ADTRAN E220/220 Maintenance and service guide

1Section 61245001L7-5, Issue 161245.001L7-5A
Section 61245001L7-5
Issue 1, May 1998
CLEI Code #T1L2BUCBAA
E220/220 T1 HTU-C
HDSL Transceiver Unit -- Central Office
INSTALLATION/MAINTENANCE
PRACTICES
C A U T I O N !
SUBJECT TO ELECTROSTATIC DAMAGE
OR DECREASE IN RELIABILITY.
HANDLING PRECAUTIONS REQUIRED.
1. GENERAL
TheADTRANE220/220LowVoltageHDSLTransceiver
Unit for the Central Office (HTU-C), part number
1245001L7, is the Central Office (CO) unit used to
deploy an HDSL T1 circuit using four-wire metallic
facilities. The unit occupies one slot in a standard 220
OfficeRepeaterBayortheADTRANE220Shelf. Figure
1 is an illustration of the ADTRAN HTU-C.
DSX-1 signals are provided to and received from the
network while 2B1Q HDSL signals are provided to the
local loop. The ADTRAN HTU-C works in conjunction
with the ADTRAN HTU-R and HRE to provide a DS1
service up to 24,000 feet on the local loop.
Trademarks:Anybrandnamesandproductnamesincludedinthisdocumentare
trademarks, registered trademarks, or trade names of their respective holders.
Figure 1. ADTRAN HTU-C
R
S
2
3
2
LP1
LP2
DSX
ALM
LBK
TX
RX
E
Q
DSX-1
LBO
B8ZS
FRM
ESF
NIU LB DIS
LBK TIMEOUT DIS
AMI
UFRM
SF
EN
EN
HTU-C
1245001L7
133 0
EXT
266
399
533
CONTENTS
1. GENERAL ...................................................................1
2. INSTALLATION...........................................................2
3. CONNECTIONS..........................................................4
4. HDSL SYSTEM TESTING ..........................................5
5. CONTROL PORT OPERATION .................................6
6. HDSL DEPLOYMENT GUIDELINES........................13
7. TROUBLESHOOTING PROCEDURES ...................13
8. MAINTENANCE ........................................................14
9. PRODUCT SPECIFICATIONS .................................14
10. WARRANTY AND CUSTOMER SERVICE ..............14
Appendix A. HDSL LOOPBACKS ..................................A-1
FIGURES
Figure 1. ADTRAN HTU-C..............................................1
Figure 2. HTU-C Edge Connector Wiring .......................4
Figure 3. HTU-C Span Powering Diagram .....................4
Figure 4. HTU-C Bantam Jack Arrangement .................5
Figure 5. HDSL Loopbacks.............................................5
Figure 6. RS-232 (DB9) Pin Assignments......................6
Figure 7. Introductory Menu Screen ...............................8
Figure 8. HDSL Main Menu Screen................................8
Figure 9. Current System Status Screen........................9
Figure 9A. Current System Status Screen - HRE.............9
Figure 10. Performance History Screen .........................10
Figure 10A. Performance History Screen - HRE ..............10
Figure 11. Loopback Options Screen .............................11
Figure 12. Self Test Options Screen ..............................11
Figure 13. Provisioning Screen ......................................12
Figure 14. Troubleshooting Display................................12
Figure 15. HDSL Deployment Guidelines ......................13
TABLES
Table A. Front Panel Rotary Switch Option Settings ....2
Table B. SW1 Option Settings .......................................3
Table C. Front Panel Indicators .....................................3
Table D. Screen Abbreviations ......................................6
Table E. HDSL Loss Values ........................................13
Table F. Loop Insertion Loss Data ..............................13
Table G. Troubleshooting Guide ..................................14
Table H. HDSL 220/E220 Low Voltage HTU-C
Specifications ................................................15
Table A-1. HDSL Enhanced Loopback Control
Codes ..........................................................A-1
Table A-2. Inband Addressable Loopback Codes ........A-2

2 Section 61245001L7-5, Issue 1 61245.001L7-5A
ThisHTU-CworkswithmultiplelistversionsoftheHDSL
unit remote end (HTU-R) and HDSL range extender
(HRE) as listed below:
• 1244041L2, Low Voltage T400 HRE
• 1244042L1, Low Voltage 819A HRE
• 1244044L1, Low Voltage 439 HRE
• 1245021L1, Low Voltage HTU-R T200 CP
• 1245022L1, Low Voltage HTU-R SA
• 1245026L1, Low Voltage HTU-R CI
The Low Voltage HTU-C can be deployed in circuits
consistingofoneHTU-CandoneHTU-R. Whendeployment
requires the HDSL Range Extender, the Low Voltage
HTU-CcanbedeployedwithoneLowVoltageHRE(T400
or 819A) and one Low Voltage HTU-R.
The HDSL local loop operates as two independent
subsystems each operating over a single twisted pair.
The HTU-C communicates over these two twisted pairs
to the HDSL Transceiver Unit Remote end (HTU-R).
Eachsubsystemcarrieshalfofthetotalbandwidthalong
with a small amount of overhead used for maintenance
and performance monitoring.
System power and alarm bus connections are made
throughthe backplane ofthe220 shelf. DSX-1andHDSL
signalsareconnectedthroughthewire-wrappinsorthe50
pin shelf connectors related to each individual slot.
The HTU-C contains onboard fuses. If a fuse opens, it
suppliesa–48VDCvoltagetothefusealarmbusandall
front panel indicators will be Off . These fuses are not
designed to be field replaceable.
The E220/220 Low Voltage HTU-C uses a DC-to-DC
converter to derive its internal logic and span powering
voltagesfrom the -48VDCoffice supply. The E220/220
LowVoltageHTU-CcanspanpowerHREsandHTU-Rs
aslistedabove. WhenusedwithLowVoltageHREsand
HTU-Rs, the HTU-C can span power the Low Voltage
HTU-R and Low Voltage HRE at less than –140 VDC.
Span powering voltages meet all requirements of Class
A3 voltages as specified by Bellcore GR-1089-CORE.
Revision History
This is the first issue of this practice. In subsequent
issues, changes will be summarized in this paragraph.
2. INSTALLATION
After unpacking the unit, inspect it for possible shipping
damage. Ifdamageisdiscovered,fileaclaimimmediately
withthecarrier,thencontactADTRANCustomerService
(see subsection 10).
The E220/220 Low Voltage HTU-C plugs directly into
standard 220 office repeater shelves. These include
Kentrox T-Term 220, Wescom 34220 and 34230, Lynch
303MA30 as well as the ADTRAN E220 Shelf and the
ADTRANE220RPShelf. Noinstallationwiringisrequired.
Onesix-positionrotaryswitch(RSW)andafive-position
dipswitch pack (SW1) accessible from the faceplate of
the unit are used to configure the mode of operation.
Figure 1 shows the location of these switches.
A definition of each switch is shown in Tables A and B.
Configuration may be performed by manually selecting
each option switch, or alternatively, may be performed
usingtheRS-232craftaccessport. Manualconfiguration
can be performed after installing the unit into the shelf.
Whentheunitispoweredup,changingasinglefaceplate
switchonlyaffectsthatsingleparameter. Whentheunit
is powered down, changing a single faceplate switch
causes a global reset to revert back to all faceplate
switch settings.
Craft interface allows configuration of DS0
Blocking and additional loopback timeout
settings.
Faceplate Indicators
The HTU-C has five faceplate LEDs which indicate
operational status. Table C defines these LEDs.
Table A. Front Panel Rotary Switch Option Settings 1
Switch Function Description
RSW DSX-1 Line Build-Out ....This rotary switch is used to select operation of the line build-out equalizer in series with the DSX-1 output.
EXT ................................Selects external line build-out 2
0 .................................Line length from 0-133 feet of ABAM cable
133 .................................Line length from 133-266 feet of ABAM cable
266 .................................Line length from 266-399 feet of ABAM cable
399 .................................Line length from 399-533 feet of ABAM cable
533 .................................Line length from 533-655 feet of ABAM cable
1The HTU-C transfers the local configuration to the HTU-R when circuit synchronization is achieved. The HTU-R then sets its configuration
to match the HTU-C.
2If external line build-out is selected, the signal transmitted by the HTU-C is a 12V p-p signal. This must be considered when measuring the
signal at the DSX EQ faceplate Bantam jack. The signal may appear hotter than it should be.

