USER
MANUAL
MODEL 2703-X21
G.703/E1 Digital Modem
SALES OFFICE
(301) 975-1000
TECHNICAL SUPPORT
(301) 975-1007
Part# 07M2703-X21-C
Doc# 031111UC
Revised 6/19/98
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An ISO-9001
Certified Company
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3.0 CONFIGURATION
Switch Set S1
The configuration switches on S1 set clocking, rate adaptation,
loopback enable, and data invert. The default settings are
summarized in the table below.
The Model 2703-X21 is equipped with one DIP set containing eight
switches (externally accessible), as well as seven jumpers (internal).
These switches and jumpers allow configuration of clocking, data rate,
and test options. The Model 2703-X21 is also equipped with an internal
switch that allows selection of 115 or 230 VAC power inputs (Note: this
switch is not present in Models 2703-X21-UI and 2703-X21-DC). This
section describes switch and jumper locations and explains all possible
configurations.
S1 SUMMARY TABLE
Position
S1-1
S1-2
S1-3
S1-4
S1-5
S1-6
S1-7
S1-8
Function
Clock Master/Slave
Rate Adaptation
Rate Adaptation
Test Enable
Factory Default
On
Off
Off
Off
Off
Off
Off
Off
Master
3.1 EXTERNAL DIP SWITCH SETTINGS
2.048 Mbps
}
The Model 2703-X21’s DIP switch set is located on the underside
of the unit (see Figure 1, below). Figure 2 (below), shows the
orientation of the switch set. All possible settings for the Model 2703-
X21’s switches are presented in the summary table and descriptions on
the following pages. If you have additional questions regarding
configuration, contact Patton Technical Support at (301) 975-1000.
Front Panel
Not Inverted
N/A
Data Inversion
Not Used
Not Used
N/A
Not Used
N/A
S1-1: Master/Slave Clock
The setting for switch S1-1 determines whether the Model 2703-
X21 provides the master clock, or is slaved to another clock source.
S1
S1-1
On
Off
Setting
Model 2703-X21 is master
Model 2703-X21 is slave, (clock is recovered
from the network)
Figure 1. Underside of Model 2703, showing external DIP switch location
ON
O N
1 2 3 4 5 6 7 8
1 2
OFF
3
4
5
6
7
8
OFF
Figure 2. Close up of configuration switches
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S1-2 and S1-3: Rate Adaptation
3.2 INTERNAL JUMPER SETTINGS
Switches S1-2 and S1-3 are set in combination to allow the Model
2703-X21 to adapt to terminal devices running at data rates of less than
2.048 Mbps (The network rate remains 2.048 Mbps regardless of the
terminal rate adaptation setting). The setting you select should match
the data rate of your terminal device.
The Model 2703-X21’s seven jumpers are located on the PC board
inside the unit. To access the jumpers, follow these instructions:
1. Insert a flat head screw driver into an open slot on either side
of the case, as in Figure 3. Twist the screw driver head slightly
and the top half of the case will separate from the lower half,
as in Figure 4, below.
S1-2
Off
S1-3
Off
Setting
2.048 Mbps
1.024 Mbps
512 kbps
256 kbps
On
Off
2. Remove the Network Interface Module by lifting gently upward
on it until it comes free from the Model 2703-X21 main PC
board.
Off
On
On
On
NOTE: Revision B Firmware (or newer, Implemented 6/19/98)
has been adopted to correct signal polarity at 1.024 Mbps, 512
kbps, and 256kbps. To operate Revision B Firmware units with
Revision A (or older) units at one of these sub-rates, you must
invert invert the data (Switch S1-5 On. See Below) (Firmware
revision level is printed on the label on the bottom of the unit).
3. Slide out the Network Interface Module and locate the jumpers
on the bottom side of the board.
4. Configure the jumpers according to the section below and
return the Network Interface Module and cover to their proper
positions.
