Modems FAQ

From dataTaker Wiki (FAQ)

PSTN, GSM, CDMA, Satellite and other Modems Frequently Asked Questions

Contents

New product range

dataTaker now have the DT8xM range of modems available. With the modem tightly integrated into the logger the is capable of simply sending SMS messages, FTP email and much more.

dataTaker Modem Products

* SMSX Modem FAQ - This page contains frequently asked questions specific to the dataTaker SMSX GSM/GPRS modem. SmsX.gif
* 905U-D Radio Modem FAQ - This page contains frequently asked questions specific to the dataTaker 905U-D radio modem. Radio mod.gif
* 905U-E Wireless Ethernet Modem FAQ - This page contains frequently asked questions specific to the dataTaker 905U-E wireless ethernet modem. Wireless ethernet.gif

Details of other modems that may be suitable for use with dataTaker products can be found on the 3rd Party Products page.

Tested Modems

* Maxon ModMax FAQ - This page contains frequently asked questions specific to the Maxon ModMax Industrial Serial Modem.
Gallery modmax.jpg
* Wavecom Fastrack Supreme FAQ - This page contains frequently asked questions specific to the Wavecom Fastrack Supreme Modem.
Fastrack.jpg

Details of other modems that may be suitable for use with Datataker products can be found on the 3rd Party Products page.

Preparation and initialisation of modems, loggers and host software

How do I configure a modem (PSTN/GSM/CDMA/Satellite/Radio/Other) to use with my DT80/800 logger?

IMPORTANT Datataker recommends using this information in preference to the information in the 800 users manual (UM-0068-A2). The DT80 user's manual has been recently updated to include similar information to that provided here.

For "bullet proof" communications we recommend that you fully preconfigure the modem and write the configuration to the modems non-volatile memory. This ensures that whenever the modem resets due to power loss or other reason it will start with the correct configuration. Refer to your modem's user's manual for information on how to go about pre-configuring the modem. This is usually done by connecting the modem to a PC and running a terminal program so that you can then send "AT" commands to configure the modem. For example, the command to configure the required DSR/CD mode then write the settings to the modem's memory might be something like:

AT&S0&C1&W

Note that the &W (write to stored profile to non-volatile memory) is required, otherwise the modem will forget the settings if it is powered off or reset. You should also set the loggers modem initialisation string to "AT" as the logger does not need to initialise the modem if it is fully preconfigured. For example

PROFILE"HOST_MODEM","INIT"="AT"

The following is a list of items that should be set in the modems configuration profile. You should check your modem users manual to determine the exact command to use for each setting.

  • Factory defaults: You may want to set the modem to factory defaults (usually AT&F command) so that you have a known starting point. Factory defaults is a good place to start if you are uncertain of which settings to use, particularly if someone has used the modem before and you are uncertain of the settings used. It is usually safer to send this command to the modem first and by itself (e.g. AT&F) as this command will reset all other settings back the factory default value. You can then set all other settings as detailed below and as required for your specific application.

There are two important hardware signals from the modem (DSR and CD); the modem must be set up such that these signals operate as follows, regardless or whether or not you preconfigure the modem as recommended here:

