Black Box DESKTOP TELCO User manual

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 1 of 66
DESKTOP TELCO MODEMS
E1/G.703/V.35,36/X.21/V.24 NTU
MDS92xxx xDSL TRANSMISSION SYSTEMS
USER MANUAL
Version 2.5
Revision 30 Aug 2008
Document name MDS923AE-xxx-R2_MDS921AE-xx-R2-V2-3

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 2 of 66
© Copyright ©2008 by Black Box Network Services. The contents of this publication may not be
reproduced in any part or as a whole, transcribed, stored in a retrieval system, translated into
any language, or transmitted in any form or by any means, electronic, mechanical, magnetic,
optical, chemical, photocopying, manual, or otherwise, without the prior written permission of
Black Box Network Services. Published Black Box Network Services. All rights reserved.

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 3 of 66
VERSION CONTROL.................................................................................................................6
1SELECTION GUIDE ...........................................................................................................8
22 PANEL DESCRIPTION....................................................................................................8
3CONFIGURATION OPTIONS...........................................................................................10
3.1 XDSL..........................................................................................................................10
3.1.1 Master / Slave.......................................................................................................10
3.1.2 Normal / Dual pair / Multipoint mode .....................................................................10
3.1.3 Fixed rate / Adaptive setting..................................................................................10
3.2 E1-INTERFACE (2 MBIT/S G.703 /G.704)......................................................................11
3.2.1 Framing.................................................................................................................11
3.2.2 CRC4 Option.........................................................................................................11
3.2.3 E-bit Insertion........................................................................................................11
3.2.4 AIS Generation .....................................................................................................12
3.2.5 AIS Detection........................................................................................................12
3.2.6 Transmission of TS16...........................................................................................12
3.2.7 E1 synchronization modes....................................................................................12
3.3 NX64/RS232 INTERFACE (DCE)...................................................................................15
3.3.1 Nx64/RS232 Services...........................................................................................15
3.3.2 Nx64/RS232 Interface Types ................................................................................15
3.3.3 Nx64 Clock Directions (V.35, V.11 and V.28 only).................................................15
3.3.4 Nx64 Clock Modes (V.35, V.11 and V.28 only)......................................................15
3.3.5 Nx64 Block Diagram .............................................................................................16
3.3.6 Automatic V.54 loops............................................................................................17
3.4 TEST LOOPS................................................................................................................18
3.4.1 Standard Test Loops.............................................................................................18
3.4.2 Analog Loop Back.................................................................................................18
4PERFORMANCE MONITORING ......................................................................................19
4.1 G.826 PERFORMANCE MONITORING .............................................................................19
5ALARMS...........................................................................................................................20
5.1 GENERAL ....................................................................................................................20
5.2 LEDS..........................................................................................................................20
5.2.1 Status LEDs (except Multipoint Mode) ..................................................................20
5.2.2 Status LEDs Multipoint Mode................................................................................20
5.2.3 Local LED - Alarm Conditions ...............................................................................21
5.3 ALARM RELAYS NTU....................................................................................................21
5.3.1 Implementation .....................................................................................................21
5.3.2 Relay - Alarm Conditions.......................................................................................21
6NTU POWER CONCEPT..................................................................................................23
7MONITOR.........................................................................................................................24

