User Guide AM768A AM2048A MP AM2048A CAP

User Guide AM768A AM2048A MP AM2048A CAP
User Guide
AM768A
AM2048A MP
AM2048A CAP
AM2048A OS/M
Ascom Telecom Part Number :
1/187/500/610
Issue 8 - Dec 2001.
ascom telecom
USER GUIDE
AM768A/AM2048A
THE INFORMATION CONTAINED IN
THIS DOCUMENT IS CONFIDENTIAL TO
ascom TELECOMMUNICATIONS LTD.
AND MAY
NOT BE DISCLOSED OR REPRODUCED IN WHOLE
OR PART WITHOUT THEIR WRITTEN CONSENT.
©
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Note:
USER GUIDE
AM768A/AM2048A
The information contained in this document is supplied without liability for errors or
omissions.
Ascom Telecommunications Limited reserves the right to make changes to this
document at any time without notice.
Compliance Notes and Safety Instructions:
Caution – Hazardous voltage inside the equipment
Safety Instructions:
This apparatus must be installed and maintained by SERVICE PERSONNEL.
Disconnect the mains plug and the NTP line connection before attempting to change
the user interface plug-in module.
The mains plug on the equipment serves as the disconnect device, therefore a socket
outlet shall be installed near the equipment and shall be easily accessible.
Power Rating Information – AC plug top adapter:
Voltage Range 240V – 10% +6%
Current Range 25mA to 50mA
Frequency Range
50/60Hz
Power Rating Information – 240V AC in-line adapter:
Voltage Range 240V – 10% +6%
Current Range 25mA to 50mA
Frequency Range
50/60Hz
Power Rating Information – 110V AC in-line adapter:
Voltage Range 110V – 10% +6%
Current Range 50mA to 100mA
Frequency Range
50/60Hz
Power Rating Information – DC Source:
Voltage Range 40.5V to 58V
Current Range 70mA to 200mA
TTE – Network Statement
Safety Statements
The copper DSL line connection has a safety status of TNV-3
The Plug Top DC Power connection has a safety status of TNV-2
The X.21 Digital Network Interface Port has a safety status of SELV
The V.35 Digital Network Interface Port has a safety status of SELV
The 10/100 BaseT Port has a safety status of SELV.
For the G.703 Port Connection to Unexposed Environments:
The Alarm Port has a safety status of SELV.
The G.703 Digital Network Interface Port has a safety status of SELV
For the G.703 Port Connection to Exposed Environments:
The Alarm Port has a safety status of earthed SELV.
The G.703 Digital Network Interface Port has a safety status of TNV-1
The Protective Earth on the rear panel MUST be connected (see Section 4 on
Installation)
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Definitions:
Exposed Environment
A TELECOMMUNICATIONS NETWORK is considered to be an exposed
environment if one or more conditions for an unexposed environment are not fulfilled.
Unexposed Environment
A TELECOMMUNICATIONS NETWORK is considered to be an unexposed
environment if the following conditions apply to all parts of the network
a) The possible effect of indirect lightning has been reduced by measures described
in IEC 61312-1.
b) The possibility of having different earth potentials has been reduced by
connecting all equipment within the network to the same equipotential bonding
system (see HD 384).
c) The possibility of power cross/contact has been reduced (see HD 384).
d) The possibility of induced transients and voltages has been reduced.
Caution – Laser Product
The Optical Interface is classified as a CLASS 1 LASER PRODUCT.
Caution – Electrostatic sensitive device
Electro-static discharge (ESD) Warning:
Antistatic precautions should be observed at all times.
If the unit is power fed from the DSL line interface then a functional earth MUST be
connected. (See Section 4 on Installation)
EMC Statement
This is a Class A product. In a domestic environment this product may cause
radio interference in which case the user may be required to take adequate
measures.
Manufacturers Declaration*
Ascom Telecommunications Limited declares that this product is in conformity with the
essential requirements of the ‘R&TTE directive 1999/5/EC’.
* A copy of the Declaration of Conformity is available upon request from Ascom Telecommunications Ltd.
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Contents
COMPLIANCE NOTES AND SAFETY INSTRUCTIONS: ................................... 3
1.
INTRODUCTION ........................................................................................................................................ 7
2.
CONSTRUCTIONAL DETAILS................................................................................................................ 8
3.
SYSTEM OVERVIEW .............................................................................................................................. 10
3.1
3.2
3.3
3.4
3.5
3.6
4.
COPPER TRANSMISSION ......................................................................................................................... 10
OPTICAL TRANSMISSION ....................................................................................................................... 11
DSL TRANSMISSION FRAME ................................................................................................................. 12
CONTROL CIRCUIT................................................................................................................................. 12
ALARM INTERFACE ............................................................................................................................... 13
USER INTERFACE MODULES .................................................................................................................. 13
INSTALLATION ......................................................................................................................................... 14
4.1
CONNECTION OF PROTECTIVE EARTH.................................................................................................... 14
4.2
POWER ON SEQUENCE ........................................................................................................................... 14
4.3
LOGGING ON ......................................................................................................................................... 14
4.4
SETTING MASTER/SLAVE MODE. ........................................................................................................... 15
4.5
SETTING THE USER INTERFACE ............................................................................................................. 15
4.6
SETTING THE NX64K USER DATA RATE ............................................................................................... 16
4.7
SELECTING THE CIRCUIT CONFIGURATION ............................................................................................ 16
4.7.1
Point to Point Link........................................................................................................................ 17
4.7.2
Point to Multipoint Link................................................................................................................ 20
4.8
BRINGING INTO SERVICE ....................................................................................................................... 22
4.9
TRANSMISSION PARAMETERS ................................................................................................................ 23
4.9.1
Transmission Range...................................................................................................................... 23
4.9.2
End to End Delay.......................................................................................................................... 24
4.9.3
Jitter.............................................................................................................................................. 24
4.10 G.703 INTERFACE OPTIONS ................................................................................................................... 25
4.10.1 Unstructured Operation................................................................................................................ 25
4.10.2 Structured Operation .................................................................................................................... 26
4.10.3 Structured Working, CRCs Enabled ............................................................................................. 27
4.10.4 ETS 300 233 Loopbacks ............................................................................................................... 28
5.
PHYSICAL INTERFACES ....................................................................................................................... 30
5.1
MAINS POWER SUPPLY .......................................................................................................................... 30
5.1.1
240V Plug Top PSU...................................................................................................................... 30
5.1.2
240V In Line PSU ......................................................................................................................... 30
5.1.3
110V In-line PSU.......................................................................................................................... 30
5.2
DC POWER INLET .................................................................................................................................. 30
5.3
COPPER TRANSMISSION LINE ................................................................................................................ 31
5.4
OPTICAL TRANSMISSION LINE ............................................................................................................... 31
5.5
SERIAL CONTROL .................................................................................................................................. 31
5.6
ALARM INPUT/OUTPUT PORT ................................................................................................................ 32
5.7
INTERFACE MODULES ........................................................................................................................... 33
5.7.1
G.703 ............................................................................................................................................ 33
5.7.2
X.21............................................................................................................................................... 34
5.7.3
V.35............................................................................................................................................... 35
5.8
FRONT PANEL ........................................................................................................................................ 36
5.8.1
Controls ........................................................................................................................................ 36
5.8.2
Indicators...................................................................................................................................... 37
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6.
AM768A/AM2048A
INTERNAL LINKS AND FUSES .................................................................................. 38
6.1
6.2
6.3
6.4
6.5
7.
