PairGain HiGain-2 HRU-612 User manual

PAIRGAIN TECHNOLOGIES SECTION 150-612-102
Technical Practice Revision 03
Engineering - PLANT Series January 30, 1996
Page 1
PAIRGAIN TECHNOLOGIES HIGAIN-2™REMOTE UNIT
MODEL HRU-612
List 2 PairGain #150-1218-02 CLEI Code: T1L1HJJ3AA
CONTENTS PAGE
A. PRODUCT OVERVIEW
1. GENERAL 2
2. APPLICATIONS 2
3. SPECIFICATIONS 3
4. CERTIFICATION 3
5. WARRANTY 4
6. TECHNICAL ASSISTANCE 4
B. FUNCTIONAL DESCRIPTION
7. FUNCTIONAL OPERATION 4
8. FRONT PANEL 6
9. OPTIONS 7
10. LOOPBACKS 9
C. INSTALLATION AND TEST
11. INSTALLATION 10
12. TESTING 12
CAUTION
This product incorporates static sensitive
components. Proper electrostatic discharge
procedures must be followed.
Figure 1. HRU-612 List 2 Front Panel. The PairGain
HRU-612 is the remote side of a single pair repeaterless
T1 transmission system.

Section 150-612-102
Revision 03
Page 2
A. PRODUCT OVERVIEW
1. DESCRIPTION AND FEATURES
1.01 PairGain’s HiGain-2 Remote Unit Model
HRU-612, List 2, Figure 1, is the remote end
of a single pair repeaterless T1 transmission system.
It differs from the HRU-612, List 1 in the
implementation of the SAIS, DIS(abled) option and in
its ability to be locally powered. When used in
conjunction with a HiGain-2 Line Unit HLU-611 the
system provides 1.544 Mb/s transmission on one
unconditioned copper pair over the cable ranges
shown in Table 1. The HiGain-2 system utilizes
2B1Q VHDSL (Very High-bit-rate Digital Subscriber
Line) transmission technology. HiGain-2 complies
with the ANSI T1E1.4, T1.403-1989 and T1E1.4/92-
002R2 technical standards & recommendations. The
HRU-612 List 2 mounts in a single slot of any industry
standard 400 mechanics shelf or in equivalent
enclosures manufactured by PairGain Technologies.
The system also 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 03 — January 30, 1996
a) Removed the local power and sealing
current options.
1.03 Features of the HRU-612 Issue 1 List 2
HiGain-2 Remote Unit are as follows:
• ANSI T1.403 DS1 Customer Interface
• VHDSL Line Powered operation - no local
power required
• Front Panel DS1 and VHDSL Status
Display
• Generic & addressable repeater Loopback
activation codes.
• Metallic smart-jack loopback. Conforms to
TR-TSY-000312.
• Provisioning switches for CPE current,
RCV LBO and XMT LOS initiated loopback
or AIS.
• Front panel jacks for test access
• RS-232 front panel terminal access for
craft
• CPE current monitor test points
• Front panel VHDSL margin threshold
indicator.
• Lightning and power cross protection on
VHDSL and DS1 interfaces
• 1568 kbps/s full-duplex 2B1Q VHDSL
Transmission on 1 pair
• DS0 blocking.
2. APPLICATIONS
2.01 The primary application of the HiGain-2
System is to provide a quick and cost-
effective way of delivering T1 High Capacity Digital
Service (HCDS) to customers over a metallic cable
pair. The HiGain-2 system can be deployed on 1
unconditioned, non-loaded pair of wires without
repeaters, and without the need for either bridged tap
removal.
2.02 The general guidelines, on which the range
deployment rules in Table 1 are based,
require that the VHDSL HiGain-2 loop, which
operates at twice the line rate of standard HiGain
HDSL products, have less than 35 dB of loss at the
2B1Q line rate of 392 kHz, @ 135 ohm source and
load impedances.
2.03 The HiGain-2 system operates with any
number of other T1, POTS, Digital Data
Service (DDS) or other HiGain-2 Systems sharing the
same cable binder group. HiGain-2 systems can be
used with customers requiring DS1 service on a
temporary or permanent basis. HiGain-2 also
provides a means of quickly deploying service in
advance of fiber-optic transmission systems. Using
HiGain-2 T1 service can be connected within a few
days or even a few hours. Fiber optic systems can
be installed at a leisurely pace and cut-over from
HiGain-2 when the time allows. The HiGain-2 system
can then be easily removed and utilized elsewhere.