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7.1 GENERAL ....................................................................................................................24
7.2 STRUCTURE &ORGANIZATION......................................................................................24
7.2.1 CLI Timeout ..........................................................................................................24
7.2.2 Password protection and access rights.................................................................25
7.2.3 Command set tree for Normal and Dual modes (* - Administrator access only) ....25
7.2.4 Command set tree for Multipoint mode (* - Administrator access only)..................26
7.2.5 Main Menu............................................................................................................26
7.2.6 Dual Channel SYNTAX.........................................................................................27
7.2.7 Common Commands............................................................................................27
7.2.8 Performance management PM..............................................................................28
7.2.9 Fault and maintenance management FMM...........................................................32
7.2.10 Configuration management CM.........................................................................39
7.2.11 Security management SM.................................................................................49
8SOFTWARE UPDATE......................................................................................................50
8.1 GENERAL ....................................................................................................................50
8.2 SOFTWARE DOWNLOAD................................................................................................50
9CONNECTORS' DESCRIPTION.......................................................................................54
9.1 XDSL CONNECTOR......................................................................................................54
9.2 E1 120 OHM CONNECTOR............................................................................................54
9.3 E1 75 OHM IN /OUT CONNECTORS...............................................................................54
9.4 NX64/RS232 DCE CONNECTOR ..................................................................................55
9.5 MONITOR INTERFACE ...................................................................................................56
9.6 POWER INTERFACE......................................................................................................56
10 TECHNICAL SPECIFICATION......................................................................................57
10.1 INTERFACES ................................................................................................................57
10.1.1 xDSL Line Interface...........................................................................................57
10.1.2 E1 Line Interface...............................................................................................57
10.1.3 V.35 DCE User Interface...................................................................................57
10.1.4 Monitor Interface...............................................................................................57
10.2 POWER SUPPLY...........................................................................................................57
10.3 ENVIRONMENTAL .........................................................................................................58
10.3.1 Climatic Conditions............................................................................................58
10.3.2 Safety / EMC.....................................................................................................58
10.4 PHYSICAL DIMENSIONS AND WEIGHT.............................................................................58
11 NX64 CABLES..............................................................................................................59
12 APPENDICES ...............................................................................................................64
12.1 INITIALIZATION ERRORS................................................................................................64
12.2 ABBREVIATIONS...........................................................................................................64
12.3 REFERENCES ..............................................................................................................66
12.3.1 Standards..........................................................................................................66

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FIGURES
Figure 2-1: Rear Panel...............................................................................................................9
Figure 2-2: Tabletop Front View.................................................................................................9
Figure 3-1: Synchronous Operation......................................................................................12
Figure 3-2: Synchronous Operation..........................................................................................13
Figure 3-3: Plesiochronous Operation......................................................................................13
Figure 3-4: Nx64 Block Diagram...............................................................................................16
Figure 3-5: standard Test Loops ..............................................................................................18
Figure 4-1: G.826 Performance Evaluation...............................................................................19
Figure 6-1: NTU Wetting current jumper locations ...................................................................23
Figure 7-1: Command Set Tree (Normal/Dual Pair Modes) ......................................................26
Figure 7-2: Command Set Tree Multipoint Mode......................................................................26

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Version: 2.5 Page 6 of 66
VERSION CONTROL
User Manual
Version
Date
Software
Version
Major changes to previous version
2.0
01.02.2006
3.0.V4.N.x
Initial Version
2.1
05.01.2007
3.0.V4.N.5
Modified unit Versions
2.2
21.03.2007
3.0.V4.N.5
Modified Chapter 3.2.6, 3.3.1, 7.2.9.9
Modified commands
2.3
30.07.2007
3.0.V4.N.7
Modified Chapter 7.2.9.24
Pinning Description E1 Connector
2 . 4
0 8 . 0 7 .
2 0 0 8
3 . 0 . V
4 . N . 7
M o d i f i e d C h a p t e r
7 . 2 . 9 . 2 4
M o d i f i e d c h a p t e r 8
2 . 5
2 3 . 0 9 .
2 0 0 8
3 . 0 . V
4 . N . 7
M o d i f i e d C h a p t e r 3 . 3 . 1
a n d 3 . 3 . 2
Warnings
INCORRECT USE OF THIS DEVICE, USE IN ANY OTHER ENVIRONMENT AND/OR
CHASSIS/HOUSING THAN PROVIDED BY BLACK BOX NETWORK SERVICES MIGHT LEAD TO
HARMFUL CONDITIONS. FAILURE TO FOLLOW THESE PRECAUTIONS MAY RESULT IN DEATH,
SEVERE INJURY OR PROPERTY DAMAGE.
BLACK BOX NETWORK SERVICES REFUSES TO TAKE ANY RESPONSIBILITY, FURTHERMORE,
NO WARRANTY IS GRANTED IN SUCH CASE!
Please read this manual carefully before operating the system.
Installation of this equipment has to be done by qualified personnel only.
EU Directive 2002/96/EC and EN50419
This equipment is marked with the above recycling symbol. It means that at the end of the life of
the equipment you must dispose of it separately at an appropriate collection point and not place
it in the normal domestic unsorted waste stream. (European Union only)

