new T1 transceiver chip in the List 2D
allows the unit to process both B8ZS and AMI code
inputs, regardless of the DS1 code setting (AMI or
B8ZS). Earlier units caused input BPV, if B8ZS
patterns were processed while in the AMI mode.
When the newer units are in the AMI mode, they can
receive B8ZS but can only transmit AMI. For this
reason, mixed systems (those consisting of both HLU-
319, List 2D and older Lists 1, 2, 3, 3A and 4 HRU-
412 units) will respond differently in each direction for
B8ZS inputs when in their AMI modes.
5.12 The Self-test mode, which 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 Alarm
Indicating Signal (AIS) pattern, which is normally
transmitted from the HLU-319, List 2D during these
out-of-sync intervals, to exhibit occasional BPVs.
5.13 The HAIS option provides two selections (1LP
and 2LP) for the T1 transmit outputs at both the HLU-
319, List 2D and HRU-412 for HDSL loss-of-sync
conditions. The “1LP” selection causes the AIS
pattern to be transmitted at both T1 outputs when
either of the two HDSL loops experience a loss-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 allows both down and
upstream equipment to be made aware of the loss of
one HDSL loop or a loop with low margin. The 1LP
selection 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 from 5 to 10 dB. Thus, if
the margin alarm is set to 5 dB below the normal
margin at turn-up, when one conductor opens, a minor
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.
5.14 All user options that affect the operation in
both the HLU-319, List 2D and HRU-412, (such as
HAIS, SAIS and DS0 blocking) are not available in
older versions of the HRU-412, Lists 1, 2, 3, 3A, and 4
that do not support these newer options.

Section 150-319-124
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TABLE 1. HLU-319, LIST 2D SYSTEM OPTIONS
Note:
An asterisk (*) indicates HLU-319, List 2D factory (default) settings.
Mode Selection Description
EQL 0* Sets the equalizer to DSX-1 for 0 to 132 feet.
133 Sets the equalizer to DSX-1 for 133 to 265 feet.
266 Sets the equalizer to DSX-1 for 266 to 398 feet.
399 Sets the equalizer to DSX-1 for 399 to 532 feet.
533 Sets the equalizer to DSX-1 for 533 to 655 feet.
LPBK DIS Configures the HiGain system to ignore the (2 in 5) in-band Smart-Jack loopback command.
ENA* Enables the HiGain system to recognize the (2 in 5) in-band Smart-Jack loopback
command.
SPLB GNLB* Configures the HiGain system to respond to the generic (3/4/5/6 in 7) in-band loopback
codes.
A1LB and
A2LB Configures the HiGain system to respond to the Teltrend addressable repeater in-band loopback codes.
A3LB Configures the HiGain system to respond to the Wescom addressable repeater in-band
loopback codes.
A4LB Configures the HiGain system to respond to the Wescom Mod 1 addressable repeater
in-band loopback codes.
A5LB Configures the HiGain system to respond to the Teltrend Mod 1 addressable repeater
in-band loopback codes.
PWRF DIS Disables powering to the HRU-412 and doubler.
ENA* Enables powering to the HRU-412 and doubler.
ZBTS ON Tells the HiGain system that the ESF frame is operating in its Zero Byte Time Slot Interface
(ZBTSI) mode.
OFF* Tells the HiGain system that the ESF frame is operating in its normal non-ZBTSI mode.
ESAL 17 Flashes the red Status LED when 17 Errored Seconds (ES) (17 HDSL cyclic redundancy
check (CRC) errors on either HDSL loop or a total of 17 BPVs) occur within a 24-hour
period.
170 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* Disables the activation the output alarm has on pin H when a minor alarm occurs.
ENA Enables the activation the output alarm has on pin H when a minor alarm occurs.
Table continued on next page