  • DSR always on: The DSR (data set ready) signal from the modem must be active while the modem is turned on, as this is how the logger determines that a modem is connected. Most modems do this by default, if not then you must pre-configure the modem (most modems support the command AT&S0 to do this). If the modem cannot be configured to operate in this way then the logger must be tricked by connecting DSR to DTR at the logger side, but this should be done as a last resort as it is not as robust a method. It is important for the logger to know that a modem is connected so that it can send the modem initialistion string when required, as well as to avoid sending normal data output to the modem when the modem is in command mode.
  • CD follows carrier state: The CD (carrier detect, sometimes known as DCD - data carrier detect) signal must be set to follow the carrier state, as this is how the logger determines when a connection has been established with another modem. Most modems do this by default, if not then you must pre-configure the modem to do this (most modems support the command AT&C1 to do this). If the modem cannot do this (ie. it leaves CD active all the time) then you cannot use the modem initialisation string in the logger as it will never be sent.
  • Hardware flow control: We recommend that you always use hardware flow control on the modem and the logger. For most modems this is the default. On many PSTN modems this is set using the AT&K3 command.
  • Force reliable (error correcting protocol) mode: You should ensure that the modem connection always uses an error correcting protocol such as LAPM or MNP. This is required to ensure the flow control information is passed between the logger and PC based application as well as to eliminate line errors that may corrupt the data transmission. If an error correcting protocol is not used then line errors and flow control problems can cause data loss. Many modems will fall back to a non error correcting mode if an error correcting protocol cannot be agreed with the other modem. This should be avoided as it can cause data loss. Many PSTN modems can be set to force reliable mode using the AT\N2 command. That is, they will not connect at all if an error correcting protocol is unavailable.
  • Auto answer: The DT80/800 series of loggers do not issue any commands to the modem to answer a call. Therefore, if dial-in functionality is required, the modem must be set to auto-answer incoming calls. For most modems the command ATS0=4 will set the modem to auto-answer incoming calls after 4 rings. This setting may be omitted if you do not need dial-in functionality, in which case the modem will ignore incoming calls.
  • Don’t echo commands: Most modems will echo incomming commands. This is not desirable when used with a DT80/800 series logger as the echo will be treated as a command by the logger which will only confuse it. For most modems the command ATE0 will turn off echo of modem commands.
  • Quiet mode: Most modems will issue messages whenever a command is sent to the modem or a connection is made or dropped. This is not desirable when used with a DT80/800 series logger as the messages will be treated as a command by the logger which will only confuse it. For most modems the command ATQ1 will disable the output of such messages.
  • DTR hangup: Whenever the logger wants to hang up a connection it will set the DTR signal to inactive. The modem should be set such that it will drop the connection whenever it sees DTR inactive. This behaviour can be set for most modems with the command AT&D2.
  • Fixed local baud rate. Most modems will automatically set there local baud rate ("autobaud") to the same baud rate as the local device after it sees an AT command from the device. Some modems, such as some GSM/CDMA modems, will only autobaud to a particular maximum rate (such as 19200). To use rates above this you must fix the rate using a command to the modem. To ensure more reliable communications with the modem under all conditions we recommend that you fix the rate in the modem to the same rate that you wish to use with the logger. The way to control this varies considerably across modems. For example on some modems the command AT#BDR can be used to fix the local baud rate. If the baud rate cannot be fixed then you should set the loggers baud rate to the same rate as the default rate for the modem. The only other alternative is to use the loggers modem initialiation string to send an AT command and thus set the modems local baud rate using the autobauding feature.
  • Application specific settings. You may need to set other settings in the modem that are particular to your application.

What initialisation commands should I send to a specific modem?

The follow sections show typical initialiation commands to send to different types of modems to prepare them for use with a logger.

PSTN modems

The following initialisation commands are suitable for modems that use a Rockwell chipset. It may be suitable for other types as well. Please check the modems users manual to confirm that it supports all the AT commands specified here before using these commands.

&F Sets the modem back to factory defaults. Ensures a standard starting position before setting the following options.
E0Q1&D2S0=4&C1&S0 Standard default init commands required by the logger - no echo, Quiet Mode, Hangup on DTR inactive, Auto answer after 4 rings, Carrier Detect follows line state, DSR always on.
\N2 Selects reliable (error correction mode). Forces LAPM or MNP error correction to be used, else will not connect.
 %C2 Selects data compression to be used.
&K3 Selects hardware flow control (RTS/CTS).
&W Write the current settings to non-volatile memory, so that the modem will always use these settings after a power loss.

Use the following command sequence to initialise a PSTN modem when using DeTransfer directly connected to the modem.