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Version: 2.5 Page 7 of 66

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 8 of 66
1 SELECTION GUIDE
2
2 wire (2,3Mb) 4 wire (2,3 Mb or 2x2,3Mb) E1 Nx64/RS232 Single Ethernet Port Multi-Service E1 - Nx64 - RS232 Point to Point Point to Multipoint FXS (only with optional board) FXO (only with optional board) Localy Powered - 48V-DC Remotely powerable Console Management
SNMP Management (through management module)
Telnet Management (through management module)
MDS921AE-E1-R2
MDS923AE-V35X21-R2
MDS923AE-V35X21-MP-R2
MDS923AE-E1-MP-R2
DESKTOP (TELCOLINK), E1, Nx64, V24, Ethernet Bridge

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 9 of 66
2 PANEL DESCRIPTION
Figure 2-1: Rear Panel
NE
FE
PWR
Figure 2-2: Tabletop Front View
N64/RS232 Sub-D25
female Connector
E1 120 Ohm Sub-D15
male Connector
Monitor Sub-D9
female Connector
Local/Remote
Power Switch
Optional
EarthTerminal
Power Mini-Fit
4 pin Connector
xDSL RJ-45
8 pin Connector
Tricolour
LED for
local
status
Tricolour
LED for
remote
status
Power
LED

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Version: 2.5 Page 10 of 66
3 CONFIGURATION OPTIONS
The following sections describe the various configuration options. The operating modes for the
NTU are configurable via the V.24 monitor interface on the rear panel as well as from remote
LTU (or NTU) via DSL in case of establishing of the link. The unit has to be configured for local
or remote power switch, placed on the rear panel.
3.1 xDSL
The following two configuration options refer to the xDSL side only and do not affect the E1 and
Nx64/RS232 interface operating mode.
3.1.1 Master / Slave
To start up an xDSL link, one system unit must be configured as master and the other one as
slave, as the link start-up procedure is controlled by the slave. If both system units are
configured as master or both as slave, no start-up will occur.
Normally, the LTU is configured as master (default setting). In addition, it is also possible to set
up an xDSL link with two NTUs, given that one is configured as master and the other one as
slave.
The "Master / Slave" option also affects the EOC related functions. Generally, the master-slave
rights are:
The master unit has local access as well as access to the slave unit. The master / slave,
G.992.1 Annex, Autorestart configuration and some other settings cannot be altered by the
master unit over the xDSL link for safety reasons (thus, default configuration cannot be
loaded remotely, see chapter 7 for details).
LTUs are always delivered as master (factory setting).
NTUs are always delivered as slave (factory setting).
The slave unit has the far end LED always off, whereas the master unit has it always on.
3.1.2 Normal / Dual pair / Multipoint mode
Units with two xDSL interfaces can operate in 2-wire (Normal) or 4-wire (Dual Pair) mode
according to ITU-T G.992.1. To start up an xDSL link, both system units must be set to the
same mode. Rate adaptation is not supported in Dual Pair Mode, so in this mode both system
units must be set to the same base rate.
In Multipoint mode E1 data is multiplexed to two xDSL interfaces. First n channel time slot is
transmitted through xDSL interface A, while other m channel slots –via xDSL interface B. There
are two sub-modes: PCM30, when TS16 is processed as signaling slot, and PCM31, when
TS16 is considered as channel slot. Multipoint mode is possible for Master only.
3.1.3 Fixed rate / Adaptive setting
In Normal and Multipoint modes Master can operate either in Fixed rate mode (the link will be
established according to Baserate setting if xDSL line conditions allow it) or in rate adaptation
mode (line rate will be selected automatically due to line conditions). In Normal mode Slave is
always in adaptive mode, thus link will be established according to Master settings.