USER GUIDE
G.703 PLUG IN MODULE ....................................................................................................................... 38
X.21 PLUG IN MODULE MK I................................................................................................................ 38
X.21 PLUG IN MODULE MK II .............................................................................................................. 39
V.35 PLUG IN MODULE (MK I AND MK II)........................................................................................... 39
MOTHERBOARD ..................................................................................................................................... 40
COMPLIANCE NOTES .............................................................................................................................. 41
7.1
TELECOMMUNICATION STANDARDS ...................................................................................................... 41
8.
GLOSSARY ................................................................................................................................................ 42
9.
TROUBLESHOOTING ............................................................................................................................. 44
APPENDIX A - X.21/V.35 CABLE LENGTHS............................................................................................... 45
X.21 CABLES - POTENTIAL PROBLEM LENGTHS ............................................................................................... 46
V.35 CABLES - POTENTIAL PROBLEM LENGTHS ............................................................................................... 48
APPENDIX B – ORDERING INFORMATION ............................................................................................. 50
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1. Introduction
This manual applies to the High Speed DSL Systems, designed and manufactured by Ascom
Telecommunications Ltd in the U.K..
The modems provide synchronous communications at user data rates between 64kbps and 2048kbps
over up to three twisted pair cables or a single optical fibre. The equipment has modular transmission
and user interfaces, which allows the equipment to be configured to meet many different installation
requirements. Both rack and desktop versions of all units are available. Desktop units are AM2048A…
and rackmount units are AM2048B… This manual covers the desktop units.
The AM2048A OS provides full duplex transmission at 2.048Mbps over a single single-mode optical
fibre.
The AM2048A OM provides full duplex transmission at 2.048Mbps over a single multi-mode optical
fibre.
The AM2048A MP provides full duplex transmission at 2.048Mbps using 3 copper pairs. It can be
used in point to point or point to multipoint mode. The line code is 3B1O.
The AM2048A CAP provides full duplex transmission at 2.048Mbps using 1 or 2 copper pairs. It can
be used in point to point or point to multipoint mode. The line code is CAP.
The AM768A is a reduced cost unit, available with a single transmission module. This has most of the
functionality of the AM2048 but reduced payload bandwidth due to using one transmission line
instead of three. It is intended mainly for use in point to multipoint mode in conjunction with the
AM2048A MP or the AM2048B MP
Separate interface modules can also be purchased in order to modify the units for operation with a
different terminal interface at a later date.
Throughout the handbook, all types of unit are referred to as DSLU (Digital Subscriber Line Unit)
The DSLU can easily be configured via a dumb terminal. It is recommended to use a VT100 terminal
emulation program running on a notebook or palmtop PC. Using the menu system with on-line help
should reduce the need to refer to the handbook.
Once configured, the operation of the DSLU is totally automatic. In the event of line disturbances or
power failure, the data link is restored without operator intervention.
Chapter 4 (Installation) describes the basic set up procedure and this should be read prior to setting
up any link.
The VT100 Management User Guide gives a full description of the menu system..
Modifications to line cords and power supply leads are available for country specific requirements. In
such cases, the line cord pinout may be different. The basic model is the same, line cords and power
cords are separate plug in items.
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2. Constructional Details
Figure 1 Desktop Unit
The desktop unit is housed in a grey non-flammable plastic case (UL94 rating V0). The membrane
front panel contains 5 LED indicators and 3 push button switches with LEDs to indicate their
activation.
LEDs
• Urgent Alarm
• Non Urgent Alarm
• Test
• Power
• Master
Buttons
• Local Loop
• Loop Back
• Rem Loop
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On the rear panel there are the following connectors:
–48V DC supply inlet socket
3-pin mini-fit
line interface
8 way RJ45 (Copper)
FC/SPC (Optical) See Appendix B for other options.
Management port interface
9 way female D-type
Alarm interface
13 way circular DIN
Data Ports (depending on module fitted)
G.703 120Ω
8 way RJ45
G.703 75Ω
BNC
X.21
15 way D-type female
V35
34 way MRAC female
The data interface connector type will be from one of the three user specified interfaces available.
They are detailed in section 5. The plastic housing contains the main PCB. The plastic case has an
internal metallised layer for EMC screening purposes. The membrane front panel is attached to the
main PCB with a flexible circuit connector.
Also included is a 3 metre screened, stranded, Category 5 line cord terminated in 8-way RJ45 plugs
at both ends.
Optional plug-top and in-line mains adapters are available with a 1.8 metre long DC lead, terminating
in a 3-pin mini-fit plug. Also available is a VT100 Management connection cable.
The overall dimensions of the unit are 274mm(L) x 251mm(W) x 55mm(H).
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3. System Overview
Transmission Modules
Transceiver
Analogue
Interface
Pair 1
Transceiver
Analogue
Interface
Pair 2
DSP
Chip
Transceiver
Analogue
Interface
Pair 3
DSP
Chip
DSP
Chip
User Interface Module
G703
75/120
ohms
Primary Rate
Interface
ascom
HDSL
Interface
Chip
Micro
Controller
Figure 2 Copper System Block Diagram
3.1 Copper Transmission
The copper system is intended for operation on 2-wire local telephone network circuits, such as those
meeting BT EPS-9 (Note: the DSLU requires between one and three such circuits). It will operate
satisfactorily on unloaded lines having a wide range of characteristics; bridge taps can be tolerated,
dependent upon their characteristics. Although, the system requires a baseband circuit, a continuous
loop at DC is not required. The system can transmit data at rates between 64k and 2048k.
For the copper system, echo cancellation is used to eliminate the unwanted reflections of the
transmitted signal from the receiver input.
The line is connected to the transmission circuit via a line transformer, which acts as a balun and
provides isolation; there is surge protection across the transformer line connections. The transmission
circuit utilises a custom IC and a number of proprietary components to perform the signal processing
described above.
When more than one transmission line is in operation, each transmission system operates with the
same bit rate derived from an oscillator in the master unit.
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Optical Transmission Module
Laser
Driver
User Interface Module
G703
75/120
ohms
Primary Rate
Interface
ascom
HDSL
Interface
Chip
ascom
Tranceiver
Codec
Chip
Clock
Recovery
Optical
Duplexer
Analogue Rx
and
Channel
Separation
Filter
Micro
Controller
Figure 3 Optical System Block Diagram
3.2 Optical Transmission
The optical transmission interface module fits into the same envelope as three copper modules and is
designed to operate over a single optical fibre. This is accomplished using an optical duplexer, which
integrates a laser and a photodiode in a single package. Both directions are transmitted at the
1310nm optical window, leaving the 1550nm window free. The interface module encodes the DSL
framed data using a 5B6B block code for error monitoring and spectral shaping.
Sub-carrier modulation is used to increase the separation between the upstream and downstream
directions. Baseband transmission is used from ELU to NTU, whereas the other direction is
modulated onto a carrier.
For transmission over single-mode fibre, order the AM2048 OS.
For transmission over multi-mode fibre, order the AM2048 OM.
The AM2048A OS and AM2048 OM are Class I products in accordance with EN60825-1 and
therefore inherently safe.
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3.3 DSL Transmission Frame
Both of the above transmission systems operate in a bit pump mode. The DSL frame is sent over this
‘data pipe’. The DSL frame contains the following
• Sync word
• Stuff bits
• Stuff control bits
• EOC channel
• Customer data
The nominal DSL frame is always 6ms long, regardless of the transmission rate of the individual
channels.
The DSL frame length is adjusted slightly by the use of stuff bits. There may be 4 stuff bits or 2 stuff
bits per frame. The stuff bits are used to adjust the effective payload bandwidth of the DSL frame.
If the user rate clock is slightly quicker than the line rate clock then less stuff bits are sent.
Alternatively, if the user rate clock is slightly slower than the line rate clock then more stuff bits are
sent. This mechanism allows the line rate bandwidth to be adjusted to match the user rate bandwidth.