S1-4: Loopback Test Enable
Depending upon the setting of switch S1-4 the Model 2703-X21 will
either be continually in loopback mode, or loopback mode will be
enabled by pressing and holding the front panel switch. Since the
front panel switch is spring loaded–it returns to “Normal” operation
when pressure is released–this DIP switch provides a way of leaving
the Model 2703-X21 in “unattended” loopback mode for remote test
purposes.
Figure 3. Opening the 2703 Case with a Small Screwdriver
S1-4
On
Off
Setting
Continual “unattended” loopback mode
Loopback activation by front panel switch
S1-5: Data Inversion
The setting for switch S1-5 determines whether or not the data
stream from the local DTE is inverted within the Model 2703-X21 before
being passed to the G.703 network. The ability to invert the data
stream may be necessary when the Model 2703-X21 is being used with
an embedded G.703 device that inverts the data on the remote end.
Normally, data inversion is not necessary.
Figure 4. Opening the 2703 Case With a Small Screwdriver
S1-5
On
Off
Setting
Data inverted
Data not inverted
The internal jumpers mounted on the Model 2703-X21’s PC board
(labeled LK1 - LK7) are used to configure the 75 ohm or 120 ohm
network link parameters. Figure 5 (below) shows the location of the
Model 2703’s jumpers on the internal PC board.
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S1-6, S1-7 & S1-8 Not Used
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LK1: 75 Ohm Transmit Shield-to-Ground Connection
This setting determines whether the shield of the 75 Ohm (coax)
transmit cable is connected to earth ground. This connection must be
made when operating in 75 Ohm (unbalanced) mode. Conversely, this
connection must not be made when operating in 120 Ohm (balanced)
mode.
LK2
LK6
LK7
LK5
LK3
LK1
Strap On
Strap Off
Setting
75 Ohm TX Shield-to-GND Connection Made
75 Ohm TX Shield-to-GND Connection Broken
LK2: 75 Ohm Receive Shield-to-Ground Connection
LK4
LK1
This setting determines whether the shield of the 75 Ohm (coax)
receive cable is connected to earth ground. This connection is optional
when operating in 75 Ohm (unbalanced) mode. This connection must
not be made when operating in 120 Ohm (balanced) mode.
Figure 5. Jumper locations on Model 2703 PC board.
LK2
Strap On
Strap Off
Setting
The table below shows the factory default jumper settings.
Following the table are descriptions for each jumper.
75 Ohm RX Shield-to-GND Connection Made
75 Ohm RX Shield-to-GND Connection Broken
JUMPER SUMMARY TABLE
Jumper
Function
75 ohm 120 ohm Factory Default
LK3: DIP Switch S1-1 Enable
LK1
75 Ohm TX Shield to GND
On
Off
Off
On (connect)
Off (disconnect)
Off
This strap is reserved for future use and must remain Off.
LK2 75 Ohm RX Shield to GND Opt.*
LK3
Setting
LK3
LK4
LK5
LK6
LK7
Reserved
Strap On
Strap Off
Not a Valid Setting
Normal Setting
120 Ohm Shield to GND
Configuration Auto-Sense
75 Ohm Input Impedance
75 Ohm Input Impedance
Off
On
On
On
Opt.
Opt.
Off
Off (disconnect)
On (enabled)
LK4: 120 Ohm Shield-to-Ground Connection
On (75 Ohm)
}
Off
This setting determines whether the shield of the 120 Ohm
(modular) cable is connected to earth ground. This connection is
optional when operating in 120 Ohm (balanced) mode. This connection
must not be made when operating in 75 Ohm (unbalanced) mode.
*Opt. = optional setting, all others are required for proper operation
NOTE: one combination of jumper settings is required for 75 ohm
operation, and another combination is required for 120 ohm
operation. The Model 2703 is factory configured for 75 ohm
operation.)