Section 150-612-102
Revision 03
Page 3
TABLE 1. HIGAIN-2 VHDSL LOOP LIMITS
Cable Gauge Loss @ 392
kHz dB/kft Ohms per kft Maximum Loop For 35 dB Loss Ohms @ Maximum Loop Length
26/0.4 mm 4.97 83.3 7.0 kft / 2.13 km 583
24/051 mm 3.87 51.9 9 kft / 2.74 km 467
22/0.61 mm 3.01 32.4 12 kft / 3.66 km 389
19/0.91 mm 2.17 16.1 16 kft / 4.87 km 258
3. SPECIFICATIONS
VHDSL Line Code
1568 kbps/s 2B1Q full duplex
VHDSL Output
+13 dBm +/- 0.5 dB @ 135 ohms
VHDSL Line Impedance
135 ohms
VHDSL Line DC resistive signature
180 Kohms
Maximum Provisioning Loss
35 dB @ 392 kHz, 135 ohms
Line Clock Rate
Internal Stratum 4 clock
VHDSL Startup Time
15 seconds typ., 60 seconds max.
One-way DS1 Delay
<220 microseconds
DS1 Line Impedance
100 ohms
DS1 Pulse Output
0 dB (RLEV = 0), -15 dB (RLEV =15).
DS1 Input Level
> -22.5 dB
DS1 Line Rate
1.544 Mb/s +/- 200 bits/sec
DS1 Output Wander (MTIE & TVAR)
Less then 1.5 UI (Unit Interval) in 15 minutes
DS1 Line Format
AMI, B8ZS or ZBTSI
DS1 Frame Format
ESF, SF or unframed
Power Consumption
6 watts typ. 8 watts max.
Electrical Protection
Secondary surge and power cross protection on
all DS1 & VHDSL ports.
Operating Temperature and Humidity
0 to +50º Celsius, 5 to 95% (non-condensing)
Mounting
Single width 400-type mechanics slot.
Dimensions
5.6” H x 1.4”:W x 5.6” D.
4. CERTIFICATION
4.01 FCC Compliance: The HRU-612 List 2 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.
4.02 UL Recognized: The HRU-612 List 2 is a UL
Recognized component. Use normal
caution when installing or modifying telephone lines.
Dangerous voltages may be present. It is also
considered imprudent to install telephone wiring
during a lightning storm. Always disconnect all
telephone lines and power connections from wall
outlets before servicing or disassembling this
equipment.
4.03 CSA Certification: The HRU-612 List 2 has
been tested and found to comply with CSA
Standard C22.2-950 with telecommunication
features.