At the receive end, the rate at which the stuff bits arrive is used to recover the user clock.
The transmit and receive paths may be operated independently from one another so that when a
G.703 user interface is present, the transmit and receive clocks are allowed to vary independently by
+50ppm. (Note. When operating with X.21 or V.35 interfaces, there is only a single clock at each user
interface.)
The Embedded Operation Channel (EOC) is carried in spare overhead bits in the transmission frame.
Packetised SNMP SET and GET messages are passed over the link from the ELU to the NTU, which
answers with the appropriate SNMP response.
Byte timing is maintained by the transmission system and is available if required.
3.4 Control Circuit
The control circuit is based on a micro-controller and determines the operational status of the unit
according to the state of the transmission system, the data interface and the configuration information
received from the terminal.
Configuration data and two copies of the application are stored internally in FLASH memory. On
power-up the application program is copied from FLASH to RAM from where it is executed. The main
application program is backed up so that if a corruption occurs it can be corrected. This also enables
the programming of a new application while the equipment is operating normally. Control is
transferred to the new application after an automatic restart at the end of the download. This
minimises the interruption of payload traffic. Also, if programming is interrupted, the previous version
of software will remain intact. A new application program may also be downloaded from the ELU to
the remote NTU over the line.
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3.5 Alarm Interface
A 13 pin circular DIN connector provides access to 6 alarm inputs that are used to detect metallic
contact closure. For example, they can be used to sense a cabinet door open or temperature sensors.
The priority of these auxiliary alarms may be programmed through the “Alarms>Severity Level
Settings” screen.
There are also relay contact outputs to indicate urgent and non-urgent alarms. This allows the system
to be easily integrated into the alarm systems of other equipment.
3.6 User Interface Modules
The user interface is provided by a plug-in module of which there are six types:
•
•
•
•
•
•
G.703, with software selectable 75ohm or 120ohm ports
X.21
V.35
G.703 MK II (with 1 + 1 protection switch)
X.21 MK II (with tail buffer)
V.35 MK II (with tail buffer)
The existing interface module can be changed out using a pluggable replacement unit. These can be
ordered separately using the part numbers detailed below. For part numbers and order codes see
Appendix B.
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4. Installation
This chapter describes the basic steps that are required to set up a system involving the DSL Modem.
4.1 Connection of Protective Earth
If it is required to connect the G.703 port to a circuit that is defined as TNV, then a protective earth
must be connected to the earth bond stud on the rear panel. See the Compliance Notes and Safety
Instructions inside the front cover.
If the unit is power fed then a functional earth must be connected to the earth bond stud on the rear
panel to provide a discharge path to ground for ESD protection. See the Compliance Notes and
Safety Instructions inside the front cover.
4.2 Power On Sequence
With no DTE or line connected to the DSLU on power up, the following LED sequence will be
displayed:
1
2
3
4
5
6
7
8
9
10
Urgent
Non-Urgent
Test
Power
Prior to the sequence starting, a random pattern may appear momentarily.
During sequence 1 to 7 the LEDs are illuminated in turn as an LED confidence test.
During stage 8 the test LED flashes as the internal self-test sequence is completed. The flashing will
normally last for about 4 seconds, however, if a new application has been loaded this time will be
extended by about 10 seconds while a backup copy of the application is made.
With no external connections the unit will sense the loss of external signals, raise the urgent alarm
and stop at stage 9.
When the system has been installed and is working correctly, the unit should move to stage 10.
4.3 Logging On
Connect a VT100 terminal (or PC running a VT100 emulation program) to the 9-way serial port on the
rear of the unit. The log on screen should appear automatically once the DSLU detects the terminal.
Type ‘C’ to select Configuration, then press ‘Enter’
Type ‘ascom’ the default password setting, then press ‘Enter’
The top level menu system displays the sub-menus available.
For a full description of the menu system, refer to the ‘VT100 Management User Guide’.
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4.4 Setting Master/Slave mode.
For all modes of operation, one unit must be set to master mode, while the other unit is set to slave
mode. The master unit is referred to as the ELU or Exchange Line Unit and the slave unit is referred
to as the NTU or Network Terminating Unit. The front panel ‘Master’ LED indicates the mode of the
unit.
The ELU is a ‘master’ in several senses. The master end provides the source of the bit rate timing for
the transmission line(s). The ELU is also the ‘master’ from a network management point of view. It
contains the database of configuration information for itself and all connected NTUs. The alarm and
performance monitoring history is saved at the ELU. When the management terminal is connected to
the ELU it can read all of the information from the remote NTU, whereas when the management
terminal is connected to the NTU, only the local information is obtainable.
The factory default is for the unit to be configured as a slave (NTU).
To change the setting, using the terminal go to the “Configuration>Master/Slave” screen and select
the appropriate option. (use the arrow keys or tab key to navigate and the spacebar to change the
setting). The basic setup for all modes is as follows:
At the master end:
Configuration>Master/Slave
1. select Master.
2. select Point- to Point or Point to Multipoint, as appropriate.
3. enable the required number of lines
At the slave end:
The factory default setting should allow the units to get into sync, otherwise:
Configuration>Master/Slave
4. select Slave.
5. select Point- to Point or Point to Multipoint, as appropriate.
6. enable the required number of lines
The unit will automatically reboot with the new settings once the “return” key is pressed to accept the
changes. You will then be invited to log back on to the system.
It is possible to set Master/Slave by using the front panel buttons if a terminal is unavailable, see
section 5.8.1.
4.5 Setting the User Interface
The unit automatically detects what kind of user interface is plugged in and displays the appropriate
screen in the “Configuration>User Port” screen.
For X.21 and V.35, DTE/DCE selection is carried out by moving the link header on the user interface
plug-in module. The software automatically senses the link setting and sets the unit up accordingly.
To check the user interface and any link settings, using the terminal, go to the “Information>System”
screen, this will display which user interface has been plugged in, and which mode it is in.
Once a unit is configured as an ELU, the expected interface at the NTU may be set, or by default, the
unit will auto-discover the NTU user port configuration after the line gets into synchronisation.
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4.6 Setting the Nx64K User Data Rate
For X.21 and V.35 the data rate may be set in increments of 64kbps. The default setting of N = 6. The
data rate is set by entering the desired value of N. The full range of N is from 1 to 32. The screen
display gives the equivalent data rate in kbps for the value of N. The software automatically restricts
the value of N to match the user interface and line interface combination. e.g. for an Am768, the
maximum value of N = 12.
For a G.703 to Nx64 configuration, the maximum value of N is 31 as only timeslots 1 to 31 are
transported over the transmission link. N may be further restricted depending on the transmission
system.
For software up to version 2.9, the value of N must be entered for each end of the link as follows:
At the master end:
Configuration>User Port
1. Set the desired value of N.
2. Press F8, to select the remote end
3. Set the desired value of N
4. Press Enter to activate the change.
For software versions greater than 2.9, the value of N only needs to be set once:
At the master end:
Configuration>User Port
1. Set the desired value of N.
2. Press Enter to activate the change.
4.7 Selecting the Circuit Configuration
The term ‘digital section’ refers to the data link between the user ports of the connected DSLUs.
In a standalone section, the DSLUs provide the complete transmission system.
In a tandem section, the DSLUs are used to extend an existing circuit or network port. To achieve
synchronous data transfer, the master DSLU must derive its timing from the circuit to which it is
connected.
A Point to Point link requires two DSLUs, one master and one slave.
A Point to Multipoint link can have up to four DSLUs, one master and up to three slaves.
The DSLU at one end of the digital section is selected to be a Master (ELU), the remote end(s) are
selected to be slave(s) (NTUs).
For a tandem section, the DSLU connected to the tandem section is configured as the master.