Section 150-319-124
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TABLE 1. HLU-319, LIST 2D SYSTEM OPTIONS (CONTINUED)
Mode Selection Description
DS1 AUTO The HLU-319, List 2D and HRU-412 independently monitor their incoming T1 bit streams
for the Binary Eight Zero Substitution (B8ZS) pattern. If either unit detects this pattern, it
enters its B8ZS mode. It reverts back to its Alternate Mark Inversion (AMI) mode if no
B8ZS patterns are received for five seconds.
B8ZS Places both the HLU-319, List 2D and HRU-412 into their B8ZS modes.
AMI* Places both the HLU-319, List 2D and HRU-412 into their AMI modes.
FRMG AUTO* Configures the HiGain system 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 the HiGain system can also process unframed data in
this Auto mode, it is recommended that the unframed (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 the HiGain system to operate in an unframed mode. This mode disables the
auto framing process and forces the HiGain system to function as a transparent bit pipe.
HAIS 2LP* Causes the HiGain system to transmit the AIS signal at both the HLU-319, List 2D and
HRU-412 T1 output ports when both of the HDSL loops are not in-sync (LOSW).
1LP Causes the HiGain system to transmit the AIS signal at both the HLU-319, List 2D and
HRU-412 T1 output ports when either of the two HDSL loops is not in-sync (LOSW) or if a
MARGin alarm occurs.
SAIS ENA* Causes the Lists 6 and 7, HRU-412 to transmit the AIS signal toward the Customer
Interface (CI) when in NREM or Smart-Jack loopback (see Figure 6).
DIS Causes the List 6, HRU-412 to transmit the signal from the network toward the CI when
an HRU NREM or Smart-Jack loopback is executed. The AIS signal is off.
CONF YES Confirms that all twelve operating modes (listed above) are to be updated to their current
selections.
NO* Prevents the most recently selected operating mode selections from being updated. They
remain as they were before the system options settings mode was entered.
MARG 0 to 15 dB The Margin Alarm Threshold can only be set, via the RS-232 maintenance port, with a
terminal (see Figures 10 and 22 for non-doubler and doubler screens, respectively). It
determines the minimum allowable margin below which a minor alarm can occur. Note
that setting the threshold to “0” inhibits the margin alarm.
4 dB* (Default value)
DS0 BLK The DS0 blocking option can only be set via the RS-232 maintenance port with a terminal
(see Figures 10 and 22 for non-doubler and doubler screens, respectively). The
4-character HLU-319, List 2D front panel LED readout only displays the status of the
blocking option. BLK indicates at least one channel is blocked.
NONE* “None” indicates no channels are blocked.

Section 150-319-124
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6. HDSL LINE VOLTAGE OPTION
6.01 The symmetry of the HDSL line powering
voltage can be set by the S2 switch, located on the
printed circuit board, as shown in Figure 5.
6.02 The factory default setting is unipolar (-). It
sets the HDSL line voltage to 0 V on loop 2 and to
either -130 V (for non-doubler applications) or -200 V
(for doubler applications) on loop 1. This setting
keeps the HDSL cable pair voltage at or below ground
potential, thereby avoiding corrosion problems caused
by cable voltages more positive than ground.
6.03 The bipolar selection sets the HDSL line
voltage to +65 V on loop 2 and -65 V on loop 1, for
non-doubler applications. Doubler applications will
have +100 V on loop 2 and -100 V on loop 1. This
setting reduces the maximum ground referenced
voltage to 100 V, but applies positive voltage to the
cable pairs, which could accelerate corrosion on the
cable pairs.
6.04 The line voltage power supply, used for both
options, is ground referenced, but also ground isolated
by 200 kohms. This ground isolation reduces
problems due to induced noise currents and large
surge voltages, which are ground referenced. It also
reduces ground fault currents, which improves the
product’s safety. The safety issue thus depends
solely on the differential voltage across loop 1 and
loop 2, and is independent of S2’s setting.
Figure 5. HDSL Line Voltage Switch S2