Section 150-612-102
Revision 03
Page 4
4.04 Refer to the installation section of the
appropriate instruction manual for the unit
you are installing for:
• Cabling information
• Proper connections
• Grounding information
• Line vs local power
All wiring external to the product(s) should follow the
provisions of the current edition of the National
Electrical Code.
5. WARRANTY
5.01 PairGain Technologies warrants this product
to be free of defects and to be fully
functional for a period of 36 months from the date of
original shipment, given proper installation and
regular maintenance. PairGain will repair or replace
any unit without cost during this period if the unit is
found to be defective for any reason other abuse or
improper use or installation.
5.02 This module should not be field repaired. If
it fails, replace it with another unit and return
the faulty unit to PairGain for repair. Any
modifications of the unit by anyone other than an
authorized PairGain representative will void the
warranty.
5.03 If a unit needs repair, call PairGain for a
Return Material Authorization (RMA)
number and return the defective unit, freight prepaid,
along with a brief description of the problem, to:
PairGain Technologies, Inc.
14402 Franklin Avenue
Tustin, CA 92680
ATTN: Repair and Return Dept.
[phone]
[phone]
5.04 PairGain will continue to repair or replace
faulty modules beyond the warranty
program at a nominal charge. Contact your
PairGain sales representative for details and pricing.
6. TECHNICAL ASSISTANCE
6.01 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 - 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 for posting
requests or questions. This system is available 24-
hours-a-day by calling [phone].
Transmission speeds up to 28.8 kbps are supported
with a character format of 8-N-1.
B. FUNCTIONAL DESCRIPTION
7. FUNCTIONAL OPERATION
7.01 HiGain-2 utilizes PairGain’s 2B1Q VHDSL
transceiver technology to establish a full-
duplex 1568 Kbps data channels between the HLU
and a remotely mounted HRU-612 HiGain-2 Remote
Unit.
7.02 The HRU-612 power supply converts the
metallic 170 Vdc power feed that is received
on the VHDSL pair to voltages and currents required
by the HRU-612 circuitry. The power supply
generates +5, -5 and 30 Vdc outputs. The 30V
output is converted to a 60 mA current feed used to
simplex power the NID (Network Interface Device).
Caution should be used when the HRU is used to
power CSUs. Some CSUs require more output
voltage than the 30 volts provided by the HRU. The
HRU can not power both an NID and a CSU at the
same time.

Section 150-612-102
Revision 03
Page 5
7.03 The HRU-612 typically dissipates 6 watts of
power and may consume up to 8 watts
when feeding 60 mA. of simplex current to the CI.
7.04 The worst case -48V power consumption by
a HiGain-2 system from the CO is 18 watts
per DS1 service.
7.05 A 9-pin (RS-232) DB-9 connector,
configured as DCE (see Figure 3), is
provided on the front panel of the HRU-612. This
provides access to the monitoring features of
HiGain-2’s maintenance, provisioning and
performance monitoring interface. A very basic
interface is available via a ‘dumb terminal’. Figures
7 through 13 show the menu selections that are
available from the terminal. Table 3 defines the
various terms used in the screen displays. 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 baud. Note
that if the RS-232 port in an HRE-421 is used to
access the HRU-612, a null modem must be used
since the HRE-421 is configured as DTE .
7.06 The HRU-612 provides embedded status
monitoring functions that are accessed via
the RS-232 port. A main menu, shown in Figure 7,
is presented when a terminal is connected as
described in the previous paragraph. Figures 7-13
illustrate the displays provided from the terminal
port. Information displayed shows the status of the
HLU at the distant end of the VHDSL spans as well
as the HRU-612. The HLU shares its status with the
HRU-612 via the embedded operations channel so
there is no need to physically connect to the distant
end for its status.
Figure 2. HRU-612 List 2 Block Diagram.