Please refer to the diagrams on the following pages.
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4.7.1 Point to Point Link
4.7.1.1 Standalone Section
ELU
NTU
Terminal 1
Terminal 2
The transmission channel can be a single optical fibre, one, two or three copper pairs.
4.7.1.1.1 G.703 to G.703 Internal Timing
Slave terminals are connected to the digital section at both ends, a clock inside the ELU then
becomes the reference clock for the entire system.
T
T
T
ELU
T
NTU
T
Terminal 1
Terminal 2
The internal clock T is generated at the ELU, both terminals lock to this clock and return the clock T to
the DSL units. An elastic store in the DSLUs buffers the framed data.
Using the “Configuration > User Port” Menu:
1. At the ELU, select the ‘Internal’ timing option
2. Using F8, cycle to the NTU user port, select the ‘Internal’ timing option
3. Press ‘Return’ to enter the changes.
4.7.1.1.2 G.703 to G.703 Transparent Timing
One of the connected terminals acts as a master, the other is a slave. However, both terminals could
operate independently or pleisiochronously.
T1
T2
Terminal 1
T2
ELU
NTU
T1
Terminal 2
Clocks T1 and T2 are independent of one another and are transported independently through the
DSL system.
Using the “Configuration > User Port” Menu:
4. At the ELU, select the ‘Transparent’ timing option
5. Using F8, cycle to the NTU user port, select the ‘Transparent’ timing option
6. Press ‘Return’ to enter the changes.
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4.7.1.1.3 X.21/V.35 DCE to X.21/V.35 DCE
The terminals connected to the digital section at both ends are DTEs, a clock inside the ELU then
becomes the reference clock for the entire system.
T
T
Terminal 1
ELU
NTU
DCE
DCE
T
Terminal 2
4.7.1.2 Tandem Section
For the following configurations, the DSLUs are connected in series with another transmission system
or equipment
ELU
Network
NTU
Terminal 2
Terminal 1
4.7.1.2.1 G.703 to G.703 Transparent Timing
The timing for each terminal is carried independently across the digital section.
T1
T1
Network
Terminal 1
T2
T2
ELU
NTU
T2
T1
Terminal 2
Using the “Configuration > User Port” Menu:
7. At the ELU, select the ‘Transparent’ timing option
8. Using F8, cycle to the NTU user port, select the ‘Transparent’ timing option
9. Press ‘Return’ to enter the changes.
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4.7.1.2.2 X.21/V.35 DTE-to X.21/V.35 DCE
The plug in module at the master end of the digital section must be configured as a DTE. This allows
timing to be recovered from the timing output from the tandem system.
T
Network
Terminal 1
19
ELU
NTU
DTE
DCE
T
T
Terminal 2
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4.7.2 Point to Multipoint Link
Note, when operating in Point to Multipoint, the master unit always has a G.703 user interface.
The slave units may be
EITHER all G.703
OR all Datacom (any mixture of X.21 and V.35).
4.7.2.1 Standalone Section
NTU
T
Terminal 1
T
T
T
ELU
NTU
T
Terminal
Terminal 2
G.703
NTU
T
Terminal 3
4.7.2.1.1 G.703 to G.703
A clock ‘T’ inside the master DSL unit provides the reference clock for the entire system.
Using the “Configuration > User Port” Menu:
10. At the ELU, select the ‘Internal’ timing option
11. Using F8, cycle through the remote user ports, selecting the ‘Internal’ timing option
12. Press ‘Return’ to enter the changes.
4.7.2.1.2 G.703 to X.21/V.35
A clock inside the master DSL unit provides the reference clock for the entire system.
Using the “Configuration > User Port” Menu:
1. At the ELU, select the ‘Internal’ timing option
2. Press ‘Return’ to enter the changes.
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AM768A/AM2048A
4.7.2.2 Tandem Section
NTU
T
Terminal 1
T
Network
Terminal
T
ELU
NTU
T
T
Terminal 2
G.703
NTU
T
Terminal 3
4.7.2.2.1 G.703 to G.703
The master DSL unit locks on to the incoming clock ‘T’, this clock is passed to the remote terminals 1,
2 and 3.
Using the “Configuration > User Port” Menu:
1. At the ELU, select the ‘transparent’ timing option
2. Using F8, cycle through the remote user ports, selecting the ‘Internal’ timing option
3. Press ‘Return’ to enter the changes.
4.7.2.2.2 G.703 to X.21/V.35
The master DSL unit locks on to the incoming clock ‘T’, this clock is passed to the remote terminals 1,
2 and 3.
Using the “Configuration > User Port” Menu:
1. At the ELU, select the ‘transparent’ timing option
2. Press ‘Return’ to enter the changes.
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AM768A/AM2048A
4.8 Bringing into Service
Once the equipment is correctly installed, it may be necessary to monitor the quality of service before
putting live traffic on the circuit, depending on the installation rules of the network.
The AM2048 has various features which help the user to do this with a high degree of confidence
without the use of extra test equipment. A terminal plugged into the ELU gives access to the following
information:
In the “Performance > m.2100” History screen, the display records errored seconds, severely errored
seconds and unavailable seconds for the aggregate line system. The recording interval and the pass
fail criterion of the datalog record is programmable by the user to match the tables found in m.2100.
In the “Performance > Transmission Line” screen, the display records G.826 statistics for both ends of
each transmission line. In a multi pair system, if errors are recorded in the m.2100 screen, this screen
will help to locate the erroring line and direction of errors.
Once the circuit is working, the “Alarm > History” screen should be checked and cleared. The alarm
history should be checked after a suitable interval to ensure that no alarms are occurring.
(For more details of the menu system see the “VT100 Management User Guide for the AM2048.”)
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AM768A/AM2048A
4.9 Transmission Parameters
4.9.1 Transmission Range
4.9.1.1 Copper Transmission Systems
For the copper transmission systems, the equipment is designed to meet the performance limits
specified in ETR 152. This specification defines bit error rate performance for DSL systems in the
presence of noise over a variety of cable loops.
Note: For the tables below, baseline performance is measured on 0.4mm Polyethylene Twin cable.
Figures for other cable diameters are based the 0.4mm performance and extrapolated using typical
cable characteristics.
4.9.1.1.1 AM2048 MP – 2048kbps over 3 pairs
Attenuation of 31dB at 150kHz, with noise present, gives a BER of <1 x 10 E-7.
Cable diameter
(mm)
0.4
0.5
0.63
0.9
Range with noise
(km)
2.8
3.73
5.19
8.00
Range, without noise
(km)
3.5
4.67
6.48
10.00
4.9.1.1.2 AM2048 CAP – 2048kbps over 2 pairs
Attenuation of 31dB at 150kHz, with noise present, gives a BER of <1 x 10 E-7.
Cable diameter
(mm)
0.4
0.5
0.63
0.9
Range with noise
(km)
2.8
3.73
5.19
8.00
Range, without noise
(km)
4.0
5.33
7.41
11.43
4.9.1.1.3 AM2048 CAP – 2048kbps over 1 pair
Attenuation of 23dB at 150kHz, with noise present, gives a BER of <1 x 10 E-7.
Cable diameter
(mm)
0.4
0.5
0.63
0.9
23
Range with noise
(km)
2.0
2.67
3.70
5.71
Range, without noise
(km)
3.0
4.00
5.56
8.57
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AM768A/AM2048A
4.9.1.2 Optical Transmission
The system operates from 0dB to 25dB of optical attenuation.
For single-mode (9/125) fibre with an attenuation of 0.35dB/km this equates to a transmission
distance up to 70km.
For multi-mode (50/125 or 62.5/125) fibre with an attenuation of 0.6dB/km this equates to a
transmission distance up to 41km.