AT&F
ATE0Q1&D2S0=4&C1&S0\\N2%C2&K3
AT&W

To verify that the settngs have been set correctly, power cycle the modem and then send the AT&V command to output the current settings and check that the initialisation commands above have been set for the active profile.

Maxon MM-5100 CDMA modem

The following initialisation commands are suitable for Maxon-5100 modems. It may be suitable for other CDMA types as well. Please check the modems users manual to confirm that it supports all the AT commands specified here.

&F0 Sets the modem back to factory defaults. Ensures a standard starting position before setting the following options. Note: factory default setting for flow control is hardware (CTS/RTS), factory default for data compression is ON.
E0Q1&D2S0=4&C1&S0 Standard default init commands required by the logger - no echo, Quiet Mode, Hangup on DTR inactive, Auto answer after 4 rings, Carrier Detect follows line state, DSR always on.
+IPR=57600 Forces modem to use 57600 baud as local comms rate. Required as cannot autobaud above 19200. Set this baud actually want to use with the logger. 57600 is default rate for DT80 and DT800.
+ES=3,2,4 Selects reliable (error correction mode). Forces LAPM or MNP error correction to be used, else will not connect.
$QCVAD=4 Select Async for all calls. (enables data on voice number)
&W Write the current settings to non-volatile memory, so that the modem will always use these settings after a power loss.

Use the following command sequence to initialise a PSTN modem when using DeTransfer directly connected to the modem.

AT&F0
ATE0Q1&D2S0=4&C1&S0+IPR=57600;+ES=3,2,4;$QCVAD=4
AT&W

To verify that the settngs have been set correctly, power cycle the modem and then send the AT&V command to output the current settings and check that the initialisation commands above have been set for the active profile.


IG6000 Modem (DT500)

AT&F0 Factory Defaults
ATB0 Auto Connect
R9 9,600 bps (locked terminal speed - no autobaud)
AT&D0 (DTR function mode 0)
AT#MEM0 All voice features off
AT&K4 Xon/Xoff flow control
ATS0=1 Answer after 0 sec
ATE0 Local command state echo off
ATQ1 Modem does not return response codes
AT&Y0 Select stored profile n for Power on and &D3
AT&W0 Save current configuration into stored profile n (n=0,1,2,3)
ATZ0 Restore configuration profile n (n=0,1,2,3)
AT&V View active configuration profile


Use the following command sequence to initialise a PSTN modem when using DeTransfer directly connected to the modem.

AT&F0	
ATB0R9&D0#MEM0&K4S0=1E0Q1&Y0&W0Z0	
AT&V

To verify that the settngs have been set correctly, power cycle the modem and then send the AT&V command to output the current settings and check that the initialisation commands above have been set for the active profile.


IG6000 Modem (DT80)

AT&F0 Factory Defaults
ATB0 Auto Connect
R57 57,600 bps (locked terminal speed - no autobaud)
AT&D2 (DTR function mode 2)
AT#MEM0 All voice features off
AT&K3 RTS/CTS flow control
ATS0=1 Answer after 0 sec
ATE0 Local command state echo off
ATQ1 Modem does not return response codes
AT&Y0 Select stored profile n for Power on and &D3
AT&W0 Save current configuration into stored profile n (n=0,1,2,3)
ATZ0 Restore configuration profile n (n=0,1,2,3)
AT&V View active configuration profile


Use the following command sequence to initialise a PSTN modem when using DeTransfer directly connected to the modem.

AT&F0	
ATB0R57&D2#MEM0&K3S0=1E0Q1&Y0&W0Z0	
AT&V

To verify that the settngs have been set correctly, power cycle the modem and then send the AT&V command to output the current settings and check that the initialisation commands above have been set for the active profile.

