NAL A3LA-RS Operating and maintenance instructions

GENERAL DESCRIPTION OF MODEL A3LA-RS
Version 1.0
March 19th, 2012
TN2012-02-V1.0
Copyright © 2012 by NAL Research Corporation
9385 Discovery Boulevard, Suite 300
Manassas, Virginia 20109USA
Phone: [phone] x203
E-mail: [e-mail]

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LEGAL DISCLAIMER AND CONDITIONS OF USE
This document contains information for the Iridium A3LA-RS modem and accompanying accessories
(“Product”) is provided “as is.” Reasonable effort has been made to make the information in this document
reliable and consistent with specifications, test measurements and other information. However, NAL
Research Corporation and its affiliated companies, directors, officers, employees, agents, trustees or
consultants (“NAL Research”) assume no responsibility for any typographical, technical, content or other
inaccuracies in this document. NAL Research reserves the right in its sole discretion and without notice to
you to change Product specifications and materials and/or revise this document or withdraw it at any time.
User assumes the full risk of using the Product specifications and any other information provided.
NAL Research makes no representations, guarantees, conditions or warranties, either express or
implied, including without limitation, any implied representations, guarantees, conditions or warranties of
merchantability and fitness for a particular purpose, non-infringement, satisfactory quality, non-interference,
accuracy of informational content, or arising from a course of dealing, law, usage, or trade practice, use, or
related to the performance or nonperformance of any products, accessories, facilities or services or
information except as expressly stated in this guide and/or the Product and/or satellite service
documentation. Any other standards of performance, guarantees, conditions and warranties are hereby
expressly excluded and disclaimed to the fullest extent permitted by the law. This disclaimer and exclusion
shall apply even if the express limited warranty contained in this guide or such documentation fails of its
essential purpose.
In no event shall NAL Research be liable, whether in contract or tort or any other legal theory, including
without limitation strict liability, gross negligence or negligence, for any damages in excess of the purchase
price of the Product, including any direct, indirect, incidental, special or consequential damages of any kind,
or loss of revenue or profits, loss of business, loss of privacy, loss of use, loss of time or inconvenience, loss
of information or data, software or applications or other financial loss caused by the Product (including
hardware, software and/or firmware) and/or the Iridium satellite services, or arising out of or in connection
with the ability or inability to use the Product (including hardware, software and/or firmware) and/or the
Iridium satellite services to the fullest extent these damages may be disclaimed by law and whether advised
of the possibilities of such damages. NAL Research is not liable for any claim made by a third party or made
by you for a third party.

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TABLE OF CONTENTS
GLOSSARY ....................................................................................................................... 4
1.0 PURPOSE .................................................................................................................... 5
2.0 SPECIFICATIONS ......................................................................................................... 5
3.0 MULTI-INTERFACE CONNECTOR .................................................................................... 7
3.1 RS232 Data Interface (Standard 9-Wire Configuration) .................................................. 7
3.2 RS232 Data Interface (3-Wire Configuration) ................................................................ 7
3.3 DC Power Input ........................................................................................................ 8
3.4 Power On/Off Control ................................................................................................ 8
3.5 Typical Power Usage Profile ........................................................................................ 9
3.6 TX_ACTIVE Line ....................................................................................................... 9
4.0 ANTENNA CONNECTOR ................................................................................................. 11
5.0 SIM CARD INTERFACE .................................................................................................. 12
6.0 CONFIGURATION SETTINGS ......................................................................................... 12
7.0 MODES OF OPERATION ................................................................................................ 13
8.0 MOUNTING RECOMMENDATIONS ................................................................................... 13
9.0 BOARD LEVEL OPTION ................................................................................................. 13
10.0 TECHNICAL SUPPORT ................................................................................................. 15
APPENDIX A: AT INTERFACE .............................................................................................. 16
APPENDIX B: S-REGISTER DEFINITIONS .............................................................................. 80
APPENDIX C: SUMMARY OF RESULT CODES ......................................................................... 85
APPENDIX D: INFORMATIVE EXAMPLES ............................................................................... 88
APPENDIX E: DESCRIPTION OF THE IRIDIUM NETWORK ........................................................ 93
APPENDIX F: STANDARD COMPLIANCE ................................................................................ 99
APPENDIX G: EXPORT COMPLIANCE INFORMATION ............................................................... 100
APPENDIX H: MECHANICAL DRAWINGS ............................................................................... 101