Attention! Care must be taken to ensure that the fibre connectors are clean.
4.9.2 End to End Delay
The transit delay from one end of the system to the other is < 700uS.
4.9.3 Jitter
For G.703 interfaces, the jitter meets the requirements of TBR12 and TBR13.
Measurement Filter Bandwidth
Lower Cut Off (High Pass)
40Hz
Upper Cut Off (Low Pass)
100kHz
Output Jitter
UI Peak to Peak (maximum)
0.11
These measurements are performed in the presence of the maximum tolerable input jitter.
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4.10 G.703 Interface Options
4.10.1 Unstructured Operation
CRC4
HDSL
CRC4G
FAW
A
SA4
SA5
SA6
SA7
SA8
Tx
TS0
TS0
CRC4M
Rx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC6
HDSL
CRC4M
TS0
TS0
Rx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC4G
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC6
TE
NT1
LT
T
V3
ET
Figure 4 : Unstructured Operation
For unstructured working, Loss of Frame Alignment and AIS alarms are suppressed. The user data
passes transparently through the system. An arbitrary frame position is assumed for mapping the user
data in to the line pairs.
The user data may or may not have TS0, and may or may not be using CRC4, nothing is assumed
about the user data.
To set up this configuration, go to the “Configuration > User Port” Menu and select
Rx Unframed
Rx Framed
Rx CRC4
Tx TSO Transparent
Tx TSO Generate
Tx CRC4
25
(*)
( )
[ ]
(*)
( )
[ ]
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AM768A/AM2048A
4.10.2 Structured Operation
CRC4
CRC4G
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
HDSL
TS0
Rx
E
CRC4M
TS0
Rx
CRC6
CRC4M
FAW
A
SA4
SA5
SA6
SA7
SA8
Tx
TS0
Rx
FAW
A
SA4
SA5
SA6
SA7
SA8
E
HDSL
Tx
TS0
Rx
CRC4G
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC6
TE
NT1
T
LT
V3
ET
Figure 5 : Structured Working, End to End transparent CRCs
For fractional working where not all pairs are equipped, the G.704 frame is padded out with the
programmable ‘Idle’ pattern.
To set up for structured working with transparent CRCs, go to the “Configuration > User Port” Menu
and select
Rx Unframed
Rx Framed
Rx CRC4
Tx TSO Transparent
Tx TSO Generate
Tx CRC4
( )
(*)
[ ]
(*)
( )
[ ]
The incoming structured data may be monitored for CRC4 errors, however, no E bits are returned at
the user interface from the transmission equipment. To do this, simply enable the Rx CRC4 checkbox.
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AM768A/AM2048A
4.10.3 Structured Working, CRCs Enabled
CRC4
CRC4
CRC4G
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC4M
TS0
E
CRC4G
Tx
E
CRC4M
FAW
A
SA4
SA5
SA6
SA7
SA8
HDSL
Rx
TS0
Rx
CRC6
CRC4G
HDSL
CRC4M
TS0
Rx
E
E
CRC4M
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
TS0
Rx
CRC4G
Tx
FAW
A
SA4
SA5
SA6
SA7
SA8
CRC6
TE
NT1
LT
T
V3
ET
Figure 6 : Structured Working, CRCs Enabled
In this case, the CRCs are checked and errored blocks are indicated back across the user interface
by use of the E bits.
This is the least ambiguous mode of operation from a performance monitoring point of view because
each transmission section is covered by its own independent CRC check.
To set up this configuration, go to the “Configuration > User Port” Menu and select
Rx Unframed
()
Rx Framed
(*)
Rx CRC4
[X]
Tx TSO Transparent
()
Tx TSO Generate
(*)
Tx CRC4
[X]
In this mode of operation, the test loop activation messages defined in ETS 300 233 are passed to
and from the LT over the V3 interface.
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4.10.4 ETS 300 233 Loopbacks
Loop 1 and Loop2 may be activated by sending patterns using spare bits 5 and 6 in TS0.
Loopback 1
ELU
Network
NTU
Loopback 2
ELU
Network
NTU
Table 1 CrC4 Multiframe Structure
Submultiframe
I
Multiframe
II
28
Frame
number
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
1
c1
0
c2
0
c3
1
c4
0
c1
1
c2
1
c3
E
c4
E
2
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Bits 1 to 8 of the PCM frame (i.e. time slot 0)
3
4
5
6
7
0
1
1
0
1
A
Sa4
Sa5
Sa61
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa62
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa63
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa64
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa61
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa62
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa63
Sa7
0
1
1
0
1
A
Sa4
Sa5
Sa64
Sa7
8
1
Sa8
1
Sa8
1
Sa8
1
Sa8
1
Sa8
1
Sa8
1
Sa8
1
Sa8
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AM768A/AM2048A
Table 2 Loopback code definitions
State
Loopback 1 command
Loopback 2 command
Loopback acknowledge
Loopback
release
command
DS-ET
<-<--->
<--
Sa5
0
0
0
0
Sa6
1111
1010
XXXX
0000
These loop activation codes are only detected at the G.703 interface at the ELU when CRCs are
enabled.
Loop 1 is the equivalent of a local loop at the ELU.
Loop 2 is the equivalent of a remote loop set from the ELU.
Note, the specification did not anticipate point to multipoint so in this mode loop 2 is not meaningful.
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5. Physical Interfaces
5.1 Mains Power Supply
If a 48V DC power supply is not available, mains to 48V converters are available.
5.1.1 240V Plug Top PSU
This unit is a basic UK plug top with two core screened cable terminated in a 3 way mini-fit connector.
Lead length 1.8m
Ascom part number
5/500/000/037
5.1.2 240V In Line PSU
On this unit, the mains connector is a standard 3 pin IEC 320 input.
Lead length 1.8m
Ascom part number
5/500/000/041
5.1.3 110V In-line PSU
On this unit, the mains connector is a standard 3 pin IEC 320 input.
Lead length 1.8m
Ascom part number
5/500/000/038
5.2 DC Power inlet
DC power is fed in via the three pin socket on the rear panel.
1
2
3
1
-48V
2
0V
3
CGND
A connection from CGND to earth is required for ESD protection of the unit.
If the unit is line powered, the ground connection must be made to the earth bonding point on the rear
panel. (M3 screw)
Mating connector
Molex Minifit Junior Receptacle
Molex female contact
Molex Part Number: 39-01-4031
Molex Part Number: 39-00-0039
The DC Power Cable can be ordered from Ascom, Ascom Part Number (See Appendix B)
CABLE AM2048A DC POWER
6/910/000/423
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5.3 Copper Transmission Line
The line interface connector on the unit is an 8-way RJ45 socket.
PANEL VIEW
1
2
3
4
5
6
7
8
1
Line 1 A
2
Line 1 B
3
n.c.
4
Line 2 A
5
Line 2 B
6
n.c.
7
Line 3 A
8
Line 3 B
The line cable supplied is a standard 3 metre screened Category 5 cable with an 8 way RJ45 plug on
each end.
Ascom part number
6/910/000/425 (See Appendix B)
5.4 Optical Transmission Line
The rear panel optical connector is either FC/SPC, ST or SC. For ordering information see Appendix
B. Connectors plugged into this port should be clean and should have a return loss better than –35dB.
The dust cap should be fitted when the unit is not connected to the line. The optical output from this
port is –5dBm (±2dB) at 1310nm.
5.5 Serial Control
A VT100 compatible terminal can be plugged into the 9-way D-type on the rear panel.
The socket is wired to allow a straight connection to a PC serial port. The serial cable must have pins
2, 3, 4, 5 and 6 connected.
For a full description of the menu system, refer to the ‘VT100 Management User Guide’.