3Section 61245001L7-5, Issue 161245.001L7-5A
Description
Indicates five possible states of the quality of the HDSL signals on loop 1:
Off ................. No synchronization of HTU-C and HTU-R on loop 1.
Red ............... Poor signal quality on loop 1 (> 10-7 BER).
Yellow ........... Marginal signal quality on loop 1 (≤2 dB margin above 10-7 BER).
Green............ Good signal quality on loop 1 (> 2 dB margin above 10-7 BER).
Blinking ......... An error detected on either end of loop 1 will cause this LED to blink briefly.
Indicates five possible states of the quality of the HDSL signals on loop 2:
Off ................. No synchronization of HTU-C and HTU-R on loop 2.
Red ............... Poor signal quality on loop 2 (> 10-7 BER).
Yellow ........... Marginal signal quality on loop 2 (≤2 dB margin above 10-7 BER).
Green............ Good signal quality on loop 2 (> 2 dB margin above 10-7 BER).
Blinking ......... An error detected on either end of loop 2 will cause this LED to blink briefly.
Indicates the following three conditions:
Off ................. Network-side DSX-1 signal is absent or is of a format that does not match the
provisioning of the HDSL circuit.
Blinking ......... Bipolar Violation (BPV), frame bit error (SF mode), or CRC error (ESF mode)
detected at DSX-1 signal.
On Solid ........ Network-side DSX-1 signal is present and synchronized.
Indicates the following three conditions:
Off ................. No alarm condition detected.
Red ............... Alarm condition detected either locally (HTU-C), or locally and remotely (HTU-C and
HTU-R).
Yellow ........... Remote alarm condition detected.
Indicates three possible loopback states:
Off ................. Unit is not in loopback or armed state.
Blinking ......... The loopback arming sequence has been detected. In this state the unit is armed
(ready for loopback) but not in loopback.
On Solid ........ Local (HTU-C) loopback is active.
Table C. Front Panel Indicators
Indicator
LP1
LP2
DSX
ALM
LBK
Table B. SW1 Option Settings 1
(Default settings are indicated in bold typeface.)
Function
Loopback Timeout
Enabled
Disabled
NIU Loopback
Enabled
Disabled
Manual Frame Select
SF
ESF
T1 Framing
Unframed
Framed
Manual Code Select
AMI
B8ZS
1
The HTU-C transfers the local configuration to the HTU-R when circuit synchronization is achieved. The HTU-R then sets its
configuration to match the HTU-C.
2
Loopback timeout must be selected prior to initiating a loopback.
3
20-minutetimeoutisthedefaultforLoopbackTimeoutEnabled. 60-minuteand120-minutetimeoutsarealsoavailablefromthecraft
interface.
Description
Loopback Timeout is Enabled.2, 3
Loopback Timeout is Disabled.
This switch programs the ADTRAN HDSL system to respond to traditional T1 network interface
unit(NIU)loop-upandloop-downcodes. SeeAppendixAformoreinformationonspecificcodes.
Selects Superframe (SF) format.
Selects Extended Superframe (ESF) format.
This switch selects the T1 framing mode.
Selects Unframed (UFRM) operation; SW1-3 is ignored.
Selects Framed operation.
Alternate Mark Inversion (AMI) is selected.
B8ZS line code is selected.
Switch
SW1-1
SW1-2
SW1-3
SW1-4
SW1-5
HTU-C
1245001L7
TX
RX
LP1
LP2
DSX
ALM
LBK
R
S
2
3
2
B8ZS
FRM
ESF
NIU LB DIS
LBK TIMEOUT DIS
AMI
UFRM
SF
EN
EN
E
Q
DSX-1
LBO
533
399
266 133 0
EXT