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GLOSSARY
BIS Bureau of Industry and Security
DAV Data After Voice
DoD EMSS DoD Enhanced Mobile Satellite Services
DTE Data Terminal Equipment
DSN Defense Switch Network
EAR Export Administration Regulations
FDMA Frequency Division Multiple Access
GPS Global Positioning System
ISU Iridium Subscriber Units (Modems, Phones, Trackers)
LBT L-Band Transceiver
NIPRNET Non-Secure Internet Protocol Router Network
NOC Network Operation Center
OFAC Office of Foreign Asset Controls
PSTN Public Switch Telephone Network
RHCP Right Hand Circular Polarization
RUDICS Router-Based Unrestricted Digital Internetworking Connectivity Solution
SBD Short Burst Data
SIM Subscriber Identity Module
SMA Sub-Miniature Version A
SMS Short Message Service
TDD Time Domain Duplex
TDMA Time Division Multiple Access
VSWR Voltage Standing Wave Ratio

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1.0 PURPOSE
This document describes the electrical and mechanical interfaces of the A3LA-RS. Model A3LA-RS is an
Iridium satellite modem comprised of a 9523 transceiver module. Similar to a standard landline modem, the
A3LA-RS can be controlled by any DTE (data terminal equipment) capable of sending standard AT
commands via a serial port. A DTE can be a desktop computer, a laptop computer, a PDA, or even a micro-
controller. With the exception of being a data-only modem, model A3LA-RS is functionally compatible with
the A3LA-X and A3LA-D. The A3LA-RS does not support voice.
Services Supported:
1. Dial-Up Data Switch
2. Direct Internet Connection (or NIPRNET Connection)
3. Direct Internet Connection using Apollo Emulator (only for DoD EMSS Gateway)
4. Short Message Service (SMS)
5. Short-Burst Data (SBD)
6. Router-Based Unrestricted Digital Internetworking Connectivity Solution (RUDICS)
NOTE: The A3LA-RS does not support voice. The equivalent modem with voice capability is
the A3LA-R.
IMPORTANT: User should not disassemble the A3LA-RS for repair or services. The
warranty is voided if the A3LA-RS is disassembled. It should be returned to NAL Research
for any services.
2.0 SPECIFICATIONS
2.1 Mechanical Specifications
Dimensions: 92 mm x 48 mm x 23 mm (3.63” x 1.88” x 0.92”)
Weight: 122 g (4.3 oz)
Multi-Interface Connector: 15-Pin Male D-Sub
Iridium Antenna: SMA Female
SIM Chip Reader: Located beneath a cover plate on top of the A3LA-RS
Cooling: Convection
Enclosure: Aluminum/EMI shielding
Figure 1. Iridium Satellite Modem A3LA-RS.
DB15 Multi-Interface Connector
SMA Antenna Connector
SIM Reader under the lid

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2.2 RF Specifications
Operating Frequency: 1616 to 1626.5 MHz
Duplexing Method: TDD
Multiplexing Method: TDMA/FDMA
Link Margin: 12 dB average
Average Power during a Transmit Slot (Max): 7W
Average Power during a Frame (Typical): 0.6W
Receiver Sensitivity at 50(Typical): –118 dBm
2.3 Electrical Specifications
Main Input Voltage Range: +3.5VDC to +5.4VDC
Average Standby Current: 60mA @ 5.0VDC
Average Data Call Current: 350mA @ 5.0VDC (peak of 2A)
NOTE: The power requirements apply to DC power measured at the A3LA-RS multi-
interface connector input. The average data call current may vary depending on the field-
of-view between the modem antenna and the Iridium satellite.
2.4 Environmental Specifications
Operating Temperature Range: –30oC to +70oC (–22oF to +158oF)
Operating Humidity Range: < 75% RH
Storage Temperature Range: –40oC to +85oC (–40oF to +185oF)
Storage Humidity Range: < 93% RH
2.5 Data I/O Specifications
Dial-Up Data/RUDICS: 2.4 Kbits/sec (average)
Direct Internet: 2.4 Kbits/sec (average)
Short-Burst Data: 1960 bytes for Mobile-Originated and 1890 bytes for Mobil-Terminated
Short Messaging: 160 Characters (maximum)
Hardware Interface: RS232
Software Interface: Standard AT Commands
2.6 Related Hardware
Antennas: SYN7391 Series, SAF2040 Series, SAF5340 Series, SAF5350 Series
Data Kit/Connector: HRC-24-11RS
Power Adapters: LA-3098, LA-7021
2.7 Reference Documents
A3LA-RS Product Information
Getting Started With Model A3LA-RS (TN2012-01-V1.0)
SatTerm Software Manual (TN2012-03-V8.5)
Additional Information on DirectIP SBD (TN2007-637-V1.0)
Additional Information on SBD (AN2012-04-V4.0)