The serial port setting is 19.2Kbaud/s, 8 bit, no parity, 1 stop bit, Xon/Xoff flow control.
The RS232C interface complies with the CCITT V24/V28 standards. The maximum length of cable
between communicating devices is limited to 15.2m (50ft).
Pin #
1
2
3
4
5
6
Function
Receive cct 104
Transmit cct 103
DTR
Ground cct 102
DSR
The serial control cable can be ordered from Ascom, (See Appendix B)
Serial Cable AssemblyAscom Part Number
CABLE 9 WAY SERIAL
6/910/000/429
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AM768A/AM2048A
5.6 Alarm Input/Output Port
The alarm port provides 6 logic level inputs, and the contacts of two changeover relays. The pinout is
shown below:
PANEL VIEW
4
3
2
1
5
6
7
8
12
11
10
9
13
1
RELAY 1 CLOSED = Urgent Alarm
2
RELAY 1 COMMON
3
RELAY 1 OPEN = Urgent Alarm
4
RELAY 2 CLOSED = Non-Urgent Alarm
5
RELAY 2 COMMON
6
RELAY 2 OPEN = Non-Urgent Alarm
7
ALARM INPUT 1
8
ALARM INPUT 2
9
ALARM INPUT 6
10
ALARM INPUT 5
11
ALARM INPUT 4
12
ALARM INPUT 3
13
GND
Figure 7 - Alarm Connector
In the de-energised state, the urgent alarm relay closes the contact between pins 1 and 2 (pins 2 and
3 are open) and the non-urgent alarm relay closes the contact between pins 4 and 5 (pins 5 and 6 are
open).
When power is applied and all alarms are off, the urgent alarm relay opens the contact between pins
1 and 2 (pins 2 and 3 are closed), the non-urgent alarm relay opens the contact between pins 4 and 5
(pins 5 and 6 are closed).
In the ELU, the alarms relay outputs may be used to integrate the AM2048 into the exchange alarm
system.
To save power in the NTU the alarm relays are disabled.
The alarm inputs are available at both the ELU and the NTU and may be used for alarm collection
from other equipment, e.g, door open alarm, battery low alarm, temperature alarms etc. The alarm
inputs detect a short circuit between the alarm input pin and GND (pin 13)
Mating connector CONN 13 WAY PLG
Screened Cable AssemblyCABLE AM2048A ALARM
(See Appendix B)
32
Ascom Part Number
6/313/000/002
Ascom Part Number
6/910/000/424
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AM768A/AM2048A
5.7 Interface Modules
5.7.1 G.703
The 75 ohm interface connectors are BNC.
The 120 ohm interface connector is RJ45.
Selection of the interface is carried out in the “Configuration > User Port” menu.
Fixing Screws
PCB Position
G703 75/120 PIM
120 ohm
75 ohm OUT
75 ohm IN
Card Extractor Grip
RJ45
1
33
2
3
4
5
6
7
8
1
TxA
2
TxB
3
screen
4
RxA
5
RxB
6
screen
7
n.c.
8
n.c.
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AM768A/AM2048A
5.7.2 X.21
V11 refers to ISO 4903 for the connector pin-out.
Circuit
Interchange Circuit Name
G
T
R
C
Signal ground or Common Return
Transmit
Receive
Control
Pins
A…..B
8
2
9
4
11
3
10
I
Indication
5
12
S
Signal Element Timing
6
13
B
Byte Timing
7
14
X
DTE Signal Element Timing
7
14
Definition
From DTE to DCE
From DCE to DTE
From DTE to DCE
ON during Data
OFF during Control
From DCE to DTE
ON during Data
OFF during Control
From DCE to DTE
T and R change at
OFF to ON of S
From DCE to DTE
OFF for the ON period of S
During the last bit of the octet
MK I, not used.
MK II, From DTE to DCE
The clock rate is set up using the “Configuration > User Port” Menu.
Select the required value of N for Nx64K circuits.
DTE – DCE mode, and X-B mode are selected using the hardware links on the X.21 interface module.
Note: X-B is only available on the X.21 MK II Plug In Module.
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5.7.3 V.35
V.35 refers to ISO 2593 for the connector pin out.
Circuit
Interchange Circuit Name
Pins
B
B
P
S
R
T
C
Definition
A
102
103∅
104∅
105
Signal ground or Common Return
Transmitted Data
Received Data
Request To Send (RTS)
106
Ready For Sending (RFS)
D
107
Data Set Ready (DSR)
E
109
Received Signal Detector
F
113∅
Terminal Signal Element Timing
U
114∅
Transmitter Signal Element Timing
Y AA
115∅
Receiver Signal Element Timing
V
W
X
From DTE to DCE
From DCE to DTE
ON transmit Data
OFF transmit binary 1.
ON DCE ready to accept data
OFF DCE not ready
ON DCE ready to operate
OFF DCE not ready to operate
ON line signal is good
OFF line signal out of limits
103 changes at
OFF to ON of 113
103 changes at
OFF to ON of 114
Centre of bit on 104
ON to OFF on 115
140
Remote Loopback
N
141
Local Loopback
L
142
Test Indicator
NN
Circuits marked ∅ are balanced V.35, unmarked circuits are to V.28
Circuit marked is only implemented in DTE mode.
The clock rate is set up using the “Configuration > User Port” Menu.
Select the required value of N for Nx64K circuits.
DTE – DCE mode may be selected using Links 1 and 2.
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5.8 Front Panel
5.8.1 Controls
5.8.1.1 Setting Master/Slave
1. Press the local loop and loopback buttons together and hold them until both the local loop and
loopback indicators are lit. Upon releasing the buttons, the Remote Loop indicator starts to flash
and you have 5 seconds to select and accept the required Master /Slave mode.
2. With the remote loop indicator flashing, press the remote loop button to toggle the state of the
Master/Slave LED. Select Master/Slave as desired.
3. To accept the change, press local loop and loopback buttons together until the Remote Loop
indicator goes off. The unit will then automatically restart in the selected mode.
4. If the change is not accepted within 5 seconds, the Remote Loop indicator will stop flashing and
the unit will leave the programming mode and return to normal operation, with its Master/Slave
mode unchanged.
5.8.1.2 Resetting to Factory Default Configuration
Press the Local Loop and Loopback buttons together, then with the buttons still pressed, press the
remote loop button as well. The unit will automatically restart with all of its configuration data cleared.
Note, when the units reboots it will be configured as a “Slave”.
5.8.1.3 Setting Loops
The following test loops may be set using the front panel buttons.
• Local Loop
• Loopback
• Remote Loop
N.B. These buttons may be disabled from the ‘Test > User Port’ menu.
User
Local Loop
User
Loopback
User
Remote Loop
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5.8.2 Indicators
Power (Green)
This will always be illuminated whenever the unit is powered up.
Test (Red)
This will be illuminated whenever:
the unit has a loop locally or remotely applied.
the unit is applying a remote loop.
the unit is running a data test.
Non-Urgent Alarm (Yellow)
This LED will be illuminated if an alarm of fault severity 2 or 3 is present on the unit
Urgent Alarm (Red)
This LED will be illuminated if an alarm of fault severity 4 or 5 is present on the unit
Master (Green)
When lit, this LED indicates the unit has been configured to operate as a ‘master’. The default setting
is for the unit to be a ‘slave’ in which case the LED will be off.
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6. Internal Links and Fuses
6.1 G.703 Plug In Module
The following diagrams show the location of the internal hardware links.
In all cases the factory default setting is shown on the left.
FS1
FS1
FS4
FS2
FS3
Cap to Ground
FS4
FS2
FS3
Direct to Ground
The 75ohm G.703 receiver and the 120 ohm cable screen may be optionally connected directly to
ground or to ground via a capacitor. The fuses FS1 to FS4 are used to protect the circuit against the
transverse application of mains.