Section 150-612-102
Revision 03
Page 6
8. FRONT PANEL
8.01 DS1.
The top 60% of the front panel
addresses the following DS1 interface
features:
60 mA MON - These two test points
allow the 60 mA CPE current option, if
selected, to be measured. The current
flowing is related to the voltage
measured across the “ + “ and “ - “ test
points by the following relationship:
CPE CURRENT =1 MA / 1 MV
Typical readings range from 55 to 65 mv
which equate to a 55 to 65 mA current
range.
RCV & XMT ACCESS JACKS - These
provide both splitting and monitor
access jacks to the CPE DS1 interface.
See Figure 2 for circuit details. Note
that these jacks are transformer isolated
from the CPE DS1 metallic interface.
• ALM
REM LOS - RED LED that indicates a
Loss Of Signal at the T1 input to the
REMote (HLU) unit. This condition
causes the HRU to transmit the AIS
pattern to towards the CPE.
LOC LOS RED LED - that indicates a
Loss Of Signal at the T1 input to the
LOCal (HRU) unit. This condition
causes HiGain-2 to either transmit the
AIS pattern towards the DSX-1 or to
execute a logic loopback in the HRU as
a function of the TLOS user option
setting. See Paragraph 9.01 for details.
• LB
NET - GREEN LED indicating the HRU
is in a loopback state in which the signal
from the NETwork is being looped back
to the NETwork.
CI - YELLOW LED indicating the HRU is
in a loopback state in which the signal
from the customer interface (CI) is being
looped back to the CI.
BUTTON - Depressing this front panel
button for 5 seconds forces the HRU
into its NREM metallic loopback state.
The unit can be unlooped by either
depressing the button again for 5
seconds or via the standard loopdown
coded messages
• CODE
B8ZS - GREEN LED indicating that the
user DS1 code option is set to B8ZS. If
however the user DS1 code option is set
to AUTO, this LED indicates that the
code of the DS1 signal being received
at the HRU’s DS1 input is B8ZS.
AMI - YELLOW LED indicating that the
user DS1 code option is set to AMI. If
however the user DS1 code option is set
to AUTO, this LED indicates that the
code of the DS1 signal being received
at the HRU’s DS1 input is AMI.
BPV - RED LED that flashes every time
a Bipolar Violation, other than those
associated with a B8ZS code, is
received at the HRU’s DS1 input.
• FRM
ESF - GREEN LED indicating that
framing pattern of the signal being
received at the HRU’s DS1 input is
ESF.
HLU-612
DCE
FEMALE MALE
2
5
3
2
5
3
RD(RECEIVE DATA)
TD(TRANSMITDATA)
GND
DB9
DB9
DTE
DTE
TERMINAL
TERMINAL
3
2
7
DB25
Figure 3. DB-9 Pin-outs.

Section 150-612-102
Revision 03
Page 7
SF
YELLOW LED indicating that framing pattern of
the signal being received at the HRU’s DS1
input is SF.
ERR
RED LED indicating a DS1 frame error has
occurred.
Note the FRM LED remains off if the HRU input
pattern is unframed or if the HiGain-2 FRMG
option is set to its unframed (UNFR) mode.
8.02 VHDSL.
The lower 40% of the front
panel addresses the following VHDSL
interface features.
OK
GREEN LED that flashes while the VHDSL Loop
is synchronizing with the HLU. A solid green
state indicates that Loop is properly
synchronized with the HLU.
MAR
YELLOW LED indicating that the HRU’s S/N
MARgin on the VHDSL Loop has dropped
below the user defined margin threshold value.
This option is set at the HLU in the System
Settings menu of the maintenance interface
system at the RS-232 maintenance port.
ES
RED LED that flashes ever second in which at
least one VHDSL CRC error is detected.
9. OPTIONS
9.01 The HiGain-2 List 2 system has several
special loopback (SPLB) options that
are set at the HLU. Refer to practice # 150-611-
100 for more details. The HRU also has three
user options set by switches located at the back
of the unit as shown in Figure 4. Each switch
has two settings as follows (refer to the block
diagram in Figure 2 for details):
• I-CPE
0 *: Sets the CPE current to 0 mA..
60: Sets the CPE current to 60 mA to power an
external NID.
• TLOS-LB
DIS* : A loss of the T1 XMT signal from the CPE
causes the HLU to transmit the AIS signal
towards the DSX-1 and does not cause the HRU
to enter its logic loopback state.
EN: A loss of the T1 XMT signal from the CPE
forces the HRU to enter its logic loopback state
(TLOS in Figure 5). While in this loopback
state, the HRU transmits the AIS signal towards
the CPE and returns the Network signal back to
the Network. The HLU displays the message
TLOS in its 4 character front panel read-out.
This condition remains until a valid T1 signal is
received from the CPE or until a loopdown
command is issued. Note that once the TLOS
initiated loopback has occurred, it can not
reoccur until the CPE T1 signal has been
reapplied and then removed. This “latching”
feature prevents the HRU from oscillating into
and out of TLOS loopback when a loopdown
command is issued in the absence of a T1
signal from the CPE.
Figure 4. HRU-612 Manual Switches

Section 150-612-102
Revision 03
Page 8
RLEV
0 *: Configures the T1 RCV LEVEL to 0 dB.
This sets the T1 output signal level from the
HRU towards the NI to 0 dB. This setting is
recommended when the HRU does not function
as the NID but is connected to an external NID.
It allows the external NID to set the appropriate
NI level.
15 : Configures the T1 RCV LEVEL to -15 dB.
This sets the T1 output signal level from the
HRU towards the NI level to -15 dB. This
setting is recommended when the HRU
functions as the NID.
Note that the “ * ” denotes the factory setting.
Figure 5. HRU-612 Loopbacks.