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Rate adaptation is not supported in Dual Pair Mode, so in this mode both system units must be
set to the same base rate.
3.2 E1-Interface (2 Mbit/s G.703 / G.704)
The following configuration options refer to the E1 side only and do not affect the xDSL
operating mode.
3.2.1 Framing
3.2.1.1 Transparent Mode
In the transparent mode, the E1 data will be transmitted without any changes, whereas in the
framed mode the frame / multiframe alignment words and eventually the CRC4 bits are
searched for by the E1 framer.
The “CRC4” option is not relevant in the transparent mode.
Transparent mode is not supported in Multiservice and Multipoint modes.
3.2.1.2 Framed Mode ITU-T G.704
In the framed mode (framing according to ITU-T Rec. G.704), the incoming E1 data stream
passes through an E1 framer before entering the xDSL section. On the other side, the E1
data stream received from the xDSL section first passes through the E1 framer before being
transmitted to the E1 network.
The E1 framer operates in the CCS mode. Time slot 16 is fully transparent (except Multipoint
PCM30 mode).
Consider the “CRC4” option when operating in the framed mode.
3.2.2 CRC4 Option
If operating in the framed mode, the “CRC4” option can be used to adapt the LTU to specific E1
network requirements:
If enabled:
othe E1 framer will synchronize on CRC4 multiframes and CRC4 errors (detected
in the incoming stream) will be reported;
othe E1 framer regenerates the CRC4 multiframe alignment and checksum words
in the outgoing E1 signal. The A-Bit is set to 0 and the national bits (Sa-Bits) fully
transparent (except Multipoint mode).
If disabled, the E1 framer will synchronize on basic frames only and no CRC4 errors will be
reported. Time slot 0 is fully transparent, i.e. the A-Bit and all national bits (Sa-Bits) are fully
transparent (except Multipoint mode).
3.2.3 E-bit Insertion
If operating in the framed mode and “CRC4” option is enabled, the “EBIT” option can be used to
adapt the LTU to specific E1 network requirements:
If the automatic E-Bit generation is enabled, detected CRC4 errors will cause the assertion
of the E-bits.
If disabled, all the E-Bits are set to ‘1’.
The E-bit insertion option is not relevant in transparent mode or if “CRC4” is disabled.

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3.2.4 AIS Generation
If this option is enabled, an unframed AIS (all 1's) will be transmitted on the E1 side, irrespective
of whether the system is configured in the transparent or framed mode. AIS generation will be
activated on the following conditions:
xDSL link to the remote station is not established (loss of signal or loss of frame alignment
on xDSL side) or
remote station is sending AIS or
AIS-R alarm is active.
If “AIS Generation” is disabled, no signal will be transmitted on the E1 side if any of these three
conditions occurs.
3.2.5 AIS Detection
If “AIS Detection” is enabled, receiving AIS from the E1 side will cause the following actions:
The Non-Urgent alarm will be set active (AIS-S).
AIS will be transmitted to the remote station by AIS-R.
3.2.6 Transmission of TS16
In Normal and Dual Pair Modes E1 data is loaded to xDSL according ITU-T G.991.2. In these
modes TS0 of E1 is mapped to TS0 of xDSL, TS1 to TS1 and etc.
To activate the signaling over TS16 the unit has to be set to the PCM 30 mode. If the unit has
less TS than 16, the last TS is used for signaling if the PCM 30 mode is activated.
3.2.7 E1 synchronization modes
3.2.7.1 Clocking structure
Internal
Clock
Stuffing
Clock
recovery
xDSL
Tx
xDSL
Rx
E1
Tx
E1
Rx
2 Mbit transmit clock
xDSL recovered clock
E1-side xDSL side
Figure 3-1: Synchronous Operation
The primary TX clock source for module with E1 interface is:
For Master:
oE1 2 Mbit transmit clock or Internal clock (in case of E1 signal loss).
For Slave:
oE1 2 Mbit transmit clock (if plesiochronous mode is used (“PLL” option at slave
side is on)) or Internal clock (in case of E1 signal loss);