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3.0 MULTI-INTERFACE CONNECTOR
The multi-interface connector is a male 15-pin miniature D-Sub type that includes four interfaces—
RS232, DC input power, ON/OFF control line, and TX_ACTIVE. The multi-interface connector pin
assignments are summarized in Table 1.
Table 1. Pin assignment for the multi-interface connector.
3.1 RS232 Data Interface (Standard 9-Wire Configuration)
The A3LA-RS supports a standard RS232 data interface to a DTE incorporating hardware handshaking
and flow control. The RS232 data interface comprises of eight standard RS232 data, control and status
signals plus a ground level signal reference as shown in Table 1. This interface allows a connected DTE to
utilize the A3LA-RS’s modem functionality through standard AT and extended sets of AT commands. These
commands are defined in Appendix A. The A3LA-RS will automatically adjust to the DTE baud rate and
override the +IPR setting when dissimilar. Autobaud will occur on the following characters ‘a’, ‘A’ or CR
(carriage return). Autobaud will also occur on the escape sequence character, provided this is an odd
number of characters. Normally this is set to ‘+’ in register S2 (see Appendix A for details).
Note that the Ring Indicator is used by the A3LA-RS to indicate that a Mobile Terminated SBD (MT-SBD)
message is queued at the gateway. Application developers can monitor this pin and apply appropriate AT
commands to the A3LA-RS to retrieve the MT-SBD message.
3.2 RS232 Data Interface (3-Wire Configuration)
A 3-wire RS232 data interface may also be implemented. Because of risk of over-run and data loss
especially at high baud rates, the 9-wire interface is the recommended implementation. Several steps must
be taken to allow 3-wire configuration (i.e. only using S_TX, S_RX, and SIGNAL GND). These steps ensure
the A3LA-RS and DTE to work together without having hardware handshaking.
PIN #
SIGNAL
DESCRIPTION
INTERFACE
1
EXT_B+
External 3.5VDC –6.0VDC input
DC Power
2
N/C
3
EXT_GND
External GND input
DC Power
4
EXT_ON_OFF
Power on/off control input
DC Power
5
N/C
6
S_TX
RS232 Transmit Data (Input)
RS232 Data
7
S_RX
RS232 Receive Data (Output)
RS232 Data
8
EXT_GND
External GND input
DC Power
9
DCD
RS232 Data Carrier Detect
RS232 Data
10
DSR
RS232 Data Set Ready
RS232 Data
11
CTS
RS232 Clear To Send
RS232 Data
12
RI
RS232 Ring Indicate
RS232 Data
13
RTS
RS232 Request To Send
RS232 Data
14
DTR
RS232 Data Terminal Ready
RS232 Data
15
TX_ACTIVE
Transmit Active Signal
GPIO