4 Section 61245001L7-5, Issue 1 61245.001L7-5A
Figure 2. HTU-C Edge Connector Wiring
3. CONNECTIONS
The E220/220 Low Voltage HTU-C occupies one card
slot in a 220 Office Repeater Bay. Power and alarm
signals are provided to the card through the backplane
oftheshelf. DSX-1andHDSLloopsignalsareconnected
tothewire-wrappinsormassterminationshelfconnectors
corresponding to the slot the unit occupies. See Figure
2 for HTU-C edge connection wiring.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
Local RS485 +
-48 RET
Card Sense
Slot ID 1
Slot ID 2
Slot ID 3
Slot ID 4
Loop 1 HDSL Tip (Wire-Wrap)
Loop 1 HDSL Ring (Wire-Wrap)
Loop 2 HDSL Ring (Wire-Wrap)
Loop 2 HDSL Tip (Wire-Wrap)
-48V(1)
DSX-1 Rx Tip (Wire-Wrap)
DSX-1 Rx Ring (Wire-Wrap)
-48 RET
DSX-1 Tx Tip (Wire-Wrap)
DSX-1 Tx Ring (Wire-Wrap)
Local RS485 -
Active only
in ADTRAN
E220 Shelf
Fuse Alarm
Input to HTU-C
Output from HTU-C
Input to HTU-C
Output from HTU-C
The HTU-C is capable of span powering the HTU-R by
applying simplex current to the local loop. 30 to 155 m A
of current is coupled onto the HDSL span to power the
HTU-R and HRE when deployed. The span powering
voltageis lessthan –140volts with Loop 1 providingthe
negative voltage and Loop 2 the return (see Figure 3).
2B1Q
HDSL SPAN POWER
REGULATOR SPAN CURRENT
T (26)
R (27)
T1 (34)
R1 (35)
LOOP 1
LOOP 2
Figure 3. HTU-C Span Powering Diagram
HTU-C Alarm Outputs
Pin 32 of the HTU-C edge connector interface provides
a fuse alarm signal that connects –48 VDC to this pin in
thepresenceofablownfuse. Thisindicatesthecardhas
malfunctioned and should be replaced.
HFAC Alarm Outputs
If the HTU-C is operating in an ADTRAN E220 or E220
RPShelf with an HFAC(P/N1244051LX or equivalent),
the HTU-C provides information to the HFAC which is
used to generate alarms. The HFAC alarm outputs are
separate from the HTU-C alarm pin mentioned above.
For more information on the HFAC controlled alarms,
see the HFAC Installation and Maintenance practice,
section 61244051LX-5.

5Section 61245001L7-5, Issue 161245.001L7-5A
4. HDSL SYSTEM TESTING
The ADTRAN HDSL system provides the ability to
monitorthestatusandperformanceoftheDSX-1signals,
DS1 signals, and HDSL loop signals. Detailed
performance monitoring is provided by the faceplate
mounted RS-232 Control Port or the ADTRAN HDSL
Fuse/Alarm/ControlUnit(HFAC)ShelfController. These
features are valuable in troubleshooting and isolating
anysystemlevelproblemsthatmayoccuratinstallation
or during operation of the HDSL system. The following
subsections describe additional testing features.
HTU-C DSX EQ Bantam Jacks
The front panel of HTU-C contains metallic splitting
bantam jacks for access to DSX-1 Tx and Rx from the
local loop. This permits intrusive testing of the DSX-1
traffic on the HDSL local loop.
Figure4showsaccessprovidedbytheDSXEQbantam
jacks.
HTU-C
DATA
PUMP HDSL
SPAN POWER
DSX-1
T
R
DSX-1
T1
R1
HDSL
LOOP 1
HDSL
LOOP 2
HTU-C
HDSL
LOOP 1
HDSL
LOOP 2
EQ
RX
EQ
TX
Figure 4. HTU-C Bantam Jack Arrangement
HTU-C Loopbacks
TheHTU-Crespondstotwodifferentloopbackactivation
processes. First, loopback may be activated using the
craft interface. The Loopback Options Screen which
providesfortheHTU-C,HTU-R,andHREloopbackswill
be described in subsection 5.
Secondly, the HTU-C responds to the industry defacto
standard for HDSL loopbacks. A detailed description of
these loopback sequences is given in Appendix A.
Theloopback conditionimposed inboth cases is a logic
level loopback at the point within the HTU-C where the
DSX-1signalpasses into theHDSLmodulators. Figure
5 depicts all of the loopback locations possible with
ADTRAN HDSL equipment.
When the unit is selected for framing, the addressable
loopback codes will only be detected when sent in the
appropriateframingmode. Whentheunitisselectedfor
unframed, the addressable loopback codes will be
detected regardless of the framing mode in which they
are sent.
In addition to network-side loopbacks, the HTU-C
providescustomer-sideloopbacks initiated by usingthe
terminal control port. In this mode, either an AIS signal
or customer data is supplied to the network. Customer
sideloopbacksmustbedeactivatedbyusingtheterminal.
Figure 5. HDSL Loopbacks
DSX-1
HTU-C
LOCAL LOOP
HTU-C Network-Side Loopback
HTU-R
HTU-C
LOCAL LOOP
HTU-R Customer-Side Loopback
HTU-R
HTU-C
LOCAL LOOP
HTU-C Customer-Side Loopback
HTU-R
X
D
X
DS1
DSX-1
HTU-C
LOCAL LOOP
HTU-R Network-Side Loopback and/or
HTU-R NIU Loopback
HTU-R X
DS1
DS1
DS1
X = Signal Inactive
D = Data Sent
X
AIS
D
AIS
HTU-C
HRE Network-Side Loopback
HTU-R
DS1
DSX-1
HRE
AIS
X
X

6 Section 61245001L7-5, Issue 1 61245.001L7-5A
5. CONTROL PORT OPERATION
TheHTU-Cprovidesafaceplate-mountedDB9connector
that supplies an RS-232 interface for connection to a
controlling terminal. The pinout of the DB9 is illustrated
in Figure 6.
running on the personal computer. If using a portable
personal computer with terminal emulation capability,
communication between the computer and the HDSL
unit may be periodically disrupted if power saving
programs are being used on the personal computer.
The symptoms may include misplaced characters
appearingonthescreenand/ortheoccurrenceofscreen
timeouts. These symptoms are not disruptive to the
operation of the circuit and are avoidable if the power
saving options are disabled or removed.
WhenoperatingtheunitintheADTRANE220Shelf
with an HFAC (HDSL shelf controller), all remote
terminaloperationmustbemadethroughthecontrol
port of the shelf controller, not the HTU-C.
Operation
For abbreviations used in the screen diagrams, see
Table D.
ThescreensillustratedinFigures7through14areforan
HDSL circuit deployed with ADTRAN’s Low Voltage
HDSL technology. The circuit includes an HTU-C,
Figure 6. RS-232 (DB9) Pin Assignments
Table D. Screen Abbreviations
Abbreviation
ES
SES
UAS
SF
ESF
B8ZS
AMI
LBO
BPV
NIU
S/N
15M
24H
Definition
Errored Seconds
DSX/DS1 .................. SF: Second in which a BPV or frame bit error occurs.
ESF: Second in which a BPV or CRC error occurs.
HDSL ........................ Second in which a CRC error occurs.
Severely errored seconds.
DSX/DS1 .................. SF: Second in which 1544 BPVs or 8 frame bit errors occurs.
ESF: Second in which 1544 BPVs or 320 CRC errors occur.
HDSL ........................ Second in which 165 CRC errors occurs.
Unavailable seconds
DSX/DS1 .................. Second in which there is a loss of signal or sync.
HDSL ........................ Second in which there is a loss of signal or sync.
Superframe format.
Extended superframe format.
Binary 8 zero substitution.
Alternate mark inversion.
Line build-out.
Bipolar violation.
DSX/DS1 .................. Second in which a bipolar violation occurs.
T1 Network Interface Unit.
Serial number.
Fifteen-minute period.
Twenty-four-hour period.
The terminal interface operates at data rates from 1.2
kbps to 19.2 kbps. The asynchronous data format is
fixed at 8 data bits, no parity, and 1 stop bit. The
supported terminal type is VT 100 or compatible.
Many portable personal computers use power-saving
programs that are known to interfere with applications
6
7
8
9
1
2
3
4
5
TXD (Transmit Data)
RXD (Receive Data)
SGN (Signal Ground)