SMSX Modem

The SMSX modem comes pre configured. The following profile settings are required for correct operation The profile can either be configured in the logger via DeLogger or DeTransfer.. The Following are the DeLogger commands Make sure you are connected to the appropriate logger.

  • Click DataTaker>Profile
  • Select the Host Port Tab
  • Set the data rate to 9600
  • Set the data bits to 8
  • Set the stop bits to 1
  • Set the parity to None
  • Set flow to HARDWARE
  • Select the Host Modem Tab
  • Clear Dial
  • Clear Init
  • Click OK

In Detransfer type

PROFILE"HOST_MODEM","DIAL"=""
PROFILE"HOST_MODEM","INIT"=""
PROFILE"HOST_PORT","BPS"="9600"
PROFILE"HOST_PORT","FLOW"="HARDWARE"
PROFILE"HOST_PORT","DATA_BITS"="8"
PROFILE"HOST_PORT","STOP_BITS"="1"
PROFILE"HOST_PORT","PARITY"="NONE"
SINGLEPUSH

Intercel SAM10E GSM modem

Here is a command sequence used successfully for the SAM10E GSM modem with the DT80.

AT&F
AT&S0&C1
AT+IFC=2,2
AT+IPR=57600
AT+WRST=1,"024:00"
ATS0=4
AT&D2
ATE0
ATQ1
AT&W

Using the AT&V command to verify settings gives the following response:

Q:1 V:1 S0:004 S2:043 S3:013 S4:010 S5:008
+CR:0 +CRC:0 +CMEE:0 +CBST:0,0,1
+SPEAKER:0 +ECHO:0,1 &C:1 &D:2 %C:0
+IPR:57600 +ICF:3,4 +IFC:2,2

Do I need to change the default modem initialisation string?

We recommend that you change the default initialisation string to simply "AT" as described above in preparing your modem for use. This will ensure that the modem autobauds to the current baud rate if necessary. For example:

PROFILE"HOST_MODEM","INIT"="AT"

Do I need to change DeLoad default settings when using modem connections?

You should change the connection timeout to 2 minutes when using modems. This allows time for modems to retrain during a connection, without DeLoad timing out and forcing the connection to be dropped.

Troubleshooting communications problems

Why am I having problems getting reliable data with a modem connection?

When used with DT80 and DT800 series dataTaker data loggers, modems connections require the following:

Flow Control

There are four devices involved in a modem connection: a dataTaker data logger, a Computer and two modems. We recommend that all four devices be set to hardware flow control. You must ensure an error correcting protocol is used so that the flow control state can pass from one end to another.

IMPORTANT: The default setting for DT80/800 data loggers is software flow control, you must set it hardware using the profile "HOST_PORT","FLOW_CONTROL"="HARDWARE".

WARNING The profile setting required for "HOST_PORT", "FLOW_CONTROL" is "HARDWARE" and not "HWFC" as used in the PH command. If the setting for FLOW_CONTROL is invalid, such as HWFC, then the logger will silently ignore this setting and use the default SOFTWARE flow control! Another mistake that can be made when setting the profile is to misspell the name of the section or the parameter. In this case the logger will simply setup a new profile parameter with your spelling, leaving the parameter you wanted to change untouched! Also remember that profile settings are not used until after a reset (via SINGLEPUSH or power cycle). To check what the current flow control setting actually is use the PH command.

In addition to setting the correct flow control in each device you must also ensure that an error correcting protocol is used between the modems so that flow control state is passed between the modems as well. Some modems may fall back to a non error correcting protocol connection if they cannot agree upon an error correcting protocol, during the arbitration with the other modem. If this happens then data loss can occur due to flow control mismatch. On some modems you can force an error correction protocol to be used by adding "\N2" or "+ES=3,2,4" to the modem init string.

IMPORTANT: The DT80/800 does not automatically set the modem to factory default when initialising it. Most modems factory defaults include hardware flow control. If someone has set the modem to software flow control and you have the DT80/800 set to hardware flow control then data will be lost. You can force hardware flow control on some modems by sending the modem the AT&K3 command.