Section 150-612-102
Revision 03
Page 9
10. LOOPBACKS
10.01 Figure 5 shows all four HRU loopbacks. Of
these four, the TLOS and CLOC are logic
loopbacks. They occur in the digital multiplexer
section of the HRU as shown in Figure 2.
10.02 Both the SMART-JACK and NREM
loopbacks shown in Figure 5 execute the
standard NID metallic loopback. Their only
difference is their initiating sequence. NREM is
initiated by the HRU front panel pushbuttons, the
maintenance terminal, the HLU front panel
pushbuttons, or the 3 in 7 band command. The
SMART-JACK loopback is only initiated by the
standard 3 in 5 inband loop-up command. It has two
modes of operation as determined by the two states
(ENA or DIS) of the AIS on SMJK/NREM option that
is controlled by the HLU. The ENA option causes
the HRU to transmit the AIS signal towards the NI.
The DIS option turns off this AIS/NI signal
10.03 ENA: Upon detection of a valid SMART-
JACK loopback command, a metallic
loopback relay (see Figure 2 for its location) is
energized and the T1 interface chip transmits the
AIS pattern to the NI and also back to the HRU’s T1
receiver circuit. In addition, the customer’s T1 XMT
input is disconnected and terminated into 100 ohms.
The AIS pattern is examined by the HRU for its
overall integrity. This pre-looped tests lasts for
about 100 milliseconds and terminates in one of the
following two conditions:
A. PRE-LOOP FAILED: If the transmit & receive all
1’s patterns do not match, a problem in the HRU is
indicated and HiGain-2 declares an HRU PRE-
LOOPBACK FAIL condition. This terminates the
loopback test and returns the HRU to its unlooped
normal state. Note that the circuit impairments
could also prevent the loopback from occurring.
B. PRE-LOOP PASSED: If the transmit and receive
patterns do match, a HRU PRE LOOPBACK PASS
condition is declared. All active circuits are working.
The metallic loopback relay remains closed and, in
addition, a logic loopback within the HRU is enabled.
This logic loopback is required in order to present
the all 1’s pattern to the NI and at the same time to
loop the signal, being received from the network,
back towards the network. HiGain-2 is now in its
AIS/ENA “smart-jack” loopback state. It remains in
this state until a loopdown command is detected or
the default time out period (if enabled) expires.
10.04 When the HRU is in its AIS/ENA smart-jack
metallic loop back state, its T1 input LOS,
Code & Frame monitoring circuits are connected to
the unframed AIS pattern which is being looped
back to these circuits through the loopback relay.
The CPE input signal is no longer being monitored
since its input circuit has been opened and
terminated into 100 ohms. This forces the FRM
LED off, the LOC LOS LED off and the CODE LED
to indicate AMI if the HLU CODE option is set to
either AUTO or AMI. It will indicate B8ZS if the
CODE option is set to B8ZS.
10.05 As can be seen, this AIS/ENA metallic
loopback scenario includes and therefore
tests all HiGain-2 active circuits and fully conforms
with TR-TSY-000312. In this sense it out performs
the loopback function found in most standard NID
devices since these devices do not include either the
AIS generator or the CI T1 LOS detector in their
loopback path.
10.06 DIS: This metallic loopback state is initiated
in the same manner as it is when the ENA
option is chosen. However, once initiated, the AIS
signal is not sent to the NI. Instead the HRU’s T1
RCV port is disconnected from the RCV signal and
terminated into a 100 ohm termination. This causes
an LOS condition towards the NI which alerts the
customer to the off-line condition of the circuit. In
addition, the HRU’s T1 XMT port is opened and
terminated into 100 ohms. No logic loopback is
required since the relay is performing the network
signal loopback function. This simple metallic
loopback state remains until a loopdown command
is issued or the default timer (if enabled) expires.
10.07 When the HRU is in its AIS/DIS smart-jack
metallic loop back state, its T1 input LOS,
Code & Frame monitoring circuits are connected to
the network’s signal which is being looped back to
these circuits through the loopback relay. The CPE
input signal is no longer being monitored since its
input circuit has been opened and terminated into
100 ohms. The FRM & LOC LOS LEDs indicate the
framing pattern of the network test signal. The LOC
LOS LED will always be off. The CODE LED
indicates AMI or B8ZS if the CODE option is set to
either AMI or B8ZS respectively. Its state is
determined by the test pattern if the CODE option is
set to AUTO.