7Section 61245001L7-5, Issue 161245.001L7-5A
HTU-R, and HRE. This scenario was chosen for
inclusiveness of functionality. However, other
configurations are possible and their displays will vary
slightly from those shown in this section.
Aterminal sessionis initiated byentering multiple space
barcharacters,whichareusedbytheHTU-Ctodetermine
the speed of the terminal. Once the speed has been
determined, an Introductory Menu is presented, as
illustrated in Figure 7.
From the Introductory Menu, the Main Menu may be
selected. The Main Menu provides access to detailed
performanceandconfigurationinformation,asillustrated
in Figure 8, HDSL Main Menu Screen.
From the Main Menu, the following screens can be
accessed.
1. Current System Status
2. Performance History
3. ADTRAN Information
4. Loopback Options
5. Self Test
6. Provisioning
7. Troubleshooting
TheCurrentSystemStatusscreenillustratedinFigure9
provides quick access to status information for both the
HTU-C and HTU-R. By pressing H, the Current System
Status screen for the HRE will be displayed. See Figure
9A for the HRE Current System Status screen.
The Elapsed Time display indicates the period of time
sincetheunitbegancollectingperformanceinformation.
Ateach 15-minute interval,theperformance information
istransferredtothe15-minuteperformancedataregister
accessedfromthePerformanceHistoryscreen. Ateach
24-hourinterval,theperformancedataistransferredinto
the 24-hour performance data register also accessed
usingthePerformanceHistoryscreen. ThePerformance
HistoryscreenisshowninFigure 10. By pressing H, the
PerformanceHistoryscreenfortheHREwillbedisplayed.
SeeFigure10AfortheHREPerformanceHistory screen.
By pressing the letter Zat the Current System Status
screen,thecurrentperformanceregisterswillberesetto
zero on the Current System Status screen and
Performance History screen.
Figures 9 and 9A consolidate current information for the
HDSL,DSX-1,andDS1interfaces. Akeytotheinformation
provided is found in the center of the screen. Arrows
indicate the key applies to both the HTU-C and HTU-R.
LOSS ................. Pulse Attenuation Measurement *
* LOSS is typically several dB less than the insertion loss
measured at 200 kHz. The LOSS measurement is a better
indication of the loop’s attenuation of the 2B1Q signal than the
insertion loss measured at a single frequency. Adtran HDSL
can operate on cables with an excess of 30 dB LOSS.
SYNC................. HDSL Loop 1 and Loop 2 Sync Status
ES 15M/24H ...... Errored Seconds*
SES 15M/24H.... Severely Errored Seconds*
UAS 15M/24H.... Unavailable Seconds*
* Thefirstnumberis forthecurrent15-minute period and
the second is the current 24-hour period (Loop 1 and
Loop 2 numbers are displayed).
An indication of Pair Reversal (if present) is given at the
bottomof thefirst key column. Statusand configuration
information for the DS1 and DSX-1 signals is located in
the center of the screen near the bottom.
FRAME ....... T1 Framing Format selected
CODE .........T1 Line Code selected
LBO............. Line Build-Out selected (for DSX-1);
Customer Signal of 0 or –15 dB (for DS1)
NIU.............. Network Interface Unit enabled?
BPV ............. Bipolar Violations detected (DSX-1 and DS1)
ES ...............Errored Seconds (DSX-1 and DS1)
SES............. Severely Errored Seconds (DSX-1 and DS1)
UAS ............ Unavailable Seconds (DSX-1 and DS1)
Alarms.........Lists current alarm condition status
A measure of signal quality for each HDSL loop is
displayed in graphic form on the bottom of the screen.
Themeasureisfrom0(poorsignalquality)to9(excellent
signalquality). Guidelinesforinterpretingtheindicators
are given below.
0 ......... Noise margin is ≤0 dB (≈10-7 BER)
1-8...... Margin measurement above 10-7 BER in dB
9 ......... Margin is ≥9 dB (excellent quality) above 10-7
BER
Predictingperformancebaseduponsignalqualityvaries
with each loop. Generally, a noise margin of 0 or higher
will support a bit error rate of better than 10-7. ADTRAN
has defined the following as guidelines that correspond
to the operation of the HTU-C faceplate LEDs labeled
LP1 and LP2.
Margin < 0 ( Red) ....................Poor Loop Quality
0 ≤Margin ≤2 (Yellow) ...........Marginal Loop Quality
Margin > 2 (Green)..................Good Loop Quality
Figures 11 and 12 depict the HDSL Loopback and Self
Test Option screens. Loopbacks and Self-Test may be
evoked or terminated using these screens. A status of
current loopback conditions is also provided.
Figure13displayscurrentprovisioningsettingsandallows
forchangingthesystemconfiguration. Provisioningchanges
are only allowed at the CO end of the circuit. Provisioning
changes made through this screen override the manual
switch settings. The unit retains the last provisioning
changes to determine its operating mode.

8 Section 61245001L7-5, Issue 1 61245.001L7-5A
TheDS1OutputLeveloptionintheProvisioning
Screen of the HTU-C can only be altered if the
circuitcontainsa2ndor 4th generationHTU-R.
(The generation of the product is identified in
the fourth digit of the product number.)
The Troubleshooting Display, shown in Figure 14,
graphically presents an HDSL circuit. The unit reviews
red, yellow, and blue alarm conditions in the circuit to
automatically predict where a fault is located. Once a
fault location is suspected, the corresponding portion of
the circuit on the screen is highlighted and a message
describing the failure is presented.
Figure 8. HDSL Main Menu Screen
ADTRAN HDSL MAIN MENU
1) CURRENT SYSTEM STATUS
2) PERFORMANCE HISTORY
3) ADTRAN INFORMATION
4) LOOPBACK OPTIONS
5) SELF-TEST
6) PROVISIONING
7) TROUBLESHOOTING
Choose a screen by pressing the corresponding number.__
__
_
Figure 7. Introductory Menu Screen
ADTRAN
901 Explorer Boulevard
Huntsville, Alabama 35806-2807
For Information or Technical Support,
Normal Support Hours ( 7am - 7pm CST ) or Emergency Support Hours ( 7x24 )
Voice Toll Free: 800.726.8663 Fax: [phone]
Voice: 205.963.8100 Internet: www.adtran.com
———————————————————————————————————————----------------------------------------
HTU-C INFORMATION SIGNAL QUALITY HTU-R INFORMATION SIGNAL QUALITY
——————————---------- [X] 9 [X] ——————————---------- [X] 9 [X]
S/N : L[X] 8 L[X] S/N : L[X] 8 L[X]
CLEI: O[X] 7 O[X] CLEI: O[X] 7 O[X]
MANF: / O[X] 6 O[X] MANF: O[X] 6 O[X]
P[X] 5 P[X] P[X] 5 P[X]
HRE #1 INFORMATION [X] 4 [X] [X] 4 [X]
——————————---------- 1[X] 3 2[X] 1[X] 3 2[X]
S/N : [X] 2 [X] [X] 2 [X]
CLEI: [X] 1 [X] [X] 1 [X]
MANF: / [X] 0 [X] [X] 0 [X]
AT HTU-C AT HTU-R
Press “M” to view Main Menu.