LK4
Setting
Strap On
Strap Off
75 Ohm RX Shield-to-GND Connection Made
75 Ohm RX Shield-to-GND Connection Broken
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LK5: Configuration Auto-Sense
3.3 POWER SUPPLY OPTIONS
This setting determines whether the host can automatically sense
the configuration of the Applique. The operation of the Applique is not
affected by this jumper setting. Auto-sense should be enabled when
operating in 75 Ohm (unbalanced) mode. Current interface standards
do not list this feature for 120 Ohm (balanced) mode.
The Model 2703-X21 is available with three power supply options:
The Standard power supply option (Model 2703-X21 or 2703-X21-
230) is factory configured for either 115 or 230 VAC, depending on
how the product is ordered, and is available with a variety of
domestic and international power cords (see Appendix C).
LK5
Strap On
Strap Off
Setting
Auto-sense enabled
Auto-sense disabled
The Universal Interface power supply option (Model 2703-X21-UI)
operates in environments ranging from 85 to 265 VAC, with no re-
configuration necessary (see Appendix C for available domestic
and international power cords).
LK6 & LK7: 75 Ohm Termination Impedance
The DC power supply option (Model 2703-X21-DC) operates in 48
VDC environments and is equipped with a 3-pin “terminal strip”
style DC power cord.
This jumper sets the termination impedance correctly for 75 Ohm
operation. Both jumpers must be in place when operating in 75 Ohm
(unbalanced) mode. Conversely, both jumpers must be removed when
operating in 120 Ohm (balanced) mode.
LK6
On
Off
LK7
On
Off
Setting
75 ohm operation
120 ohm operation
WARNING! There are no user-serviceable parts in the
power supply section of the Model 2703-X21. Voltage
setting changes and fuse replacement should only be
performed by qualified service personnel. Contact
Patton Electronics Technical support at (301)975-1007 for
more information.
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4.0 INSTALLATION
4.2 CONNECTION TO THE TERMINAL DEVICE
Once the Model 2703-X21 is properly configured, it is ready to
connect to your system. This section tells you how to properly connect
the Model 2703-X21 to the G.703 network and terminal device
interfaces.
The Model 2703-X21 is wired as a DCE, and–when configured
properly–supports communication with an X.21 DTE device. The Model
2703-X21 is equipped with a DB-15 female connector and uses a
standard X.21 patch cable, wired straight through. If you wish to
construct your own terminal adapter cable, please consult the pinout
diagram in Appendix B.
4.1 CONNECTION TO THE G.703 NETWORK
The Model 2703-X21 supports 2.048 Mbps communication over an
unstructured G.703 network. Both 120 ohm twisted pair and 75 ohm
coax interfaces are provided on the rear panel of the Model 2703-X21
(see Figure 6, below). Be sure the unit is configured properly to operate
in either 120 ohm or 75 ohm mode, and that the network connection is
grounded appropriately (see Section 3.0).
4.3 CONNECTION TO THE POWER SOURCE
As described in Section 3.3, the Model 2703-X21 is available with
three power supply options: two AC and one DC. The two AC power
supply options (Standard and Universal) use a female IEC power cord
interface, for which Patton can supply various domestic and
international power cords. Please refer to Appendix C for specific
Patton part numbers when ordering power cords. The DC power
supply option uses a 3-pin terminal strip interface (Note: Please refer
to the Model 2703-X21 Service Manual for DC power supply wiring
instructions).
(Model 2703-X21-DC has terminal strip)
Network
DTE Interface
Figure 6. Model 2703 rear panel
4.1.1 Twisted Pair (120 OHM) Connection
The Model 2703-X21 is equipped with a single RJ-45 jack for
connection to a 120 ohm twisted pair G.703 network interface. The
pinout of this jack is as follows:
RJ-45 Pins
SIGNAL
1 & 2 . . . . . . . . . . . . Receive pair (from network)
3. . . . . . . . . . . . . . . . Shield reference point
4 & 5 . . . . . . . . . . . . Transmit pair (to network)
6. . . . . . . . . . . . . . . . Shield reference point
7. . . . . . . . . . . . . . . . Not used
8. . . . . . . . . . . . . . . . Not used
4.1.2 Dual Coax BNC (75 OHM) Connection
In addition to the 120 ohm twisted pair connection, the Model 2703-
X21 is equipped with dual female BNCs (TX and RX) for connection to
a 75 ohm dual coax G.703 network interface. The outer conductor of
the coax cables is isolated from system earth ground.