Section 150-612-102
Revision 03
Page 10
10.08 The TLOS initiated loopback is a logic
loopback that is equivalent to the PRE-
LOOP PASSED AIS/ENA loopback option. The
metallic loopback relay can not be closed because
the XMT port must be kept open so it can detect the
presence of the customer’s signal and terminate the
loopback state.
10.09 The HRU can be looped up (CREM) from
the HRU DS1 interface with a 6 in 7 in-band
command. The HRU itself can be looped up
(CLOC) from the HRU DS1 interface with the 5 in 7
in-band command. Both command patterns must
last for at least 5 seconds and can be framed or
unframed. The loop down command for both is the
standard 3 in 5 (five second) pattern.
C. INSTALLATION AND TEST
11. INSTALLATION
11.01 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.
11.02 The HRU-612, List 2 is designed to mount in
PairGain’s HRE-421 (double width, single
mount), HRE-422 (double width, double mount),
HRE-427 (double width, 7 unit wall mount), or HRE-
420 (single width, single mount). For outdoor
applications, the HRE-423 (3 unit) and HRE-450
(single width, single mount) enclosures are
available. The HRU is also compatible with industry
standard 400 type multi-mount shelves. The HRU’s
pin-outs are shown in Figure 6.
Figure 6. HRU-612 Pin-outs.

Section 150-612-102
Revision 03
Page 11
TABLE 2. HRU-612 Test Procedures.
Step Action
1 Depress the loopback LB button on the HRU front panel for at least 5 seconds.
2 Verify that the GREEN HRU front panel loopback LB NET LED turns on, indicating that the HRU is in
its (NREM) loopback state. Also verify, if possible, that the HLU displays the message ”NREM” also
indicating that the HRU is in loopback (see Figure 5).
3 Have the C.O. tester transmit a T1 test signal into the HLU and measure that the returned (looped)
signal is error free.
4 If the above test fails, remove the HRU from its loopback state by again depressing the HRU loopback
button for 5 seconds. Verify that the loopback NET LED is off.
5 Have the C.O. tester send the HLU (4 in 7) in-band loop-up (NLOC) for 5 seconds. Verify that the HLU
displays the message “ NLOC” indicating that the HLU unit is in its network loopback state.
6 Repeat step 3. If the test passes, the problem is in the cable pair or the HRU. If it fails, the problem is
in the C.O.
7 To verify that the proper ports are use for the VHDSL & DS1 pairs, use an ohm-meter to verify that the
VHDSL HRU-612 port has a 180 k T to R resistive signature in contrast to the DS1 ports which have a
15 ohm T to R resistive signature.
8 If the CPE 60 mA. switch option is set. Verify that the external NID is under power and that the voltage
across its front panel “60 mA MON” test points measures between 55 and 65 mv. This indicates that the
CPE current is between 55 & 65 mA. Note that the external NID’s LOOP POWER option must be set to
its “THRU” position when powered by the HRU.
NOTE: When T1 loopback tests are made on the HiGain-2 system with external 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 option is set to AUTO. 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 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.