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Version: 2.5 Page 13 of 66
oxDSL recovered clock (if synchronous mode is used (“PLL” option at slave side is
off)).
The primary RX clock source for module with E1 interface is:
For Master:
oE1 2 Mbit transmit clock (if synchronous mode is used (“PLL” option at master
side is off)) or Internal clock (in case of E1 signal loss);
oxDSL recovered clock (if plesiochronous mode is used (“PLL” option at master
side is on)) or Internal clock (in case of xDSL signal loss).
For Slave:
oxDSL recovered clock or Internal clock (in case of xDSL signal loss).
The clock sources are automatically switched by the microcontroller, depending on the actual
signal and clock status, which is updated every 100 ms.
3.2.7.2 Synchronous and plesiochronous operation
Both synchronous and plesiochronous operation modes are possible.
Synchronous operation occurs, when the E1 equipment at one end of the xDSL link uses the
receive clock as transmit clock, as shown below. In this case “PLL” option must be switched off
on both master and slave sides.
E1 NTU /
LTU
Tx
Rx
2048 kHz Clock
E1 Equipment
xDSL Channel
Tx
Rx
E1 Equipment
E1 NTU /
LTU
Master
Slave
Figure 3-2: Synchronous Operation
Plesiochronous operation occurs, when the E1 equipment at both ends of the xDSL link has its
own clock generator, as shown below. In this case “PLL” option must be switched on both
master and slave sides.
E1 NTU /
LTU
Tx
Rx
2048 kHz Clock
E1 Equipment
xDSL Channel
Tx
Rx
E1 Equipment
E1 NTU /
LTU
Master
Slave
2048 kHz Clock
Figure 3-3: Plesiochronous Operation
Warning:
Do not configure the E1 interfaces at both ends to use the receive clock as

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Version: 2.5 Page 14 of 66
transmit clock except if one xDSL equipment is an LTU using the "External
Clock" option. Otherwise there will be no defined clock.
N o t e :
O r i o n 1 r e p e a t e r s s u p p o r t o n l y
s y n c h r o n o u s o p e r a t i o n . T o i n c r e a s e
s y s t e m
p e r f o r m a n c e u s e s y n c h r o n o u s m o d e
f o r m a s t e r a n d s l a v e i f r e p a t e r s a r e
u s e d .

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3.3 Nx64/RS232 Interface (DCE)
The following configuration options refer to the Nx64/RS232 (V.35/V.11/V.28/RS232 –SW
configurable) side only and do not affect the xDSL operating mode.
3.3.1 Nx64/RS232 Services
One can choose between three available services:
E1 only: With this service mode, the Nx64 interface is shut down. No payload data is
transferred to/from Nx64 transceiver.
Nx64 only: With this service mode, the E1 transceiver is shut down or is sending AIS. No
payload data is transferred to/from E1 transceiver.
Multiservice Nx64 & fE1: With this service mode, the available xDSL payload is divided into
Nx64 (or RS232) payload and E1 payload. The Nx64 payload always starts at timeslot 1
upwards, skipping timeslot 16 up to timeslot 31, and then using timeslot 16 and at last
timeslot 0. The E1 payload follows after the last used Nx64 timeslot. The RS232 payload
starts at timeslot that is defined by “RS232SLOT” command. For data rates from 110 to
38400 bps RS232 payload occupies one timeslot. For data rates 57600 and 115200 bps
RS232 payload occupies 2 and 3 timeslots accordingly.
3.3.2 Nx64/RS232 Interface Types
The following interface types/data rates are supported (SW configurable):
V.35 / 64…2048 kbps;
V.11 (V.36 or X.21, cable selectable) without termination / 64…2048 kbps;
V.11 (V.36 or X.21, cable selectable) with termination / 64…2048 kbps;
V.28 (synchronous) / 64 and128 kbps;
RS232 (asynchronous) / 110, 150, 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600
and 115200 bps.
3.3.3 Nx64 Clock Directions (V.35, V.11 and V.28 only)
There are two options available:
codirectional: Transmit clock and transmit data have same directions, i.e. both are inputs to
the modem at signal number 113 (clock) and 103 (data).
contradirectional: Transmit clock and transmit data have opposite directions, i.e. transmit
clock is output from modem at signal number 114 and transmit data is input to the modem at
signal number 103.
3.3.4 Nx64 Clock Modes (V.35, V.11 and V.28 only)
The following table shows different combinations of clock modes, some of which are invalid.
There are three possible DCE clock modes:
from E1: This clock mode is active when the E1 interface is active.
external: In this clock mode, the DCE is clock slave and has its PLL on the transmit side
(from Nx64 to the xDSL interface) is on.
internal: In this clock mode, the DCE is clock master and the PLL is off, generating a
2048 kHz clock from the internal oscillator directly.