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1. The modem’s DTR line must be held high. Using the modem’s input voltage is fine for this purpose
BUT ONLY if the input voltage is less than 5VDC (see important note below). Looping back the
modem’s DSR line to DTR line will NOT work. The DSR line on the modem should be left
unconnected.
2. Disconnect the CTS, DCD, DSR, DTR, RTS and RI lines between the DTE and modem.
3. AT&Dn must be set to AT&D0 to ignore the DTR input from the DTE.
4. AT&Kn must be set to AT&K0 for no flow control or AT&K4 for XON/XOFF software flow control.
5. The setting can be stored on the modem permanently (until another setting overwrites it) so that it
remains after a power cycle. The modem allows two profiles in which settings are stored, and user
can choose either as a default profile. The relevant commands are &Wn and &Yn. &Wn stores the
present configuration in profile <n>, where <n> can be either 0 or 1. &Yn designates which profile
is loaded after reset or power-up, again <n> is either 0 or 1.
6. Any needs of the DTE must be addressed separately.
WARNING: DO NOT use the modem’s input voltage to bring the DTR line high when the
input voltage is higher than 5VDC. Supplying voltage higher than 5VDC to the DTR line will
permanently damage the A3LA-RS.
NOTE: The Iridium’s Direct Internet service when using the Windows-based Apollo client
requires DCD to be present; hence it is incompatible with a 3-wire serial configuration. The
Direct Internet with Apollo client is available only on the EMSS DoD gateway and NOT on
the commercial gateway.
3.3 DC Power Input
The DC power input is through pin 1 (EXT_B+) and pins 3 & 8 (EXT_GND). Cables used to supply power
to the A3LA-RS should be kept as short as possible to prevent significant voltage drop, which can cause the
A3LA-RS to malfunction during a data call, an SMS session or an SBD session. Power reset by the A3LA-RS
during a call is an indicative of the DC power source unable to sustain voltage above 3.5VDC at peak current
demand.
3.4 Power On/Off Control
With the EXT_ON_OFF pin is left unconnected, the A3LA-RS will automatically turn on or off when
external DC power is applied or removed. Prior to turning the A3LA-RS off, command AT*P0 should be
issued to ensure all memory write activity is completed. When the A3LA-RS is powered off, its internal
power-on-reset circuit requires two seconds for voltages to decay. Users should not re-apply power until this
time has elapsed. If the two-second wait time is not adhered to, the reset circuit may not operate and the
A3LA-RS could be placed in a non-operational state. The state is not permanent and can be rectified by the
above procedure.
The EXT_ON_OFF pin can be connected to an external I/O control line to turn a powered A3LA-RS on
and off in a toggle fashion. With this setup, the EXT_ON_OFF line MUST first be held to GND level (i.e. logic
low) before applying power to the A3LA-RS. As long as DC power input is applied, logic high on the

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EXT_ON_OFF line turns the A3LA-RS on and a logic low turns it off. Logic high is defined as having a voltage
ranging from 2.0V to 5.5V—do not allow logic high to exceed 6V. Logic low can range from 0.3V to 0.8V.
The current drawn on the external load used to pull the A3LA-RS to GND is no more than 20A. The A3LA-
RS will draw approximately 20mA even in off state. Thus, DC power must be removed to eliminate any
parasitic current drawn. Damage may be caused to the A3LA-RS if EXT_ON_OFF is high and DC power is not
present. Users must ensure that this condition does not occur.
3.5 Typical Power Usage Profile
This section provides the electrical power profile of the A3LA-RS. It does not describe every situation;
however, it does offer a starting point for users to continue their own development design. The actual usage
profile can vary for a number of reasons. Users are reminded to optimize their setup to attain the lowest
possible power consumption. Some of the setup parameters to be carefully observed include:
1. Have a clear view of the sky for the antenna—poor visibility of the sky is when a clear line-of-sight
is not available between the A3LA-RS and the satellites.
2. Keep the antenna’s VSWR low—the higher the antenna VSWR the higher the current consumed by
the A3LA-RS.
3. Keep the antenna cables’ loss to less than 3dB—the higher the antenna cable loss the higher the
current consumed by the A3LA-RS.
4. Keep the power cable between the A3LA-RS and the power source as short as possible.
Power consumption of the A3LA-RS can be divided into four distinct operating segments: (1) standby,
(2) data-switch/RUDICS call, (3) SBD transmission, and (4) SMS transmission. Typical current drawn for
these cases are shown in plots below.
3.0 3.5 4.0 4.5 5.0 5.5 6.0
Voltage (DC)
0.00
0.05
0.10
0.15
0.20
Current (A)
Figure 2. Average current drawn during standby.

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3.0 3.5 4.0 4.5 5.0 5.5 6.0
Voltage (DC)
0.00
0.15
0.30
0.45
0.60
Current (A)
Figure 3. Average current drawn during a data switch call.
3.0 3.5 4.0 4.5 5.0 5.5 6.0
Voltage (DC)
0.00
0.15
0.30
0.45
0.60
Current (A)
Figure 4. Average current drawn during an SBD transmission.