IMPORTANT: When using DT5/6xx series with Modems (particularly radio modems) you may need to change P26, XOFF timeout, as the flow control may be active for quite some time. I have seen with radio modems using 2 repeaters the flow control can be active for longer than 30 seconds. The modems don't like receiving data when they have told the logger not to send anything (XOFF).

Error correcting protocol

An error correcting protocol such as LAPM or MNP is required to operate between the two modem not only to ensure proper operation of flow control between the logger and the PC but also to ensure the transmissions are error free as there is usually no specific protocol operating between the logger and PC.

Automatic baud rate selection

Most modems will change the local baud rate to match the loggers baud rate. This occurs when the logger sends the initialisation string as defined in the "HOST_MODEM","INIT" profile string. Therefore you would set the desired baud rate in the logger and the modem will simply autobaud to match.

Some modems have a maximum rate to which they will auto-baud select to. For example Maxxon CDMA modems will only select to a maximum baud rate of 19200. To use higher rates you must set the modem manually.

Cables required

You must also ensure that cables with all of the required signals are used. The required signals are GND, RX, TX, RTS, CTS, CD, DSR, DTR. A standard straight through cable with the lines connected is suitable.

Here is a more detailed explaination about the required signals.

  • GND (sometimes known as SG) should always be connected between the logger and the modem to ensure a proper reference point for both modem and logger.
  • RX, TX (sometimes known as RXD, TXD) are the lines that transmit and receive the data and MUST be connected between the logger and the modem.
  • RTS, CTS are the hardware handshaking signals and MUST be connected between the logger and the modem if using hardware flow control. We always recommend that you use hardware handshaking.
  • CD (sometimes known as DCD) is used by the logger to determine when a link to the host system has been established. This signal MUST be connected, otherwise the logger cannot tell when a link has been established.
  • DSR is used by the logger to determine that a modem has been attached. The DSR input of the logger should be connected to the DSR output of the modem. If the modem does not have DSR output you can link DSR to DTR on the logger side.
  • DTR is used by the logger to signal the modem when to hangup a connection. The DTR output of the logger MUST be connected to the DTR input of the modem.
  • RI is not used and is not required. There is no harm if the signal is connected between the logger and the modem as it will be ignored.

The following cable descriptions show the connections required for both a 9Pin to 9Pin cable and a 9Pin to 25Pin cable as well as the sex of the connector on the cable. The cable descriptions also indicate the direction of the signal (output to input).

  Logger           Modem             Logger           Modem 
 (DE9 Female)     (DE9 Male)        (DE9 Female)     (DB25 Male)
  1 CD  <---------- CD  1            1 CD  <---------- CD  8
  2 RX  <---------- RX  2            2 RX  <---------- RX  3
  3 TX  ----------> TX  3            3 TX  ----------> TX  2
  4 DTR ----------> DTR 4            4 DTR ----------> DTR 20
  5 GND ----------- GND 5            5 GND ----------- GND 7
  6 DSR <---------- DSR 6            6 DSR <---------- DSR 6
  7 RTS ----------> RTS 7            7 RTS ----------> RTS 4
  8 CTS <---------- CTS 8            8 CTS <---------- CTS 5
  9 RI  <---------- RI  9            9 RI  <---------- RI  22

See the DT80 or DT800 users manual for more information.

Changing Profile settings

To send a '\' character to the modem in the init string you need to put two '\' characters in the string as the profile string handling will treat a single '\' character as an attempt to specify a special (eg non printing) character. If you are using DeTransfer then you will need to put four '\' characters as DeTransfer also escapes these characters!

Serial Ports

We have found that some "real" serial ports do not behave properly. They can loose data and/or lock up. It appears that some real serial ports on newer computers are not implemented and/or tested properly. When used with an error correcting protocol in the application, like TCP/IP (PPP), the problems of data loss are masked by the protocol.