Section 150-319-124
Revision 03
Page 12
7. INSTALLATION
7.01 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 Technologies.
7.02 The HLU-319 mounts in the group of both
wire-wrapped and connectorized shelves listed in
Section A Paragraph 1.02. The HLU-319 slot pins are
shown in Figure 4.
8. SPECIFICATIONS
HDSL Line Code
784 kbps 2B1Q
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 Start-up Time
30 seconds (typical), 60 seconds (maximum) per span
One-way DS1 Delay
<220 microseconds per span
DSX-1 Line Impedance
100 ohms
DSX-1 Pulse Output
Pre-equalized for 0 to 655 feet of ABAM-specification
cable
DSX-1 Input Level
+1.5 to -7.5 dBDSX
DSX-1 Line Rate
1.544 Mbps ± 200 bps
DSX-1 Line Format
AMI, B8ZS or ZBTSI
DSX-1 Frame Format
ESF, SF or UNFR
Maximum Power Consumption
14 Watts (without doubler); 25 Watts (with doubler)
Maximum Heat Dissipation
6 Watts (without doubler); 9 Watts (with doubler)
Fusing
Internal; connected to Fuse Alarm output on pin 10
HDSL Span Voltage (Differential)
130 or 200 Vdc
Margin Indicator
Displays HDSL loop SNR margin for each HDSL
loop 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
STS, high-density slot
Dimensions
Height: 5.9 in. (15 cm)
Width: 1.4 in. (3.5 cm)
Depth: 10 in. (25.4 cm)
Weight: 1 lb. 11 oz.
9. CERTIFICATION
9.01 FCC compliance: The HLU-319, List 2D was
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 upon in a commercial
environment. This equipment generates, uses and
can radiate radio frequency energy. If it is not
installed and used in accordance with the instruction
manual, harmful interference to radio communications
may result. 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.

Section 150-319-124
Revision 03
Page 13
10. WARRANTY
10.01 PairGain Technologies warrants this product
to be free of defects and fully functional for a period of
36 months from the date of original shipment, given
proper installation. During the warranty period,
PairGain will repair or replace any unit, without cost, if
the unit is found to be defective for any reason other
than abuse, improper use or installation.
10.02 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.
10.03 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.
2120 Ritchey St.
Santa Ana, CA 92705-5101
ATTN: Repair and Return Dept.
[phone]
[phone]
11. TECHNICAL ASSISTANCE
11.01 PairGain Technical Assistance is available 24
hours a day, 7 days a week by contacting PairGain’s
Customer Service Engineering group at one of the
following numbers:
Telephone: [phone]
[phone]
Fax: [phone]
During normal business hours (8:00 AM to 5:00 PM,
Pacific Time, Monday through Friday, excluding
holidays), technical assistance calls are 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 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 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.

Section 150-319-124
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Page 14
B. APPLICATIONS WITHOUT HIGAIN
DOUBLERS (HDU-451)
12. SECTION INTRODUCTION
12.01 This section addresses HLU-319, List 2D
operation without the use of doublers. For
applications without doublers, the HLU-319 is directly
connected to the HRU-412 by the two cable pairs.
13. POWER CONSUMPTION
13.01 The three most important power demands of
an HLU-319, List 2D 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-319, List 2D, on a per-
slot and per-shelf basis, are as follows:
Maximum Power Dissipation:
• Per Slot = 7 Watts
• Per Shelf = 196 Watts
Maximum Power Consumption:
• Per Slot = 16 Watts
• Per Shelf = 448 Watts
Maximum Current Drain:
• Per Slot = 0.38 Amps
• Per Shelf = 10.5 Amps
Note:
The worst case conditions, under which these
parameters were measured, include a 9,000
ft., AWG 26 loop, 60 mA of Customer
Provided Equipment (CPE) current, a fully
loaded 28-slot shelf, and a -42.5 V shelf
battery voltage with the HLU-319 4-character
display “OFF.” For the purpose of
comparison, the HLU-319, List 1 unit
dissipates 8.5 Watts and consumes 18 Watts
per slot under similar worst case conditions.
13.02 The Maximum Power Dissipation measures
the power that is converted into heat buildup 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.
13.03 In Central Office 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 standard 28-slot 23-inch HLU-319,
List 2D shelf is 7.024 sq. ft. Thus, the maximum bay
dissipation is limited to 840 Watts. At 7 Watts per
slot, this limits the number of occupied slots to 120
per bay.
13.04 The thermal loading limitations, imposed
when using the HLU-319, List 2D in a Controlled
Environmental Vault (CEV) or other enclosures, are
determined by applying the HLU-319, List 2D's power
parameters to the manufacturer's requirements for
each specific housing.
13.05 The Maximum Power Consumption is the total
power that the HLU-319, List 2D consumes or draws
from its -48 V shelf power source. This parameter is
needed when the HLU-319 is remotely located to its
serving CO. It determines the battery capacity
required to maintain an 8-hour standby battery
reserve for emergency situations; thus limiting the
maximum number of plugs per line unit’s remote
enclosure. Use the above data to perform this
analysis on a case-by-case basis.
13.06 The Maximum Current Drain is the maximum
current drawn from the shelf power supply when it is
at its minimum voltage (-42.5 V). It determines the
shelf fusing requirements. All HLU-319 shelves are
partitioned into two equal halves, each fused at 10
amps for a total of 20 amps per shelf. A fully loaded
shelf draws 10.5 amps worst case. This is within the
20 amp fuse limit.
13.07 Heat baffles should be placed between every
other shelf, in racks containing more than two shelves.
This technique deflects the rack’s heat outward and
reduces thermal stress on the plugs.
14. LOOPBACK OPERATION
14.01 The HiGain system 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 5) Smart-Jack in-band loopback
codes, and thus emulates the functions of a standard
Network Interface Device (NID). This option can be
ENAbled or DISabled from either the front panel
buttons or the terminal System Settings Menu.