9Section 61245001L7-5, Issue 161245.001L7-5A
Figure 9. Current System Status Screen
HTU-C CURRENT SYSTEM STATUS HTU-R
LOOP #1 <NETWORK> LOOP #2 ELAPSED TIME 00:00:09 LOOP #1 <CUSTOMER> LOOP #2
-------------------------- ---------------------------
01 dB 01 dB <- LOSS -> 01 dB 01 dB
YES YES <- SYNC -> YES YES
000/00000 000/00000 <- ES 15M/24H -> 000/00000 000/00000
000/00000 000/00000 <- SES 15M/24H -> 000/00000 000/00000
000/00000 000/00000 <- UAS 15M/24H -> 000/00000 000/00000
LOOPBACKS INACTIVE LOOPBACKS INACTIVE
HTU-C SIGNAL QUALITY DSX-1 DS1 HTU-R SIGNAL QUALITY
[X] 9 [X] --------------------------- [X] 9 [X]
L[X] 8 L[X] ESF <- FRAME -> ESF L[X] 8 L[X]
0[X] 7 0[X] B8ZS <- CODE -> B8ZS 0[X] 7 0[X]
0[X] 6 0[X] 0-133 <- LB0 -> 0 dB 0[X] 6 0[X]
P[X] 5 P[X] N/A <- NIU -> YES P[X] 5 P[X]
[X] 4 [X] 00000 <- BPV -> 00000 [X] 4 [X]
1[X] 3 2[X] 00000 <- ES -> 00000 1[X] 3 2[X]
[X] 2 [X] 00000 <- SES -> 00000 [X] 2 [X]
[X] 1 [X] 00000 <- UAS -> 00000 [X] 1 [X]
[X] 0 [X] NONE <- ALARMS -> NONE [X] 0 [X]
SEALING CURRENT PRESENT
Press “Z” to zero registers, “M” for Main Menu,
“H” for HDSL Range Extender #1 (HRE) View.
Figure 9A. Current System Status Screen - HRE
HRE #1 CURRENT SYSTEM STATUS HRE #1
LOOP #1 <NETWORK> LOOP #2 ELAPSED TIME 00:00:03 LOOP #1 <CUSTOMER> LOOP #2
-------------------------- ---------------------------
01 dB 01 dB <- LOSS -> 01 dB 01 dB
YES YES <- SYNC -> YES YES
000/00000 000/00000 <- ES 15M/24H -> 000/00000 000/00000
000/00000 000/00000 <- SES 15M/24H -> 000/00000 000/00000
000/00000 000/00000 <- UAS 15M/24H -> 000/00000 000/00000
LOOPBACKS INACTIVE
HRE NET SIGNAL QUALITY N = NETWORK SIDE RECEIVER HRE CUST SIGNAL QUALITY
[X] 9 [X] C = CUSTOMER SIDE RECEIVER [X] 9 [X]
L[X] 8 L[X] L[X] 8 L[X]
0[X] 7 0[X] ____ ____ ____ 0[X] 7 0[X]
0[X] 6 0[X] |HTUC| LOOP1 |HRE1| LOOP1 |HTUR| [X] 6 0[X]
P[X] 5 P[X] | |========N| |C========| | P[X] 5 P[X]
[X] 4 [X] | | | | | | [X] 4 [X]
1[X] 3 2[X] | |========N| |C========| | 1[X] 3 2[X]
[X] 2 [X] |____| LOOP2 |____| LOOP2 |____| [X] 2 [X]
[X] 1 [X] [X] 1 [X]
[X] 0 [X] [X] 0 [X]
Press “Z” to zero registers, “M” for Main Menu,
“P” for previous view.

10 Section 61245001L7-5, Issue 1 61245.001L7-5A
Figure 10. Performance History Screen
Figure 10A. Performance History Screen - HRE
PERFORMANCE HISTORY <VIEW 1 - HTU-C DSX-1 RECEIVER>
24 HOUR REGISTERS 15 MINUTE REGISTERS
---ES---SES-- --ES-SES----------ES-SES-
00000 00000 <---CURRENT---> 000 000
-1: ----- ----- <-- --> -1: 000 000 -17: 000 000
-2: ----- ----- | | -2: 000 000 -18: 000 000
-3: ----- ----- | | -3: 000 000 -19: 000 000
-4: ----- ----- | | -4: 000 000 -20: 000 000
-5: ----- ----- |PREVIOUS | -5: 000 000 -21: 000 000
-6: ----- ----- | | -6: 000 000 -22: 000 000
-7: ----- ----- <-- | -7: 000 000 -23: 000 000
| -8: 000 000 -24: 000 000
VIEW LOCATION DIAGRAM | -9: 000 000 -25: 000 000
| -10: 000 000 -26: 000 000
1->|H|<-3------|H|------4->|H|--> | -11: 000 000 -27: 000 000
|T| |R| |T| | -12: 000 000 -28: 000 000
|U| |E| |U| | -13: 000 000 -29: 000 000
<--|C|<-5------|1|------6->|R|<-2 | -14: 000 000 -30: 000 000
| -15: 000 000 -31: 000 000
--> -16: 000 000 -32: 000 000
Press view number to select view, “M” to return to Main Menu
Press “H” to view HRE #1 history
PERFORMANCE HISTORY <VIEW 1 - HRE NETWORK LP1 RECEIVER>
24 HOUR REGISTERS 15 MINUTE REGISTERS
---ES---SES-- --ES-SES----------ES-SES-
00000 00000 <---CURRENT---> 000 000
-1: ----- ----- <-- --> -1: 000 000 -17: 000 000
-2: ----- ----- | | -2: 000 000 -18: 000 000
-3: ----- ----- | | -3: 000 000 -19: 000 000
-4: ----- ----- | | -4: 000 000 -20: 000 000
-5: ----- ----- |PREVIOUS | -5: 000 000 -21: 000 000
-6: ----- ----- | | -6: 000 000 -22: 000 000
-7: ----- ----- <-- | -7: 000 000 -23: 000 000
| -8: 000 000 -24: 000 000
VIEW LOCATION DIAGRAM | -9: 000 000 -25: 000 000
| -10: 000 000 -26: 000 000
-->|H|<-----1->|H|-2------>|H|--> | -11: 000 000 -27: 000 000
|T| |R| |T| | -12: 000 000 -28: 000 000
|U| |E| |U| | -13: 000 000 -29: 000 000
<--|C|<-----3->|1|-4------>|R|<-- | -14: 000 000 -30: 000 000
| -15: 000 000 -31: 000 000
--> -16: 000 000 -32: 000 000
Press view number to select view, “M” to return to Main Menu
Press “P” for previous view