6.2 X.21 Plug In Module MK I
The X.21 module may be configured as a DCE or DTE.
In both modes, the receive clock, data and byte timing circuits may be terminated in 120 ohms.
DCE
38
Load
Out
DTE
Load
In
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AM768A/AM2048A
6.3 X.21 Plug In Module MK II
The X.21 module may be configured as a DCE or DTE.
The 120 termination is always in.
DCE
X
DTE
B
In DCE mode, the module may be configured to generate Byte Timing (B) or receive the DTE clock
(X).
In DTE mode, the module may be configured to receive Byte Timing (B) or generate a DTE clock (X).
6.4 V.35 Plug In module (MK I and MK II)
The V.35 module may be configured as a DCE or DTE. Both links must be in the correct position. If
the links are incorrectly set, the unit will detect the illegal setting.
DCE
39
DCE
DTE
DTE
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AM768A/AM2048A
6.5 Motherboard
Link J1 is factory fitted in the ‘PWR Fed’ position.
This means that the unit can be powered directly from line (for copper transmission systems) or from
the DC input.
The other position for the link is for future use.
The fuse FS400 is a 1A slow blow fuse to protect the DC input.
CON9
CON2R
CON2L
J1
PWR Fed
CON1
Wetting
TIF 1
PSU
CON4R
TIF 2
CON3
TIF 3
CON5
CON4L
CON6R
CON7
CON6L
PIM
FS400
Figure 8 Motherboard Link Settings
CON12
CON8
CON10
CON11
WARNING
Only authorised personnel are allowed to open the DSL System case to change the link
settings. Misuse or any modifications carried out to this unit other than in accordance with the
instructions supplied, will invalidate the guarantee and CE compliance.
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7. Compliance Notes
TTE network statements and the declaration to conformity to EC directive 1999/5/EC are provided
inside the front cover of this User Guide together with safety information.
7.1 Telecommunication Standards
The equipment is in conformity with the following Common Technical Regulations and National
Standards:
Common Technical Regulations
CTR2
CTR12
CTR13
X.21, X.21bis (V.35)
G.703 2Mbps, 120Ω, unstructured
G.703 2Mbps, 120Ω, structured
UK National Standards
NTR4
NTR14
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G.703, 75Ω
Analogue Baseband
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AM768A/AM2048A
8. Glossary
A
AC
AIS
BT
CAP
CCITT
CRC4
CRC6
CRC6G
CRC6M
DC
DCE
DS
DSP
DSL
DSLU
DTE
E bit
ELU
EMC
EN 41003
Alarm bit in G.704 frame, timeslot 0
Alternating Current
Alarm Indication Signal
British Telecom
Carrierless Amplitutde and Phase Modulation
International Telegraph and Telephone Consultative Committee
Cyclic Redundancy Check 4 (bits)
Cyclic Redundancy Check 6 (bits)
CRC6 Generator
CRC6 Monitor
Direct Current
Data Circuit Terminating Equipment
Digital Section (Line section including ELU and NTU)
Digital Signal Processing
Digital Subscriber Line
Digital Subscriber Line Unit. (AM768, AM2048 CAP, AM2048 OS etc.)
Data Terminating Equipment
Bits in the G.704 frame used to indicate that a CRC has been received in error.
Exchange Line Unit
Electromagnetic Compatibility
Particular Safety Requirements for Equipment to be connected to Telecommunications
Networks
EN 60950
1992. Up to A11 (1997) Safety of Information Technology Equipment.
EOC
Embedded Operations Channel
ESD
Electro Static Discharge
ET
Exchange Termination
ETR152
ETSI Technical Report 152 (1996).Transmission and multiplexing; DSL transmission
system on local lines;
ETS
European Telecommunications Standard
FAW
Frame Alignment Word
FIFO
First In First Out Buffer
FLASH
Nonvolatile read/write memory
G.703
CCITT Recommendation G.703 (1988): “Physical/electrical characteristics of
hierarchical digital interfaces”.
G.704
CCITT Recommendation G.704 (1988): “Synchronous frame structures user at primary
and secondary hierarchical levels”.
G.706
CCITT Recommendation G.706 (1988): “Frame alignment and CRC procedures
relating to basic frame structures defined in G.704”
G.826
CCITT Recommendation G.826 (1996) “Error performance parameters and objectives
for international, constant bit rate digital paths at or above the primary rate”
HD 384
Electrical Installation of Buildings (IEC 60364 series, modified)
IC
Integrated Circuit
IEC 61312-1 Protection against lightning electromagnetic impulse; Part 1 General Principals
ISO
International Standards Organisation
LED
Light Emitting Diode
LT
Line termination (Same as ELU)
LVD
Low Voltage Directive
M.2100
CCITT recommendation M.2100 (1995) Performance limits for bringing into service and
maintenance of international PDH paths, sections and transmission systems.
NT
Network Termination
NTU
Network Terminating Unit
NTP
Network Termination Point
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PC
PCB
PCM
RAM
SAn
SELV
SNMP
TE
TSn
TNV
VT100
V11
V.35
X.21
3B1O
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AM768A/AM2048A
Personal Computer
Printed Circuit Board
Pulse Code Modulation
Random Access Memory
G.704 Timeslot 0 spare bit n.
Safe Extra Low Voltage
Simple Network Management Protocol
Terminal Equipment
Timeslot n
Telecommunications Network Voltage
Industry standard character based terminal.
CCITT Recommendation V.11 Electrical characteristics for balanced double-current
interchange circuits for general use with integrated circuit equipment in the field of data
communications
CCITT Recommendation V.24 List of definitions for interchange circuits between DTE
and DCE
CCITT Recommendation X.21 Interface between DTE and DCE for synchronous
operation public data networks.
Line code where 3 binary bits are coded into 8 (octal) discrete levels.
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AM768A/AM2048A
9. Troubleshooting
Please check the following points if problems are experienced setting up a DSL link:
1. For the copper system, ensure the modem is being used on unconditioned twisted pairs.
2. For the copper system, check the correct pin connections are being used on the RJ45 line
connector.
3. For the optical system, if problems are experienced with ‘Loss of Sync’ check that the optical
connector is clean. On a single fibre system, the transmission may be sensitive to back reflections
caused by dust in the connector.
4. Check that one DSLU is set to master and the other(s) to slave.
5. Check that no test loops are active. (The front panel TEST LED should be off on all units).
6. Using the Management Terminal,
a) Check the “Information > System” screen for user port settings ie. DTE/DCE mode.
b) Check the “Alarms > Status” screen for details of any faults.
c) Check the “Configuration > Master/Slave” mode for general system settings.
d) Check the “Configuration > User Port” for user clock rate settings.
7. For G.703 interfaces. If CRCs are enabled and only one copper pair is being used for
transmission, ensure that the idle pattern is set correctly in the “Configuration>User Port” Screen.
8. For nx64k check that the correct value of ‘n’ has been selected at BOTH ends of the link.
If there is a doubt, enter the Configuration> User Port Screen and press ‘Enter’.
9. For nx64k, check the DCE-DTE cable length against the charts in Appendix A.
10. If the front panel test loops fail to operate, check to see if they are enabled in the “Test > User
Port” screen, also check that no conflicting tests are already activated.
For persistent problems please contact your local distributor for assistance.
Ascom Transmission technical support is available by fax on +44 29 20 500 850 in the first instance.
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AM768A/AM2048A
Appendix A - X.21/V.35 Cable lengths
There is an inherent design limitation with the X.21 and V.35 interfaces when timing information is
only transmitted in one direction.