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3.6 TX_ACTIVE Line
If the A3LA-RS is used near a GPS receiver, it is possible that the input circuitry of the GPS receiver
could be damaged by the output power of the Iridium transmitter, especially if the two devices share a
single antenna. The TX_ACTIVE signal can be used to monitor when the A3LA-RS is in transmitting mode
allowing a nearby GPS receiver to be turned off. The TX_ACTIVE signal goes high 610 sec before the start
of a transmission burst (i.e. full power), and goes low 220 sec after the end of the burst. There is also 100
sec of power ramp-up before the burst and 100 sec of ramp-down after the burst.
4.0 ANTENNA CONNECTOR
The A3LA-RS modem uses a single SMA female 50-ohm connector for both transmit and receive. Cable
loss between the modem and the antenna is critical and must be kept less than 3dB at the operating
frequency of 1616 to 1626.5 MHz. The minimum link margin of 13.1 dB must also be maintained. General
RF parameters are listed in the table below.
NAL Research offers several types of antennas for use with the A3LA-RS modem. These antennas
include the fixed mast, mobile magnetic/permanent mount and portable auxiliary. For low-cost and
applications where small form-factor and light-weight are required, NAL Research recommends model
TYPE
DESCRIPTION
Frequency Range
1616 to 1626.5 MHz
Input/Output Impedance
50 Ohms
Oscillator Stability
1.5ppm
3.0 3.5 4.0 4.5 5.0 5.5 6.0
Voltage (DC)
0.00
0.15
0.30
0.45
0.60
Current (A)
Figure 5. Average current drawn during an SMS transmission.

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SYN7391-C. If the specific application requires a custom antenna, it must meet the specifications in the
following table.
Satellite signal strength reported by the A3LA-RS when issuing an AT+CSQ command indicates the
signal strength of the ring channel. Care should be taken when using this signal reading for comparisons
between devices. Of particular notes are the followings:
1. There is a 0.5 dB tolerance on the calibration.
2. Each bar represents a 2 dB increment.
3. Multiple ring channels can be present at the same time so units can lock to different signals.
4. If the reading is near the decision threshold it would be easy to see a 1 bar difference.
5.0 SIM CARD INTERFACE
The A3LA-RS modem contains an integrated SIM reader. The modem uses and requires an Iridium SIM
chip for operation. The SIM chip is detached from the full-size Iridium SIM card. The SIM chip is inserted
into the opening located on top of the modem. A plastic locking mechanism (same as with GSM wireless
phones) is used hold the SIM in-place. Place the SIM chip (facing down) into the SIM reader’s bracket as
shown in Figure 6. Make sure that the cut-off on the SIM chip aligns with the SIM reader.
6.0 CONFIGURATION SETTINGS
The A3LA-RS allows users to configure its data port communication parameters. The three configuration
types are active, factory default, and stored. The active configuration is the set of parameters currently in
PARAMETER
VALUE
Operating Temperature Range
–40oC/+85oC without loss of function
Measurement Frequency Range
1616 to 1626.5 MHz
VSWR
< 1.5 : 1
Maximum Gain
3 dBic
Nominal Impedance
50 Ohms
Polarization
Right Hand Circular (RHCP)
Basic Pattern
Omni directional and hemispherical
Figure 6. Location of the SIM reader.
SIM Chip
SIM Reader

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use. They can be changed by the users individually via specific AT commands. The factory default
configuration is stored in permanent memory. This configuration can be recalled at any time through use of
the AT&Fn command.
Two groups of settings, or “profiles”, can be stored as user-defined configurations. Users first create
desired active configurations and then write them to memory using the AT&Wn command. These profiles can
be designated to be loaded as the active configuration upon A3LA-RS power-up through use of the AT&Yn
command. The A3LA-RS can be reset without loss of power to these profiles through use of the ATZn
command. The configuration settings are stored in “S-register” locations and are detailed in Appendix A.
7.0 MODES OF OPERATION
The A3LA-RS serial data port is always in one of three modes: command mode, SBD data mode or SBD
session mode. When the data port is in command mode, AT commands can be entered to control the A3LA-
RS. In command mode, flow control has no effect, with the RTS input ignored and the CTS output driven ON
(low). When in SBD data mode, the A3LA-RS is transferring binary or text SBD message data to or from the
DTE. In SBD data mode:
1. All characters from the DTE not forming part of the message data are ignored (i.e. no AT commands
may be entered).
2. No unsolicited result codes are issued.
3. RTS/CTS flow control, if enabled, is active. When RTS is OFF (high), the A3LA-RS suspends transfer
of data to the DTE; when CTS is OFF (high), the A3LA-RS expects the DTE to suspend transfer of
data.
When in SBD session mode, the A3LA-RS is attempting to conduct an SBD session with the network. In
SBD session mode:
1. The DTE must wait for the +SBDI [X][A] session result code.
2. All characters from the DTE are ignored.
3. Unsolicited result codes are issued where those codes have been enabled.
Transitions between the modes of operation are performed automatically by the A3LA-RS in response to
the SBD AT commands; the DTE has no other control over the mode.
8.0 MOUNTING RECOMMENDATIONS
The A3LA-RS has four features on its bottom surface that can aid in its mounting (see Appendix H).
These four features are pre-drilled at a minimum depth of 0.25 inch to accept 2-56 thread type.
9.0 BOARD LEVEL OPTION (A3LA-RSP)
NAL Research also offers the A3LA-RS without the housing for application developers who wish to
integrate the modem boards directly into their products. The exploded view of the A3LA-RS is shown in
Figure 7. Part number for the board-level is A3LA-RSP. NAL Research ships the A3LA-RSP with the following
items included –item 6 (RF board mounting screws), item 9 (antenna cable), item 10 (antenna washer),
item 11 (antenna nut), item 12 (Iridium 9523 RF board), item 13 (NAL Research SIM reader circuit and PA
boost circuit), and DB15 connector (not soldered on the board).