11Section 61245001L7-5, Issue 161245.001L7-5A
Figure 11. Loopback Options Screen
LOOPBACK OPTIONS
_____ _____ _____
|HTU-C| |HRE 1| |HTU-R|
| | | | | |
| | LP1 | | LP1 | |
--->|-----|<=========>| |<=========>|-----|<---
| | | | | |
NET| | | | | |CUST
| | LP2 | | LP2 | |
<---|-----|<=========>| |<=========>|-----|<---
| | | | | |
| | | | | |
|_____| |_____| |_____|
1) LOOPBACK TO NETWORK AT HTU-C = INACTIVE
2) LOOPBACK TO CUSTOMER AT HTU-C = INACTIVE
3) LOOPBACK TO NETWORK AT HTU-R = INACTIVE
4) LOOPBACK TO CUSTOMER AT HTU-R = INACTIVE
5) LOOPBACK TO NETWORK AT HRE1 = INACTIVE
Press corresponding number to toggle loopback option.
Press “M” for Main Menu.
Figure 12. Self Test Options Screen
SELF-TEST
Press “S” to initiate HTU-C and HTU-R self-tests.__
__
_
Press “M” to return to the Main Menu.

12 Section 61245001L7-5, Issue 1 61245.001L7-5A
Figure 13. Provisioning Screen
Figure 14. Troubleshooting Display
TROUBLESHOOTING DISPLAY
_____ _____ _____
|HTU-C| |HRE 1| |HTU-R|
| | | | | |
| | | | | |
--->|-----|<=========>| |<=========>|-----|<---
| | | | | |
NET| | | | | |CUST
| | | | | |
<---|-----|<=========>| |<=========>|-----|<---
| | | | | |
| | | | | |
|_____| |_____| |_____|
NO ALARM CONDITIONS
Press “M” for Main Menu.
PROVISIONING
________________________________________________ ______________________
| | |
| PROVISIONS CURRENT SETTINGS | HARDWARE SETTINGS |
| ——————————————————---------------------——— | ————————--------- |
| 1. DSX-1 LINE BUILDOUT = 0-133 FEET | 0-133 FEET |
| 2. DSX-1/DS1 LINE CODE = B8ZS | B8ZS |
| 3. DSX-1/DS1 FRAMING = ESF | ESF |
| 4. NIU LOOPBACK = ENABLED | ENABLED |
| 5. LOOPBACK TIMEOUT = 20 MIN | 20 MIN |
| 6. DS1 TX LEVEL = 0 dB | |
| 7. DS0 BLOCKING | |
| | |
| 00000000 00000000 00000000 | |
| CHANNELS 1 24 | |
| “X” INDICATES A BLOCKED CHANNEL.| |
|________________________________________________|______________________|
Press: “n” — to change corresponding provision (ex. “3” for FRAMING)
“H” — to copy hardware settings to current settings
“I” — to implement and save current setting changes
“M” — to return to the main menu

13Section 61245001L7-5, Issue 161245.001L7-5A
Figure 15. HDSL Deployment Guidelines
6. HDSL DEPLOYMENT GUIDELINES
TheADTRANHDSLsystemisdesigned to provide DS1
based services over loops designed to comply with
carrierservicearea(CSA)guidelines. CSAdeployment
guidelines are given below.
1. All loops are non-loaded only.
2. For loops with 26-AWG cable, the maximum
looplengthincludingbridgedtaplengthsis9kft.
3. For loops with 24-AWG cable, the maximum
loop length including bridged tap lengths is
12 kft.
4. Any single bridged tap is limited to 2 kft.
5. Total bridged tap length is limited to 2.5 kft.
6. Thetotallengthofmulti-gaugecablecontaining
26-AWG cable must not exceed the following:
12 - {(3*L26)/9} - LBTAP (in kft)
L26 = Total length of 26-AWG cable excluding
bridged taps (in kft)
LBTAP = Total length of all bridged taps (in kft)
This deployment criteria is summarized in the chart
shown in Figure 15.
LooplossperkftforotherwireissummarizedinTableE.
Table E. HDSL Loss Values
(200 kHz cable loss in dB/kft at 135 Ω )
___________________________________________
Cable Cable Temperature:
Gauge Type 68°90°120°
___________________________________________
26 ............. PIC ........... 3.902.... 4.051 ... 4.253
26 ............. Pulp .......... 4.030.... 4.179 ... 4.381
24 ............. PIC ........... 2.863.... 2.957 ... 3.083
24 ............. Pulp .......... 3.159.... 3.257 ... 3.391
22 ............. PIC ........... 2.198.... 2.255 ... 2.333
22 ............. Pulp .......... 2.483.... 2.45 ..... 2.629
19 ............. PIC ........... 1.551.... 1.587 ... 1.634
19 ............. Pulp .......... 1.817.... 1.856 ... 1.909
___________________________________________
Recommendedmaximumlocallooplossinformationfor
PICcableat70°F,135Ω,resistiveterminationisprovided
in Table F.
Table F. Loop Insertion Loss Data
________________________________
Frequency (Hz) Maximum Loss (dB)
________________________________
3,000 ......................... 12.0
10,000 ......................... 15.0
50,000 ......................... 25.5
100,000 ......................... 30.0
150,000 ........................ 32.75
200,000 ........................ 35.25
________________________________
Anapproximationforthemaximumamountofwideband
noise on an HDSL local loop as measured by a 50 kbps
filter is ≤31 dBrn.
An approximation for the maximum level of impulse
noise as measured using a 50 kbps filter on an HDSL
loop is ≤50 dBrn.
These approximations are to be used as
guidelinesonlyandmayvaryslightlyondifferent
loops. Adheringtotheguidelinesshouldproduce
performance in excess of 10
-7
BER.
7. TROUBLESHOOTING PROCEDURES
0
12
11
10
9
8
7
6
5
4
3
2
1
01234
WORKING LENGTH OF 26 GAUGE CABLE (KFT)
WORKING LENGTH OF 24 GAUGE (OR COARSER) CABLE (KFT)
56789
2.5
INVALID HDSL CABLE LENGTHS
2.0 1.5 1.0 0.5 0.0
TOTAL
BRIDGED
TAPLENGTH
(KFT)
VALID HDSL CABLE LENGTHS