Section 150-612-102
Revision 03
Page 12
12. TESTING
12.01 Table 2 provides a step by step test
procedure for the HRU-612 unit. This
procedure allows verification of the integrity of the
VHDSL channel to the HLU Line Hit as well as the
DS1 channels to the customer and the HLU DSX-1
interface. Table 3 lists the HLU status messages
which may also be helpful when coordinating turn-up
with CO personnel.
12.02 The HLU’s 4 character front panel has many
useful diagnostic messages. They are listed
in Table 3.
12.03 If trouble is encountered at the T1 interface,
verify that the unit is making a positive
connection with the mounting assembly’s connector.
TABLE 3. HLU 4 CHARACTER FRONT PANEL MESSAGES.
Message Full Name Description
CREM Customer Remote Loopback Signal from customer is looped back to customer at HLU-
611
NLOC Network Local Loopback DSX signal is looped back to DSX at HLU
CLOC Customer Local Loopback Signal from Customer is looped back to customer at HRU-
612
NREM Network Remote Loopback DSX signal is looped back to DSX at HRU
SMJK Remote Smartjack Loopback Signal from DSX is looped back at HRU by the HRU
smartjack module.
TLOS Transmit Loss of Signal The HRU is in a logic loopback state caused by a loss of its
T1 input from the NI, if enabled by the SAIS option.
FERR Framing Bit Error Occurred Framing bit error occurred at HLU T1 input
LBPV Local Bipolar Violation A bipolar violation has been received at the T1 input to the
HLU-611.
SIG1 Signal The HLU & HRU transceivers are trying to establish
contact with each other.
ACQ1 Acquisition The HLU & HRU multiplexers are trying to establish
synchronization over each loop.
HES HDSL CRC Error At least 1 CRC error on the VHDSL Loop in the last second.
ARM HiGain-2 System ARMED Armed to respond to Intelligent Repeater Loop Codes
ACO Alarm CutOff A MNRALM has occurred, and been retired to an ACO
condition, by depressing the SEL button on the HLU front
panel.
SELF TEST Self Test The HLU is in a self test mode. This occurs every power
ON/OFF cycle.
ALRM Alarm Condition Exists A minor alarm condition is in effect.
Table continued on next page

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TABLE 3. HLU 4 CHARACTER FRONT PANEL MESSAGES (CONTINUED)
Message Full Name Description
M =xx VHDSL Loop Margin Indicates the power of the received VHDSL signal relative
to noise. Any value of ‘06’ or greater is adequate for
reliable system operation.
PWR FEED
SHRT Power Feed Short Indicates a short between the VHDSL pair.
PWR FEED
OPEN Power Feed Open Indicates an open circuit in the T&R of the VHDSL pair.
BAD RT? No response from HRU The HDSL Power feed circuits are good, but the HLU does
not receive any response from the HRU. Thus the HRU’s
integrity is questionable.
VER HLU Software Version # This is displayed during the System Settings review mode.
Depress the Mode button for 3 seconds.
LIST 0xL HLU’s List # Displayed during System Settings review mode defined
above.
FRM Frame:SF,ESF,UNFR,NONE Defines the type of frame pattern being received from the
DSX-1. Displayed during System Settings mode defined
above.
CODE Line Code: AMI, B8ZS This is the line code that the HLU is set to receive and
transmit at its DSX-1 interface. Displayed during System
Settings mode defined above.
LOSW Loss of Sync Word Indicates that the VHDSL loop has lost sync. Causes a
minor alarm.
LLOS Local Loss of Signal Indicates that no signal is detected at the T1 input to the
HLU. Causes a minor alarm.
RLOS Remote Loss of Signal Indicates that no signal is detected at the T1 input to the
HRU. Causes a minor alarm.
DS1 DS1 BPV errors Indicates that the number of BPVs at the HLU and HRU
DS1 inputs that have exceeded the 24 hour ES threshold.
Causes a minor alarm
DS0 DS0 Blocked Channels Indicates status of DS0 blocked channels. NONE indicates
no channels are blocked. BLK indicates some channels
are blocked.