The timing is usually sent from the DCE to the DTE. Data originating from the DCE and travelling to
the DTE arrives at the DTE with the same clock skew with which it originated at the DCE. However,
data originating at the DTE arrives back at the DCE skewed relative to the DCE clock. This skew is
equal to (2 x cable delay) + Driver delays at both ends.
Receive data is normally sampled at the half bit period position. So to guarantee correct operation,
the data arriving at the DCE must avoid this half period delay.
NB. This calculation is only valid If the DTE samples receive data at the half bit position.
Example calculation:
Note: The driver delays for the DTE are only ESTIMATED values.
For N = 32
Bit period = 488ns
Half period = 244ns
Typical V11 driver delay = 30ns
Typical logic delay = 8ns
Typical cable delay per metre = 6ns
1st problem cable delay
1st problem cable length
Total driver delay = driver delay x 4 = 120ns
= (Half Bit Period – total driver delays – logic delay)/2
= (244 – 120 – 8 /2
= 58ns
= 9.7m
2nd problem cable length = (one and a Half Bit Period – total driver delays – logic delay)/12
= (732 – 120 - 8)/12
= 50.3m
3rd problem cable length = (two and a Half Bit Period – total driver delays – logic delay)/12
= (1220 – 120 – 8 )/12
= 91m
And so on…
So, further problem lengths occur at additional
(Bit Period)/(2 x Cable delay per metre) = 40.6m
See the next pages for the potential problem cable lengths for all values of N.
If a problem is experienced, try adding two metres to the cable length.
The latest versions of the X.21 and V.35 interface have features which help to overcome these
problems.
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X.21 Cables - Potential Problem Lengths
Cable Delay per metre (ns)
6
Driver Delay (ns)
30
Logic Delay (ns)
8
N Data Rate Bit Period Max Delay 1st Length
kbps
ns
ns
m
64
15625
3842
1
640.4
128
7813
1889
2
314.9
192
5208
1238
3
206.3
256
3906
913
4
152.1
320
3125
717
5
119.5
384
2604
587
6
97.8
448
2232
494
7
82.3
512
1953
424
8
70.7
576
1736
370
9
61.7
640
1563
327
10
54.4
704
1420
291
11
48.5
768
1302
262
12
43.6
832
1202
236
13
39.4
896
1116
215
14
35.8
960
1042
196
15
32.7
1024
977
180
16
30.0
1088
919
166
17
27.6
1152
868
153
18
25.5
1216
822
142
19
23.6
1280
781
131
20
21.9
1344
744
122
21
20.3
1408
710
114
22
18.9
1472
679
106
23
17.6
1536
651
99
24
16.5
1600
625
92
25
15.4
1664
601
86
26
14.4
1728
579
81
27
13.4
1792
558
76
28
12.6
1856
539
71
29
11.8
1920
521
66
30
11.0
1984
504
62
31
10.3
2048
488
58
32
9.7
46
1302.1
651.0
434.0
325.5
260.4
217.0
186.0
162.8
144.7
130.2
118.4
108.5
100.2
93.0
86.8
81.4
76.6
72.3
68.5
65.1
62.0
59.2
56.6
54.3
52.1
50.1
48.2
46.5
44.9
43.4
42.0
40.7
2nd Length
m
1942.5
965.9
640.4
477.6
380.0
314.9
268.4
233.5
206.3
184.6
166.9
152.1
139.6
128.8
119.5
111.4
104.2
97.8
92.1
87.0
82.3
78.1
74.3
70.7
67.5
64.5
61.7
59.1
56.7
54.4
52.3
50.4
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X21 Cable Length vs N
100.0
90.0
Cable Length in Metres
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
1
4
7
10 13 16 19 22 25 28 31
N
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V.35 Cables - Potential Problem Lengths
Cable Delay per metre (ns)
6
Driver Delay (ns)
50
Logic Delay (ns)
23
N Data Rate Bit Period Max Delay 1st Length
kbps
ns
ns
m
64
15625
3795
1
632.5
128
7813
1842
2
306.9
192
5208
1191
3
198.4
256
3906
865
4
144.2
320
3125
670
5
111.6
384
2604
540
6
89.9
448
2232
447
7
74.4
512
1953
377
8
62.8
576
1736
323
9
53.8
640
1563
279
10
46.5
704
1420
244
11
40.6
768
1302
214
12
35.7
832
1202
189
13
31.5
896
1116
168
14
27.9
960
1042
149
15
24.8
1024
977
133
16
22.1
1088
919
118
17
19.7
1152
868
106
18
17.6
1216
822
94
19
15.7
1280
781
84
20
14.0
1344
744
75
21
12.4
1408
710
66
22
11.0
1472
679
58
23
9.7
1536
651
51
24
8.5
1600
625
45
25
7.5
1664
601
39
26
6.5
1728
579
33
27
5.5
1792
558
28
28
4.7
1856
539
23
29
3.9
1920
521
19
30
3.1
1984
504
15
31
2.4
2048
488
11
32
1.8
48
2nd Length
m
1302.1
1934.5
651.0
958.0
434.0
632.5
325.5
469.7
260.4
372.0
217.0
306.9
186.0
260.4
162.8
225.6
144.7
198.4
130.2
176.7
118.4
159.0
108.5
144.2
100.2
131.7
93.0
120.9
86.8
111.6
81.4
103.5
76.6
96.3
72.3
89.9
68.5
84.2
65.1
79.1
62.0
74.4
59.2
70.2
56.6
66.3
54.3
62.8
52.1
59.5
50.1
56.5
48.2
53.8
46.5
51.2
44.9
48.8
43.4
46.5
42.0
44.4
40.7
42.5
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AM768A/AM2048A
V35 Cable Length vs N
100.0
90.0
Cable Length in Metres
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
1
4
7 10 13 16 19 22 25 28 31
N
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Appendix B – Ordering Information
KEY
User Interfaces
G.703
X=1
X.21
X=2
V.35
X=3
G.703 MK II
X=4
X.21 MK II
X=5
V.35 MK II
X=6
Optical Transmission
Single Mode Fibre
Multimode Fibre
Fibre Connectors
FC/SPC
Y=A
ST
Y=B
SC
Y=C
AM2048A OS
AM2048A OM
Copper Transmission
Three pair, 3B1O
AM2048A MP
Single Pair 3B1O
AM768A
One/Two Pair CAP 1024/2048 AM2048A CAP
Example order code
1/187/536/9AB
Order Code
1/187/50X/9AY (For X and Y, see key)
1/187/53X/9AY
Order Code
1/187/51X
1/187/52X
1/187/56X
AM2048A OM V.35 ST
Optical Transmission
Mutimode fibre
ST connector
User interface V.35 MKII
Spare User Interfaces
G.703
X.21
V.35
G.703 MK II
X.21 MK II
V.35 MK II
ascom part number
2/187/002
2/187/004
2/187/005
2/187/006
2/187/007
2/187/008
Order Code
1/187/002
1/187/004
1/187/005
1/187/006
1/187/007
1/187/008
Power Supplies
240V UK Plug top
240V In Line IEC
110V In Line IEC
ascom part number
5/500/000/037
5/500/000/041
5/500/000/038
Order Code
1/187/311
1/187/312
1/187/313
Accessories
ascom part number
AM2048 DC Cable
5/500/000/037
AM2048 Alarm Connector
6/313/000/002
AM2048 Alarm Cable
6/910/000/424
AM2048 RJ45-RJ45 Cable
6/910/000/425
AM2048 RS232 Cable
6/910/000/429
Management Pack
n.a.
(Includes VTMS Handbook and RS232 cable)
Order Code
1/187/314
1/187/315
1/187/316
1/187/317
1/187/320
1/187/350
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USER GUIDE
AM768A/AM2048A
Issue 8
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