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5.0 OPERATION
5.3 LOOPBACK TEST (LAL)
Once the Model 2703-X21 is properly configured and installed, it
should operate transparently. This sections describes power-up,
reading the LED status monitors, and using the built-in loopback test
modes.
The Model 2703-X21 is equipped with a Local Analog Loopback
(LAL) mode to assist in evaluating the operation of the local Model
2703-X21. Any data sent to the local Model 2703-X21 in this test mode
will be echoed (returned) back to the user device. For example,
characters typed on the keyboard of a terminal will appear on the
terminal screen. To perform a LAL test, follow these steps:
5.1 POWER-UP
To apply power to the Model 2703-X21, first be sure that you have
read Section 3.3, and that the unit has the proper voltage setting and
fuse. Failure to do so could result in damage to the unit and connected
equipment, and may constitute a fire hazard. Having checked the
voltage setting, plug the AC power cord into both the Model 2703-X21
and the AC outlet. Then Power-up the unit using the rear Power switch.
Note: the “PWR” LED should glow when power is applied to the unit.
A. Activate LAL by moving the front panel toggle switch UP and
holding it in the “Loopback” mode. The “Loop” LED should glow. Once
LAL is activated, the Model 2703-X21 transmit output is connected to its
own receiver.
Note: The front panel switch is spring loaded, so it will return to
“Normal” operating mode when pressure is released. To put the Model
2703-X21 in continual loopback mode, for the purpose of performing a
BER test, move DIP switch S1-4 to the “ON” position (see Section 3.1).
5.2 LED STATUS INDICATORS
B. Verify that the data terminal equipment is operating properly
and can be used for a test. If a fault is indicated, call a technician or
replace the unit.
The Model 2703-X21 features four front panel LEDs that indicate
the status of power, network connection, master clock and loopback
test. Figure 7 (below) shows the front panel location of each LED.
Following Figure 7 is a description of each LED’s function.
C. Perform a BER (bit error rate) test on each unit. If the BER test
equipment indicates no faults, but the data terminal indicates a fault,
follow the manufacturer’s checkout procedures for the data terminal.
Also, check the interface cable between the terminal and the Model
2703-X21.
Model 2703 MegaLink-1 G.703/E1 Modem/Converter 2.048 Mbps
Test Modes
Loop
Loopback
Normal
Figure 7. Model 2703 Front Panel
Power -
Glows red when the Model 2703-X21 is
powered up.
Network -
Glows green when the Model 2703-X21 is receiving
correctly encoded data from the line interface
equipment.
Master Clock-
Loop -
Glows green when the Model 2703-X21 is
configured as the master clock unit.
Glows green when the Model 2703-X21 is in
loopback mode.
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APPENDIX A
APPENDIX B
MODEL 2703-X21 PIN CONFIGURATIONS
PATTON MODEL 2703 SPECIFICATIONS
CCITT X.21 INTERFACE (DB-15)
Network Interface:
G.703
Network Rate:
2.048 Mbps
Network Connectors:
Two BNC (75 Ohm) and one
modular RJ-45 connector (120
Ohm)
1- Frame Ground
2- Transmit - A
3- Control - A
4- Receive - A
Transmit - B - 9
Control - B -10
Terminal Interface:
Terminal Rate:
X.21 on female DB-15 connector
2.048 Mbps, 1.024 Mbps, 512 kbps
or 256 kbps
Receive - B -11
Indication - B -12
5- In ic io
d
a
t
n
-
A
Signal Timing -B 13
6- Signal Timing - A
Diagnostics:
Indicators:
Loopback Test
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5
LEDs for power, network, master
clock and loopback test
Internal (Master) or Network
Recovered (Slave) clock
-10 dB (0dB = 2.4V)
85/265 VAC (switch selectable),
50/60 Hz; 85-265 VAC, 50/60 Hz
(universal input option); 48 VDC
(option)
8- Signal Ground
Clocking:
Receiver Sensitivity:
Power:
Temperature Range:
Altitude:
Humidity:
0-50°C (32-122°F)
0-15,000 feet
5 to 95% noncondensing
7.3” x 6.6” x 1.62” (185mm x
168mm x 41mm)
Dimensions:
Weight:
2.02 lbs.