Section 150-319-124
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Page 15
14.02 In addition to the Smart-Jack loopback, the
HiGain system can be configured for one of five
special in-band loopback (SPLB) command
sequences. These are selected from the SPLB user
options, which are shown in Table 1 and Figure 11
(non-doubler applications). The non-doubler loopback
locations are shown in Figure 6.
14.03 “GNLB” is the HiGain system Generic
Loopback code. The GNLB allows in-band codes to
loop up either the HLU/NLOC (4 in 7) or the
HRU/NREM (3 in 7) toward the network. In addition, it
allows in-band codes to loop up the HLU/CREM (6 in
7) or the HRU/CLOC (5 in 7) toward the customer.
Either loop-up condition is terminated (looped down)
with the (3 in 5) loop-down code. Both in-band codes
must be present for 5 seconds before the HiGain
system responds. Table 2 lists the test procedures
that apply when using the GNLB mode.
14.04 The A1LB loopback selection complies with
that proposed for HDSL systems in the T1E1.4/92
recommendation with the following additions (see
Table 3):
• Query loopback
• Intelligent Office Repeater (IOR) power-
down
• Three loopback time-out choices
• Initiation from either end
• Repeating bit error signatures
• Alternate query loopback
These additions make A1LB identical to A2LB, but
they retain separate identities to allow future T1/E1
enhancements to A1LB without affecting A2LB.
14.05 A2LB through A5LB are four special
addressable repeater loopback functions, which are
supported by the List 2D version of the HiGain
system. These loopbacks provide the HiGain system
with sophisticated maintenance and troubleshooting
tools. Table 4 through Table 7 list the details of these
SPLB functions. A2LB and A5LB are patterned after
the Teltrend addressable T1 repeater loopbacks.
A3LB and 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 system
customers:
• A2LB (Teltrend) = Southwestern Bell
• A3LB (Wescom) = New England Telephone
• A4LB (Wescom Mod 1) = New York
Telephone
• A5LB (Teltrend Mod 1) = Southern New
England Telephone (SNET)
14.06 A5LB differs from A2LB in that A5LB does not
block the arming (3 in 5) code from exiting the HLU-
319, List 2D into the network. A2LB can be
configured to either block this arming code after two
seconds and replace it with the AIS code or unblock it
by executing the Far-End Activate code. Since A5LB
never blocks the arming code from exiting the HLU-
319, List 2D, 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.
Refer to the PairGain HiGain-2 Intelligent Repeater
Application Note #910 Part #325-910-100 for more
SPLB details.
14.07 When T1 loopback tests are performed on the
HiGain system with metallic loopback connections at
either end, the T1 code, which exists at the metallic
loopback interface, may be different from the T1 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-319, List 2D and
HRU-412 set their own codes independently 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-412 has a metallic loopback, and
the HLU-319, List 2D receive pattern code is changed
from AMI to B8ZS, and next, the all “0” pattern is sent
into the HLU-319, List 2D, then the HLU-319, List 2D
changes to its B8ZS mode while the HRU-412
remains in its AMI mode, and thus loops all “0.” This
causes the HRU-412 to indicate an LOS condition,
which causes the HLU-319, List 2D to output the AIS
pattern.
14.08 The HiGain system may take longer than
normal to respond to in-band loopback commands
when its framing mode is set to UNFR and the in-band
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
the HiGain system to reject some sequences. This
can extend the detection interval.