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Service
DTE
Clock Mode
DCE
Clock Mode
DCE
Clock Direction
xDSL
Clock Mode
Nx64 only
Slave
internal
don’t care
Master
Slave
external
don’t care
Slave
Master
external
codirectional
Slave
Master don’t care
external
contradirectional
Master don’t care
Master
don’t care
don’t care
Master
Nx64 & fE1
Slave
from E1
don’t care
Master
Slave
from E1
don’t care
Slave
Master
don’t care
don’t care
don’t care
Note: Invalid clock modes are ruled out.
3.3.5 Nx64 Block Diagram
The following block diagram shows the receive and transmit path separately. Each direction
possesses a FIFO buffer and a PLL.
Figure 3-4: Nx64 Block Diagram
Rx
FIFO
Rx Framer
RxClk_xDSL
RxData_xDSL
Rx PLL Osc.
FIFO Enable
RxClk_Nx64
RxData_Nx64
RxSync_xDSL
Tx
FIFO
Tx Framer
TxClk_xDSL
TxData_xDSL
Tx PLLOsc.
FIFO Enable
TxClk_Nx64
TxData_Nx64
TxSync_xDSL
TxClk_E1
TxSync_E1
TxData_E1
Service

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3.3.6 Automatic V.54 loops
System supports V.54 loops, managed by 140-142 lines. Supporting of V.54 loops is SW
programmable.
Tx
TxRx
Rx
Loop 1 Loop 1Loop 2
xDSL
Slave Master
Master
Slave
State Name
RL
LL
TI
RL
LL
TI
DSR
State Description
Normal
1
1
1
1
1
1
0
Data Transmission
Loop1 at Master Side
(Setting by terminal
command)
1
1
0
1
1
1
0
TX Data is looped back to RX
at Nx64 Master Network
Interface. LOOP1 alarm is
active on Master side.
Loop2 (Setting by
terminal command)
1
1
0
1
1
0
1
Data from DSL is looped
back towards Master side in
Slave DSP (Core loopback).
LOOP2 alarm is active on
Master and Slave sides.
Loop1 at Slave Side
(Setting by terminal
command)
1
1
1
1
1
0
0
TX Data is looped back to RX
at Nx64 Slave Network
Interface. LOOP1 alarm is
active on Slave side.
Automatic Loop1
setting at Master side
(activated by LL line
on Master interface)
1
0
0
1
1
1
0
TX Data is looped back to RX
at Nx64 Master Network
Interface. LOOP1 alarm is
active on Master side
Automatic Loop2
(activated by RL line
on Master interface)
0
1
0
1
1
0
1
Data from DSL is looped
back towards Master side in
Slave DSP (Core loopback).
LOOP2 alarm is active on
Master and Slave sides.
Automatic Loop1
setting at Slave side
(activated by LL line
on Slave interface)
1
1
1
1
0
0
0
TX Data is looped back to RX
at Nx64 Slave Network
Interface. LOOP1 alarm is
active on Slave side.

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3.4 Test Loops
3.4.1 Standard Test Loops
The test loops can be activated via the monitor interface.
Figure 3-5: standard Test Loops
Note:
On the slave side, Loop 1 can be activated locally, Loop 2 can be activated locally or remotely
by the master (LOOP2R command). Loop 1 and Loop 2 on slave can be activated from master
via virtual terminal connection (see CONNECT command description).
Both the NE LED on the slave and the FE LED on the master will be lit amber when Loop2 is
active on slave unit.
At the regenerator point Loop2 on N-side can be activated locally or remotely by the master
(LOOP2R command). Loop 2 on C-side and Loop1 can be activated locally or remotely by the
master via virtual terminal connection (see CONNECT command description and Repeater
Manual).
Both the NE LED on the regenerator and the FE LED on the master will be lit amber when
Loop2 is active.
On the master side, Loop 1 and Loop2 can only be activated locally. The NE LED will be lit
amber when Loop 1 or 2 is active.
3.4.2 Analog Loop Back
To test the Black Box Network Services equipment itself, the Analog Loop Back can be used.
To perform this test, the xDSL - cable has to be disconnected from the unit and the test can be
activated with the appropriate monitor command (see chapter 'Black Box Network Services
Monitor').
During the Analog Test Loop, the xDSL-receiver part receives the transmitted signal of its own
transmitter due to the impedance mismatch in the xDSL-line transformer.
All data of the user interface is looped back according to the UIF and its settings.
An Analog Loop Back causes a non-urgent alarm.
Master
Slave
N-side xDSL
Channel
Loop 1 Loop 2
Loop 2 Loop 1
TX
TX
RX
RX
Repeater
Loop 2 N
C-side xDSL
Channel
Loop 1
E1 interface
Loop 2 C