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APPENDIX C
FACTORY PARTS AND ACCESSORIES
APPENDIX D
SAFETY WARNINGS AND REQUIREMENTS
C-1 Basic Standalone Units
These warning notices apply to the Input Port, the port marked
“Network”.
The Patton Model 2703-X21 standalone digital modem is available
in three versions, depending upon the power supply installed. The
Standard and Universal Interface versions are supplied with a power
cord, which must be specified in the model number when ordering. The
DC version is supplied without power cord.
Warning: The port marked “SAFETY WARNING: see instructions
for use” does not provide isolation sufficient to satisfy the requirements
of BS6301; apparatus connected directly to this port should either have
been approved to BS6301 or have previously been evaluated against
British Telecommunications plc (Post Office) Technical Guides 2 or 26
and given permission to attach. Any other usage will invalidate the
approval of the Interface Module.
All versions of the Model 2703-X21 are supplied without a terminal
(DTE) interface cable. This cable may be ordered separately, or may
be supplied by the user.
Interconnection of the Interface Module (the port marked
“Network”) directly, or by way of any other apparatus, with ports on
other apparatus (marked or not so marked) may produce hazardous
conditions on the network. Users should seek advice from a competent
engineer before such a connection is made.
Standard power supply option,
switchable between 115 and 230 VAC ......................Model 2703-X21/*
Universal Interface power supply option,
operates in environments ranging from
85 to 265 VAC.......................................................Model 2703-X21-UI/*
The Interface Module is approved as a Host Independent Appliqué.
As such the Interface Module is only approved for use with a host, and
with host attachments, that are either type approved in their own right,
or, if supplied after March, 1989, are covered by terms of the General
Approval number NS/G/1234/J/100003. A Host supplied under the
terms of the General Approval number NS/G/1234/J/100003 satisfies
the conditions of the paragraph above.
DC power supply option,
operates in 48 VDC environments,
equipped with a 3-pin “terminal strip”
for DC power connection.......................................Model 2703-X21-DC
C-2 AC Power Cords
The Interface Module must not be modified in any way. Any form
of modification invalidates the approval for connection, and the Patton
warranty of the unit.
Power cord must be specified when ordering Models 2703-X21 or
2703-X21-UI. If power cord is omitted, suffix “K” will be assigned.
Ordering Suffix (*)
Power Cord Description
The terms of the approval require that there must be a minimum
distance (5mm) between the Interface Module and any other part of the
host, including other Interface Modules. This condition is met by default
when the Appliquè is installed in a Patton enclosure in accordance with
the instructions. If voltages greater than 250V are present in the host ,
users should refer to a competent safety engineer for advice.
A.....................................Continental Europe, CEE 7
C.....................................Australia, New Zealand
D.....................................United Kingdom
E.....................................Denmark
F .....................................France/Belgium
G.....................................India
H.....................................Israel
I ......................................Italy
J......................................Japan
K.....................................North America
L .....................................Switzerland
It is a condition of the approval that a copy of these user
instructions and safety warnings must be supplied with the host.
Failure to provide the Interface Module user instructions with the host
will invalidate the Appliquè approval.
Failure to install the Interface Module in accordance with these
instructions will invalidate the approval. If you experience difficulties, or
are in any doubt, please contact your Patton representative.
Example: 2703-X21-UI/D = Universal Interface w/ UK power cord.
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