Section 150-319-124
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Page 16
14.09 Pressing both the Mode and SEL front panel
push buttons, for at least three seconds, initiates a
Manual Loopback session. This session allows the
user to select one of four HiGain system loopbacks.
The message, “MAN LPBK,” appears on the front
panel display followed by the message “NLO?” If the
SEL button is pressed at this time, an NLOC loopback
is executed changing the message from “NLO?” to
“NLOC.” If the Mode button is pressed 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 in the sequence listed.
This interactive button procedure permits any of the
four HiGain loopbacks to be executed. The next
loopback option can be presented by pressing the
Mode push button, however, the previously executed
loopback will remain active until the SEL push button
is pressed, and a different loopback is activated. If,
after 30 seconds, neither button is pressed, this
manual loopback session terminates, and the normal
margin displays reappear. If this time-out occurs with
an active loopback in effect, the appropriate loopback
and loop margin messages appear. Once the manual
loopback session terminates, the loopback remains in
effect until it times out in accordance with the user
LBTO setting. It can also be terminated by re-
entering the manual loopback mode and selecting
another loopback. Only one loopback can exist at any
given time. Pressing both the Mode and SEL buttons
again for three seconds, terminates any active
loopback, ends the Manual Loopback session, and
returns the display to normal. Note that these same
loopbacks can be initiated from the RS-232
maintenance port by choosing the Loopback Mode,
option D, from the Main Menu. This displays the
Loopback Menu (see Figure 11), from which any of
the loopbacks can be initiated/ terminated.
15. TESTING
15.01 Table 2 through Table 7 provide step-by-step
test procedures for the HLU-319, List 2D as a function
of the loopback option selected. These procedures
allow verification of the integrity of the HDSL channels
at every module location as well as the DS1 channels
to the customer and the local DSX-1 interface.
15.02 The HLU-319, List 2D 4-character front panel
display has many useful system diagnostic messages.
They are listed in Table 10. This display turns on
when power is initially applied to the HLU-319, List
2D. To conserve power, the display remains on for
only five minutes when neither the Mode or SEL
buttons are pressed. The use of either button
activates the 4-character display and restarts the
5-minute power control timer.
15.03 If trouble is encountered on the HLU-319 List
2D DSX-1 interface, verify that the HLU-319, List 2D
is making a positive connection with its mounting
assembly (shelf) connector. Also, verify that the HLU-
319, List 2D equalizer is set to the correct distance
range per Table 1. All installations should be set to
the largest distance range value that does not exceed
the distance from the DSX-1 to the shelf.
15.04 The transmit and receive DSX-1 ports have
splitting, access and bridging, miniature 210-series
jacks, as shown in Figure 2. Connecting one cable
between the two Bridging jacks, and another between
the two Line jacks, splits the XMT and RCV and
creates metallic loopbacks toward both the DSX-1 and
the HLU-319, List 2D. If plugs are inserted into both
Line jacks, the BRG jacks can be used to send and
receive test patterns toward the DSX-1.

Section 150-319-124
Revision 03
Page 17
Figure 6. HLU-319, List 2D Non-Doubler 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 150-319-124
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Page 18
TABLE 2. HLU-319 GNLB TEST PROCEDURES
Step Action
1 Have the CO tester send the HRU-412 (3 in 7) in-band loop-up code for five seconds. Observe that
the HLU-319, List 2D displays the “NREM” message indicating an HRU loopback is in effect (see
Figure 6).
2 Have the CO tester transmit a DSX-1 test signal into the HLU-319, List 2D 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-319, List 2D display returns to normal.
4 Have the CO tester send the HLU-319, List 2D (4 in 7) in-band loop-up code for five seconds.
Observe that the HLU-319, List 2D displays the “NLOC” message, which indicates that an HLU-
319, List 2D loopback is in effect.
5 Repeat Step 2. If the test passes, the problem is in the cable pair or the HRU-412. 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-319, List 2D
with the Mode and SEL push buttons (see Section B Paragraph 14.09).
7 The HLU-319, List 2D can be looped up from the remote location (CREM) by issuing the (6 in 7)
command at the HRU-412 DS1 input port.
8 The HRU-412 can be looped up from the remote location (CLOC) by issuing the (5 in 7) command
at the HRU-412 DS1 input port.