14 Section 61245001L7-5, Issue 1 61245.001L7-5A
Table G. Troubleshooting Guide
Solution
1. Verify that –48 VDC power is properly
connected to the shelf.
2. Insert the HTU-C into an operational
slot and check the LED indicators.
When the unit is powered, at least one
LED will be on.
3. Ifstep1passes,butstep2fails,replace
the HTU-C.
See Table C on page 3 for information
regarding the state of the circuit as
describedbythefront panel indicators.
Condition
All front panel
indicators are off.
Other
TableGisatroubleshootingguidefortheE220/220Low
Voltage HTU-C.
8. MAINTENANCE
The ADTRAN E220/220 Low Voltage HTU-C requires
no routine maintenance. In case of equipment
malfunction, use the faceplate Bantam jack connectors
to help locate the source of the problem.
ADTRANdoesnotrecommendthatrepairsbeperformed
inthefield.Repairservicesmaybeobtainedbyreturning
the defective unit to the ADTRAN Customer Service
RMA Department.
9. PRODUCT SPECIFICATIONS
Product specifications are detailed in Table H.
10. WARRANTY AND CUSTOMER SERVICE
ADTRAN will replace or repair this product within ten
years from the date of shipment if it does not meet its
published specifications or fails while in service (see
ADTRANEquipmentWarranty,Repair,andReturnPolicy
and Procedure).
Return Material Authorization (RMA) is required prior to
returning equipment to ADTRAN.
Forservice,RMArequests,orfurtherinformation,contact
one of the following numbers.
ADTRAN Customer Service:
ADTRAN Telco Technical Support ..... [phone]
Standard support hours: ......................Monday-Friday
7 a.m. - 7 p.m. CST
Emergency support:..........7 days/week, 24 hours/day
Sales ................................................... [phone]
RMA (repair service)........................... [phone]
Repair and Return Address:
ADTRAN, Inc.
Customer Service Department
901 Explorer Boulevard
Huntsville, Alabama 35806-2807

15Section 61245001L7-5, Issue 161245.001L7-5A
Loop Interface
Modulation Type: ............................................... 2B1Q
Mode: ................................................................. Full Duplex, Echo Cancelling
Number of Pairs: ................................................ Two
Bit Rate: ............................................................. 784 kbps per pair
Baud Rate: ......................................................... 392K baud per pair
Service Range: .................................................. Defined by Carrier Service Area Guidelines
Loop Loss:.......................................................... 36 dB maximum @ 200 kHz
Bridged Taps:..................................................... Single Taps < 2000 feet, Total Taps < 2500 feet
Performance: ..................................................... Compliant with Bellcore TA-NWT-001210
HDSL Tx Signal Level: ...................................... 13.5 dBm
Input Impedance: ............................................... 135Ω
Return Loss:....................................................... 20 dB (40 kHz to 200 kHz)
Network Interface
4-WIRE DSX-1
DSX-1 Output Level:.......................................... 0 dB
DSX-1 Line Build Out:........................................ 0-133 feet ABAM
134-266 feet ABAM
267-399 feet ABAM
400-533 feet ABAM
534-655 feet ABAM
DSX-1 Line Code: .............................................. AMI, B8ZS
DSX-1 Format: ................................................... SF, ESF, Unframed
DSX-1 Channelization: ...................................... Channels 1-12 on HDSL Loop 1, Channels 13-24 on HDSL Loop 2
Power
Tested with the ADTRAN Low-Voltage HRE (P/N 1244.042L1) and the ADTRAN Low Voltage HTU-R (1245.021L1).
Total Power: .......................................................... -48 VDC @ 180 m A with HTU-R
-48 VDC @ 370 m A with HTU-R and HRE
HTU-C Power Dissipation: .................................... 5 watts with HTU-R
6 watts with HRE and HTU-R
Span Power: .......................................................... <-140 VDC (Internally Generated) current limited at 150 m A
Fusing: ................................................................... 1.00 A BUSS GMT-1.00 or equivalent (not field replaceable)
Clock
Clock Sources:................................................... Internal, DSX-1 Derived
Internal Clock Accuracy:.................................... ±25 ppm (exceeds Stratum 4). Meets T1.101 timing requirements.
Tests
Diagnostics: ....................................................... Self-Test, Local Loopback (HTU-C), Remote Loopback (HTU-R)
Physical
23" 220 Office Repeater Shelf-Mounted
Dimensions: ....................................................... 5.6" High x 1.25' Wide x 10.1" Deep
Weight: ............................................................... Less than 1 lb.
Environment
Temperature: ..................................................... Operating (Standard): -40°to +70°C Storage: -40°to +85°C
Control Port
Interface: ............................................................ RS-232 (DB9)
Terminal Type: ................................................... VT 100 or compatible
Async Speed:..................................................... 1.2 kbps to 19.2 kbps
Data Format: ...................................................... 8 data bits, no parity, 1 stop bit
Part Number
HTU-C 220/E220 Circuit Pack........................... 1245001L7
Table H. HDSL 220/E220 Low Voltage HTU-C Specifications