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Figure 7. Exploded view of the A3LA-RS.
ITEM DESCRIPTIOM
1 A3LA-RS case
2 A3LA-RS lid
3 A3LA-RS SIM lid
4 1/8” 2-56 flat head screw
5 1/4" 2-56 flat head screw
6 3/16” 2-56 flat head screw
7 M1.6 socket head screw 5mm
8 3/16” x 3/16” hex SS standoff
9 SMA to U.FL cable 100mm
10 SMA washer
11 SMA nut
12 9523 RF board
13 SIM/PA board
Figure 8. A3LA-RSP comprised mainly of items 12 and 13 (dimensions are in inches).

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The A3LA-RSP is shipped without the multi-interface DB15 connector mounted on the SIM/PA board.
This allows users to solder their own connector or cable directly onto the board. The 9523 RF board must
first be removed from the SIM/PA board before soldering to prevent heat from damaging the 9523. Figure 9
is a picture of the SIM/PA board without the 9523 on it. It shows the location of pin 1 of the multi-interface
connector as defined in Table 1. Pin 9 locates immediately below in 1. Users MUST choose DC power input
wires appropriately to handle high current drawn. In addition, shielded RS232 lines are recommended.
NOTE: When handling the A3LA-RP, users MUST work on ESD protected environment
including grounded work stations as well as self-grounded.
10.0 TECHNICAL SUPPORT
FOR TECHNICAL SUPPORT, PLEASE CONTACT US AT
Phone: [phone]
FAX: [phone]
E-mail: [e-mail]
Technical documents are also available to download on NAL Research’s website
www.nalresearch.com
Figure 9. Picture of the SIM/PA board without the 9523.
SIM/PA board
without the 9523
Pin 1 (square hole)
Pin 9

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APPENDIX A: AT INTERFACE
A.1 Command Types
The A3LA-RS employs two principal types of AT commands: basic and extended. The two types have
differing syntax used to query and adjust their settings. They also have unique reference standards. A
specific basic AT command is used to reference S-registers and query and adjust their settings. Its syntax is
similar to that of extended AT commands.
A.2 Basic Commands
Basic commands are industry standard and originally developed for Hayes-compatible PSTN modems. In
many cases, basic commands consist of a single ASCII alpha character. In other cases, a special character
precedes the alpha character. Prefix characters used in A3LA-RS basic commands include &, \, %, and *.
Most alpha characters in basic commands are followed by a numeric parameter, n. To adjust its setting,
a basic command is entered with the appropriate numeric value of n. Note that if the numeric parameter n is
omitted from the basic command entry, a value of zero is assumed for n. For example, ATXn is set to a
value of 4 by entering ATX4, whereas it is set to value of 0 by entering either ATX0 or ATX.
To query a basic command setting, the AT&V command is entered to view the active configuration of a
group of basic commands. Some basic commands listed in this document are marked with “No action,
compatibility only”. In these cases, the basic command is accepted in the same fashion as is with other
modems, but has no effect on the operation of the A3LA-RS, since it has no meaning in the Iridium
environment.
A.3 Extended Commands
Extended commands perform actions or set parameters that extend the capability of the A3LA-RS
beyond that which is allowed by basic commands. In some cases, they were designed for non-PSTN
networks, such as the GSM network.
Most extended commands include a prefix of + followed by a single alpha character. Prefixes used in
A3LA-RS extended commands include +C, +D, +G, +I, and +S. Extended commands designed specifically
for Iridium products include a –MS prefix. Most extended commands include three alpha characters after the
prefix, but some commands include just one or two alpha characters after the prefix.
Some extended commands have a single execution mode. No further syntax is added after the prefix
and body of the command. For example, AT+GSN is entered as shown to query the A3LA-RS for its assigned
serial number (i.e. IMEI). Some extended commands incorporate a test mode to query their range of valid
responses. Some extended commands incorporate set, read, and test modes. For example, AT–MSVTR is
entered as AT–MSVTR=n in set mode to enable/disable receipt of DTMF messages. It is entered as AT–
MSVTR? in read mode to query its current setting and is entered as AT–MSVTR=? in test mode to query its
range of valid settings. Extended commands are grouped as shown below.
Extended Cellular Commands:
+C prefix
Used for GSM cellular phone-like functions
Standards: ETSI specifications GSM 07.07 [2] and GSM 07.05 [3]
Extended Data Compression Commands:

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+D prefix
Used for data compression
Standard: V.25ter [1]
Extended Generic Commands:
+G prefix
Used for A3LA-RS issues such as identities and capabilities
Standard: V.25ter [1]
Extended Interface Control Commands:
+I prefix
Used to control the DTE interface
Standard: V.25ter [1]
Extended Short Burst Data Commands:
+S prefix
Used for Short Burst Data messaging
Iridium Satellite Product Proprietary Commands:
–MS prefix
Proprietary to the Iridium product line
A.4 Command and Response Characters
The execution of a command string follows a left-to-right execution of each command followed by the
reporting of a result code for the entire string. The ASCII character set (CCITT T.50 International Alphabet
5, American Standard Code for Information Interchange) is used for the issuance of commands and
responses. Only the low-order 7 bits of each character are used for commands or parameters; the high-
order bit is ignored. Upper case characters are equivalent to lower case characters.
A.5 Command Entry
An AT command is a string of characters sent by the DTE to the A3LA-RS while it is in command mode.
A command string has a prefix, a body, and a terminator. The prefix consists of the ASCII characters AT or
at. The body is a string of commands restricted to printable ASCII characters. The default terminator is the
<CR> character. AT command entry syntax is critical, and the following rules apply:
All commands (apart from A/ and +++) begin with a prefix of AT or at.
The commands in a command string (apart from A/ and +++) are executed only after the
return or enter key is pressed.
Use of upper or lower case letters is allowed, but not a combination of both.
The maximum number of characters in a command string is 128.
If the numeric parameter n is omitted from the basic command entry, a value of zero is
assumed for n.
If an optional parameter is omitted from an extended command, the current value is implied.
Optional parameters are enclosed by square brackets ([...]) in this document.

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Spaces entered into a command string for clarity between the AT prefix and the body of the
command are ignored. Likewise, spaces entered for clarity within the command body between
alpha characters and decimal parameters are ignored.
The backspace or delete keys can typically be used to edit commands.
Characters that precede the AT prefix are ignored.
Ctrl-x can be used to abort a command line input.
Consider the following six commands to be entered in a single command line:
ATX0 (set basic command ATXn to n=0)
AT&V (execute basic command AT&V)
AT+GSN (execute extended command AT+GSN)
AT+CMEE=? (query the valid range of responses of extended command AT+CMEE)
AT+CPBR=1,12 (execute extended command AT+CPBR with parameters 1 and 12)
AT–MSVTR? (query the current setting of extended command AT–MSVTR)
The following are valid single command line entries of above six commands:
at x 0 &v +gsn +cmee=? +cpbr=1,12 -msvtr? (all lower case)
AT X 0 &V +GSN +CMEE=? +CPBR=1,12 –MSVTR? (all upper case)
ATX 0 &V +GSN +CMEE=? +CPBR=1,12 –MSVTR? (space omitted between AT and X)
ATX0 &V +GSN +CMEE=? +CPBR=1,12 –MSVTR? (space omitted between ATX and 0)
ATX &V +GSN +CMEE=? +CPBR=1,12 –MSVTR? (0 omitted from ATX0)
ATX;&V;+GSN;+CMEE=?;+CPBR=1,12;–MSVTR? (semicolon separators)
ATX&V+GSN+CMEE=?+CPBR=1,12–MSVTR? (no separators)
A.6 Command Responses
A result code is sent to the DTE in response to the execution of a command. It may also occur
unsolicited from other conditions such as an incoming call (e.g. RING). Responses returned as a result of a
query are called information responses.
Result codes can be represented by text if the A3LA-RS is in verbose mode or with numbers if in
numeric mode. The command ATVn informs the A3LA-RS whether to respond in verbose or numeric mode.
Further note that responses can be suppressed by setting the command ATQn to ATQ1. Table below shows
the difference in format between these modes.
Numeric Mode
ATQ0 ATV0
Verbose Mode
ATQ0 ATV1
Result codes
<NUMERIC_CODE><CR>
<CR><LF><VERBOSE_CODE><CR><LF>
Information Responses
<TEXT><CR><LF>
<CR><LF><TEXT><CR><LF>