Section 150-319-124
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Page 19
TABLE 3. HLU-319 A1LB TEST PROCEDURES
Step Action
1 Send the in-band Arming and NI LPBK code 11000 into the HLU-319, List 2D, for at least
five seconds or at least four repetitions of the 16-bit ESF data link Arming code 1111 1111
0100 1000 (FF48). (Left bit arrives first.)
2 Monitor the output of the HLU-319, List 2D for the return of the pattern. Return of pattern
indicates that either the HRU-412 has looped up (if the Smart-Jack Loopback option is
ENAbled) or an external NI has looped up (if the Smart-Jack Loopback option is DISabled),
and that the HLU-319, List 2D and HRU-412 units have been Armed. Verify that the HLU-
319, List 2D display intermittently indicates “Arm” and also “SMJK,” if the HRU-412 is in
loopback. Also verify, if possible, that the Loopback LED of the HRU-412 is flashing
(indicating that the HRU-412 is armed), or, that the Loopback LED lights steadily (indicating
that the HRU-412 is both armed and in loopback).
3 Once armed the HLU-319, List 2D can be looped back (NLOC in Figure 6) by sending the
Intelligent Office Repeater Loopback (IOR LPBK) activation code 1101 0011 1101 0011
(D3D3) for at least five seconds. The tester observes the following activation response:
• Two seconds of AIS (all ones), followed by:
• Five seconds of returning data pattern, followed by:
• 231 logic errors (including the frame bit) occur in the returned pattern (20 errors if
ILR-2 was sent), followed by:
• Normal looped data.
Note:
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 the Time-out
Override and Query commands. It also applies (with the appropriate number of bit
errors) to the other ILR commands.
The HiGain Line Unit is now in Logic Loopback (NLOC of Figure 6). The display on the HLU-
319, List 2D periodically shows “NLOC” (network local loop) and “Arm” (the HLU-319, List 2D
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 (D5D6) is received, the “activation
sequence,” described in “3” 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-
319, List 2D down is to issue the Intelligent Repeater Loop-down (IR LPDN) code 1001 0011
1001 0011 (9393) or to issue the NI LPDN and Disarm code 11100. The automatic time-out
timer is restored during subsequent loopback sessions.
4 Upon completion, the tester sends the IOR LPDN code 1001 0011 1001 0011 (9393) to loop
down the HLU-319, List 2D. The unit remains armed, however, as indicated by the “Arm”
message on the HLU-319, List 2D and the flashing of the HRU-412 Loopback LED.
Table continued on next page

Section 150-319-124
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Page 20
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) (see Figure 6). A customer tester can activate loopbacks CLOC or CREM.
ADDRESSABLE 1 (A1LB) REPEATER LOOPBACK COMMANDS
ARMING or NI LPBK (in-band) Arming code 11000 11000 ...
ARMING or NI LPBK (ESF data link) Arming code 1111 1111 0100 1000 (FF48)
IR LPDN or DISARM (in-band) Disarming code 11100 11100 ...
DISARM (ESF data link) Disarming code 1111 1111 0010 0100 (FF24)
IOR LPBK
(NLOC and CREM 231 errors) HLU Loop-up 1101 0011 1101 0011 (D3D3)
ILR-2 LPBK
(NREM and CLOC 20-bit errors) HRU Loop-up 1100 0111 0100 0010 (C742)
IR LPDN Loop-down
(HLU or HRU) 1001 0011 1001 0011 (9393)
IR QUERY LPBK Query
Loopback 1101 0101 1101 0101 (D5D5)
IR ALTERNATE QUERY LPBK Alternate Query
Loopback 1101 0101 1110 1010 (D5EA)
TIME-OUT OVERRIDE Loopback Time-
out Override 1101 0101 1101 0110 (D5D6)
FAR END NI ACTIVATE Unblock AIS
and pass 2 in 5 1100 0101 0101 0100 (C554)
IOR POWER-DOWN (HLU) Removes HDSL
line power 0110 0111 0110 0111 (6767)
Note:
The left-most bit arrives first in all sequences. The detection algorithm functions
reliably with a random 10-3 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, the HiGain system returns to its normal unlooped and unarmed state.
6 After testing is complete, send the universal Intelligent Repeater Loop-down (IR LPDN) code if
the system is to loop down 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 All of the above loopbacks can also be initiated from the front panel of the HLU-319, List 2D
with the Mode and SEL push buttons (see Section B Paragraph 14.09).