61245.001L7-5A Section 61245001L7-5, Issue 1 A-1
HDSL MAINTENANCE MODES
ThisappendixdescribesoperationoftheHDSLsystem
with regard to detection of in-band and ESF facility
data link loopback codes.
Upon deactivation of a loopback, the HDSL system
will synchronize automatically. Note that the
synchronization process of the HDSL system upon
deactivation of the HRE loopback could take up to 15
seconds, ensuring all system elements are
synchronized.
Loopback Process Description
Ingeneral,theloopbackprocessfortheHDSLsystem
elementsismodeledonthecorrespondingDS1system
process. Specifically, the HTU-C loopback is similar
to an Intelligent Office Repeater loopback and the
HTU-Rloopbacksaresimilartoaninline T1Repeater
loopback.
In-band control code sequences are transmitted over
the DS1 link by either the unframed or overwrite
method. TheHDSLelementsrespondtoeithermethod.
The unframed method produces periodic control
sequencesandthenormalDS1framingbitisomitted.
Appendix A
HDSL LOOPBACKS
The overwrite method produces periodic control
sequences. However,onceper frame, the framingbit
overwrites one of the bits in the control sequence.
The unit can detect the loopback activation or
deactivation code sequence only if an error rate of
1E-03 or better is present.
DDS Latching Loopback Operation
IftheunitisoptionedforFT1mode,thenDDSLatching
Loopback operation is supported as described in
BellcoreTA-TSY-000077,Issue3,Section5.1.3. The
HTU-C and any HRE units which are in the HDSL
circuit are treated as Identical Tandem Dataports and
theHTU-R istreated as aDifferent TandemDataport.
For a complete description of the DDS Latching
Loopback codes, refer to Bellcore TA-TSY-000077,
Issue 3, Section 5.1.3.
Loopback Control Codes
AsummaryofcontrolsequencesisgiveninTablesA-1
and A-2.
In all control code sequences presented, the
in-band codes are shown left-most bit
transmittedfirst, and the ESF datalink codes
with right-most bit transmitted first.
Table A-1. HDSL Enhanced Loopback Control Codes
Type Source Code Name
(N) 3in7 (1110000) ...... Loopback data from network toward network in the HTUR.
(N) 4in7 (1111000) ...... Loopback data from network toward network in the HTUC.
Abbreviated (N) 2in6 (110000) ........ Loopback data from network toward network in first HRE.
(C ) 6in7 (1111110) ...... Loopback data from customer toward customer in HTUC.
(C ) 5in7 (1111100) ...... Loopback data from customer toward customer in HTUR.
(C ) 4in6 (111100) ........ Loopback data from customer toward customer in first HRE.
(N) FF1E ...................... Loopback data from network toward network at HTUC.
(C) 3F1E ...................... Loopback data from customer toward customer at HTUC.
(N) FF04 ...................... Loopback data from network toward network at HRE1.
(C) 3F04 ...................... Loopback data from customer toward customer at HRE1.
Wescom (N) FF02 ...................... Loopback data from network toward network at HTUR.
(C) 3F02 ...................... Loopback data from customer toward customer at HTUR
(N) 1in6 (100000) ........ Loopback data from network toward network at HTUR.
(N) FF48 (ESF-DL) ...... Loopback data from network toward network at HTUR.
(N/C) 1in3 (100) .............. Loopdown everything.
(N/C) FF24 (ESF-DL) ...... Loopdown everything.
Notes: The Source column indicates which side of the interface the control codes are sent from.
For example, an (N) indicates a network sourced code while a (C) indicates a customer
sourced code.
All codes are inband unless labeled ESF-DL.
All codes listed above must be sent for a minimum of 5 seconds in order for them to be
detected and acted upon.

A-2 Section 61245001L7-5, Issue 1 61245.001L7-5A
Table A-2. Inband Addressable Loopback Codes
FUNCTION CODE
ARM ............................................................... 11000
(also known
as a 2-in-5
pattern)
DISARM ......................................................... 11100
(also known
as a 3-in-5
pattern)
HTU-C NETWORK LOOPUP........................ D3D3
(1101 0011
1101 0011)
HRE NETWORK LOOPUP ........................... C741
(1100 0111
0100 0001)
LOOPDOWN ................................................. 9393
(1001 0011
1001 0011)
QUERY LOOPBACK ..................................... D5D5
(1101 0101
1101 0101)
LOOPBACK TIMEOUT OVERRIDE ............. D5D6
(1101 0101
1101 0110)
SPAN POWER DISABLE .............................. 6767
(0110 0111
0110 0111)
RESPONSE
NIULOOPBACKENABLED: TheHTU-Rwillloopuptowardsthenetwork.
No AIS or errors will be sent as a result of this loopback. The HTU-C and
HRE will ARM.
TheHTU-CandHREareremovedfromthearmedstate. Ifanyoftheunits
are in loopback when the 11100 pattern is received, they will loopdown.
The LBK LEDs will turn off on all units.
Iftheunitshavebeenarmedandnounitsareinloopback*,theHTU-Cwill
loopup towards the network, 2 seconds of AIS (all 1s) will be sent, 5
seconds of data will pass, and then 231 bit errors will be injected into the
DSX-1signal. As longas the patterncontinues tobesent, 231errors will
be injected every 20 seconds. When the pattern is removed, the unit will
remain in loopback. If the pattern is reinstated, the injection of 231 bit
errors will resume at 20 second intervals.
IfanHREispresent,theunitshavebeenarmed,theHREwillloopup
towardsthenetwork,2secondsofAIS(all1s)willbesent,5secondsof
datawillpass,andthen10biterrorswillbeinjectedintotheDSX-1signal.
Aslongasthepatterncontinuestobesent,10errorswillbeinjectedevery
20seconds.Whenthepatternisremoved,theunitwillremainin
loopback.Ifthepatternisreinstated,theinjectionof10biterrorswill
resumeat20secondintervals.
AnyHTU-CandHREunitscurrentlyinloopbacktowardsthenetworkwill
loopdownandwillnotattainthearmedstate.
IftheunitsarearmedandtheHTU-C,HRE,orHTU-Rareinnetwork
loopback,errorsareinjectedintotheDSX-1signalupondetectionofthe
queryloopbackpattern.Aslongasthepatterncontinuestobesent,
errorsareinjectedagainevery20seconds.Thenumberoferrors
injectedeachtimedependsonwhichunitisinloopback.231errorsare
injectediftheHTU-Cisinnetworkloopback,20atatimeiftheHTU-Ris
innetworkloopback,and10atatimeiftheHREisinnetworkloopback.
Iftheunitsarearmedandthispatternissent,theloopbacktimeoutwillbe
disabled.ThetimeoutoptionwillbeupdatedonthePROVISIONING
menuoftheHTU-R(viewablethroughtheRS-232port)toNONE.Aslong
astheunitsremainarmed,thetimeoutwillremaindisabled.Whenthe
unitsaredisarmed,theloopbacktimeoutwillreturntothevalueithad
beforetheD5D6codewassent.
Iftheunitsarearmedandthispatternissent,theHTU-Cwilldeactivate
itsspanpowersupply,turningofftheHTU-RandHRE(ifpresent).Aslong
asthepatterncontinuestobesent,thespanpowersupplywillremain
disabled.Whenthepatternisnolongerbeingsent,theHTU-Cwill
reactivateitsspanpowersupply,turningtheremoteunit(s)on.Allunits
willretrainandreturntothedisarmedandunloopedstate.
Note: all codes listed above must be sent for a minimum of 5 seconds in order for them to be detected and acted upon.
* If NIU is enabled, then the HTU-R can be in network loopback when the HTU-C or HRE loopup codes are sent.