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Command entries with invalid syntax typically respond with ERROR. Command entries of valid syntax
with an out-of-range parameter can respond in one of three following manners:
Disallow out-of-range entry and respond with ERROR
Disallow out-of-range entry and respond with OK
Disallow out-of-range entry, accept the closest in-range value, and respond with OK
A.7 Hardware Failure Reporting
If the A3LA-RS detects a hardware problem during initialization, it may be unable to function correctly.
The A3LA-RS notifies the DTE of this situation by issuing an unsolicited result code at the end of
initialization:
HARDWARE FAILURE: <subsys>,<error>
where <subsys> identifies the software subsystem that detected the error, and <error> is the subsystem
specific error code. Any AT commands that cannot be handled in the failure condition will terminate with
result code 4 (“ERROR”).
A.8 Command Set Description
A.8.1 AT –Attention Code
This is the prefix for all commands except A/ and +++. When entered on its own, the A3LA-RS
will respond OK.
A.8.2 A/ –Repeat Last Command
Repeat the last command issued to the A3LA-RS unless the power was interrupted or the unit is
reset. A/ is not followed by <CR>.
A.8.3 +++ –Escape Sequence
The escape sequence is used to transfer from in-call data mode to in-call command mode
without disconnecting from the remote modem. After a pause, the A3LA-RS will respond with
OK. Register S2 can be used to alter the escape character from +, the factory default, to any
hexadecimal value in the range 0 to 255.
A.8.4 En –Echo
Echo command characters.
0Characters are not echoed to the DTE
1Characters are echoed to the DTE (default)
A.8.5 On –Online
Enter in-call data mode. This is used to return to in-call data mode from in-call command mode
using an existing connection. An error is reported if on-hook.
0 Switch from in-call command mode to in-call data mode
Any value for n accepted
A.8.6 Qn –Quiet Mode
Control A3LA-RS responses.
0A3LA-RS responses are sent to the DTE (default)

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1A3LA-RS responses are NOT sent to the DTE
A.8.7 Vn –Verbose Mode
Set the response format of the A3LA-RS, which may be either numeric or textual.
0Numeric responses
1Textual responses (default)
A.8.8 Wn –Error Correction Message Control
Set the format of the CONNECT messages.
0Upon connection, the A3LA-RS reports the DTE speed (default)
1Upon connection, the A3LA-RS reports the line speed, the error correction protocol
and the DTE speed in that order
2Upon connection, the A3LA-RS reports its data port speed
A.8.9 Zn –Soft Reset
Reset the A3LA-RS to a user-stored configuration.
0Restores user configuration 0
1Restores user configuration 1
A.8.10 &Cn –DCD Option
Select how the A3LA-RS controls the DCD behavior.
0DCD is forced on at all times
1DCD indicates the connection status (default)
A.8.11 &Dn –DTR Option
Set the A3LA-RS reaction to DTR signal.
0 DTR is ignored in all modes. A DTR signal input is not needed when set to &D0.
For all other &Dn settings, the following applies.
DTR must be ON during on-hook command mode. If DTR transitions from ON to OFF during on-
hook command mode, operation will be locked after approximately 10 seconds. On-hook
command mode operation will resume when DTR is restored ON.
DTR must be ON at call connection
DTR must be ON during both in-call command mode and in-call data mode. Reaction to DTR ON
to OFF transitions during in-call command mode and in-call data mode is determined by the
&Dn setting as shown below. Note that the +CVHU command can be set to override these
specified reactions.
1 If DTR transitions from ON to OFF during in-call command mode, and DTR is
restored ON within approximately 10 seconds, the call will remain up. If DTR is not
restored ON within approximately 10 seconds, the call will drop to on-hook
command mode.
If DTR transitions from ON to OFF during in-call data mode, the mode will change
to in-call command mode. If DTR is restored ON within approximately 10 seconds,