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4 PERFORMANCE MONITORING
The transmission performance of an xDSL link can be monitored in two different ways. The
xDSL signal quality is typically used during installation and maintenance procedures, whereas
the G.826 error performance parameters are intended to be used for long-term evaluation of
operating xDSL links. Refer also to the “SQ” and “G826” monitor commands described in the
“Black Box Network Services Monitor” section.
4.1 G.826 Performance Monitoring
The G.826 error performance parameters provide quantitative performance information of a
specific loop. They are intended to be used for long-term evaluation of operating xDSL links.
The evaluation of the G.826 error performance parameters is based on CRC (Cyclic
Redundancy Check) error detection:
Slave
CRC4
CRC6
TX
RX
E1
Test
Gen.
CRC4/E-bit
G.826
Evaluation
Gen.
Test
CRC6/FEBE
xDSL
Channel
Master
CRC6
CRC4
Test
Gen.
CRC4/E-bit
G.826
Evaluation
Gen.
Test
CRC6/FEBE
TX
RX
E1
Figure 4-1: G.826 Performance Evaluation
CRC generation and detection on the LTU/NTU are handled separately for the E1 side and the
xDSL side, while on the ADD-DROP Repeater CRC generation and detection are handled
separately for the E1 side and both xDSL sides.
On the E1 side, four CRC4 check bits are generated per sub-multiframe (SMF) and compared
with the corresponding CRC4 bits in the following SMF. If they do not match, the CRC4 error
counter is incremented. The opposite station is informed of detected CRC4 errors by setting E-
bits in the transmitted frames. At the same time, the E-Bits from the opposite station are
counted and can be used for performance monitoring.
Similarly, on the xDSL side, six CRC6 check bits are generated per xDSL frame for each
channel and direction. For signaling detected block-errors in the return direction, the FEBE-bits
are used. The HDSL G.826 performance of the opposite unit is calculated according to these
FEBE-bits.
CRC6 errors are used by software to count the block-errors of the respective xDSL channel and
to evaluate its error performance according to ITU-T Rec. G.826.
For the E1 interface, calculations according to G.826 are only possible in the framed mode with
CRC4 option enabled. In framed mode with CRC4 option disabled only FAS-errors are
detected.
The estimation of a bit-error rate is not within the scope of the G.826 calculations.

TELCOLINK DT - AccessDSL NTU User Manual
Version: 2.5 Page 20 of 66
5 ALARMS
5.1 General
This chapter describes a possible implementation for the alarm signalization.
5.2 LEDs
The two NTU LEDs 'far end (FE) status' and 'near end (NE) status' are used to display normal
operation condition and alarm condition. Each LED can be green, amber or red when lit
according to the following table. The third LED is used for power representation.
NE LED is responsible for local status of N-side and E1 interfaces, while FE LED is responsible
for local status of C-side interface.
5.2.1 Status LEDs (except Multipoint Mode)
Status
Local (NE) LED
Remote (FE) LED
LTU Power failure
Off
off
Hardware - / Software failure
Blinking Red
off
No EOC connection established
On
red
Normal operation local
Green
don’t care
Normal operation remote
Don’t care
green
xDSL framer synchronizing
Blinking Green/Amber
don’t care
xDSL training
Blinking Amber
don’t care
Minor alarm local
Amber
don’t care
Minor alarm remote
Don’t care
amber
Major alarm local
Red
don’t care
Major alarm remote
Don’t care
red
5.2.2 Status LEDs Multipoint Mode
Status
Local (NE) LED
Remote (FE) LED
Power failure
Off
off
Hardware - / Software failure
Blinking Red
off
No EOC connection established
On
red
Normal operation local
Green
don’t care
Normal operation remote
Don’t care
green
Minor alarm local or one channel
major alarm local
Amber
don’t care
Minor alarm remote or one
channel major alarm remote
Don’t care
amber
Both channel major alarm local
Red
don’t care
Both channel major alarm remote
Don’t care
red