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TABLE 4. HRU-612 STATUS MENU DEFINITIONS
Message Full Name Description
ALARMS
NONE No Alarms
LLOS Local Loss of Signal No signal from local T1 interface
RLOS Remote Loss of Signal No signal from remote T1 interface
MNR Minor Alrm A Minor Alarm condition is in effect.
LOSW Loss of Sync Word The VHDSL loops has lost sync.
HES VHDSL Loop Errored
Second The VHDSL CRC errors have exceeded the ES threshold
DS1 Digital Service 1 BPV’s have exceeded the ES threshold.
ACO Alarm Cut Off An Alarm Cut Off is in effect.
AIS Alarm Indicating Signal Indicates an AIS (all 1’s) pattern is being transmitted from the
local T1 output port.
LOOPBACKS
SMJK Smartjack Loopback Loopback at HRU towards network initiated by 2 in 5 in-band
loopback code or out-of-band ESF data link code. See Figure 5.
NREM Network Remote
Loopback Loopback at HRU (remote) towards network initiated from C.O. (network) by intelligent line repeater #1 code , HRU front panel
push-button or maintenance terminal . See Figure 5.
NLOC Network Local Loopback Loopback at HLU (local) towards network initiated from CO
(network) by intelligent office repeater code or by depressing
both the MODE & SEL HLU front panel pushbuttons. See Figure
5.
CLOC Customer Local Loopback Loopback at HRU (local) towards CI initiated from CPE
(customer) by intelligent line repeater #1 code . See Figure 5.
CREM Customer Remote
Loopback Loopback at HLU (remote) towards customer initiated from CPE (customer) by intelligent office repeater code . See Figure 5.
ARM Armed HiGain-2 has detected the intelligent repeater loopback (2 in 5)
arming code.
TLOS Transmit Loss of Signal HRU is in its TLOS initiated loopback state.

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TABLE 5. GLOSSARY OF HIGAIN TERMS
Term Definition
MARGINS Indicates the excess signal to noise ratio, at either the HLU or HRU, relative to a
10-7 Bit Error Rate. 1st value is current margin, 2nd value is minimum margin
since (C)leared last, 3rd value is maximum value since cleared. NA means Not
Available.
PULSE
ATTENUATION Indicates the attenuation of the 2B1Q pulse from the distant end. HiGain-2 operates with nominal pulse attenuations up to 28 dB. This value is related to the
cable pair’s 392 kHz loss. The pulse attenuation is a more direct indication of the
loop attenuation to the 2B1Q signal than the 392 kHz loss.
PPM Indicates the relative offset of the crystal oscillator in the HRU-612 from the HLU-
611’s crystal oscillator. Any value between -64 and +64 is adequate.
VHDSL 24 Hour ES
(Errored Seconds) The number of 1 second intervals that contained at least 1 CRC error. This value is a running total of the last 24 Hours.
VHDSL 24 Hour UAS
(Unavailable Seconds) The number of seconds the VHDSL loop was out of sync.
DS1 BPV Seconds
(ES) The number of seconds in which at least 1 bipolar violation was detected on the DS1 input.
DS1 UAS Count The number of seconds during which the DS1 input signal was absent (125 or more
consecutive 0’s)
Frame type Type of DS1 framing used on the input stream (SF, ESF, Unframed or No Activity)
Code type Type of DS1 line coding used (AMI, B8ZS, AMI : ZBTSI or B8ZS : ZBTSI). The
latter two conditions indicate the code type that is being received when HiGain-2 is
set to its ZBTS mode. In either the AMI or B8ZS DS1 code mode, it displays the
selected code as opposed to the code type that is actually being received.
Ver Vw.xL “w.x” = the software version number of the HLU
Vw.xR “w.x” = the software version number of the HRU.
yzL “yz” = List number of the HLU
yzR “yz” = List number of the HRU.

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Figure 7. HRU-612 Maintenance Terminal Main Menu.
Figure 8. HRU-612 View Span Status Display.

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Figure 9. HRU-612 System Settings Menu.
Figure 10. HRU-612 Set Clock Menu.

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Figure 11. HRU-612 View Performance Data Display.
Figure 12. HRU-612 View Performance History Display.

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Figure 13. HRU-612 View Alarm History Display.
Copyright © 1996, PairGain Technologies, Inc. PairGain is a registered trademark, CopperOptics and HiGain are trademarks of PairGain
Technologies, Inc.