A possible solution is to use a USB to serial adaptor. Though be careful we have found some of these that don't function well under flow control situations. We would recommend using the ones we supply (of course) because we have tested them and found them to work reliably.

Another solution is to not use RS232 communications, use either Ethernet or direct USB communications.

Internal and Soft Modems

We have found that some soft modems, both internal and USB types, do not function properly under heavy traffic loads. Avoid using these types of modems with dataTaker data loggers. Built in modems in Laptop computers are often soft modems and should be avoided.

Use the logger to control power to the modem

The DT80 and DT800 provide a facility to power cycle the modem before initialising the modem and after long periods of inactivity. This can help if the modem gets into a "locked up" state and won't communicate. Use the command

PROFILE"HOST_MODEM","EXT_POWER_SWITCH"="-1"

to use the 12V power on the DT800 or the latching relay on the DT80 to control power to the modem. See the logger's User's Manual for more details.

Note: that for DT80 in version 6.06 and earlier versions of the firmware the feature to power cycle the modem does not work.

Why doesn't the modem connected to a DT80/DT81 answer calls?

Early versions of the DT80/DT81 would not allow the modem to auto answer if the logger is in sleep mode.

Why doesn't my CDMA/GSM modem always answer calls?

There are many reasons why the modem may not answer calls:

  • Make sure that the modem is set to Auto Answer. The default modem initialisation string includes the commands to set the modem to auto answer after 4 rings. Note that there have been reports that setting the auto answer to 1 ring will cause some CDMA modems on some networks to not answer properly.
  • Some PABX systems can interfere with the connection process. It is preferable to not call modems through PABX systems.
  • Digital phone systems such as those which utilise VoIP do not support dial-up modems and cannot be used. In this case you may need to have a regular PSTN phone line installed.
  • Make sure you are using a suitable antenna for the modem and signal conditions. You dont wont the signal to be too weak or too strong! Ensure the antenna is suitable for the network being used.
  • Modems are sometimes silently logged off the network. Generally the only way to re-establish the connection is to restart the modem. This can be done by using the "EXT_POWER_SWITCH" profile setting in the DT800/80 models. Some modems also provide a way to have them self reset at defined intervals.
  • Network congestion is another possible reason that the call cannot be established. The only course of action to resolve this is to try again at another time. If you are using an automated system such as DeLoad you may be able to schedule your calls for a quiet time of day, such as early morning, or you may setup multiple scheduled tasks to try again at different times of the day.
  • You may be able to ask the network provider to log errors on your link to further determine the cause of failed connection attempts.

Why does my GSM(SMSX) modem NEVER answer calls?

A GSM modem will often have two numbers a Voice number and a data number. The modem is configured to answer all data calls either on the voice number OR the data number. Unfortunately if a voice call is received the GSM modem will not answer the call, because it has been told it has no facility to handle a voice call. When a call is made from a PSTN modem on what is normally a voice number the calll will be made as a 'voice' call which means the GSM modem will not answer because it thinks its a voice call. The solution to this is to either

  • Use a GSM modem on the PC end instead of a PSTN modem to make the call out. GSM modems when they call out are correctly registered by the telecoms provider as data calls
  • Contact the telecoms provider and have the dialing modem number correctly registered as a 'Terminating data line'
  • Have the Logger dial the PC.

How can I send SMS messages using the Enfora GSM modem

Set the logger to a Host baud rate of 9600,n,8,1,HWFC

This can be done by either connecting directly to logger and sending the following command

PH=9600,n,8,1,hwfc 

or the better method is to set the communications rate in the profile by sending the commands

PROFILE"HOST_PORT","BPS"="9600"
PROFILE"HOST_PORT","FLOW"="HARDWARE"
PROFILE"HOST_PORT","DATA_BITS"="8"
PROFILE"HOST_PORT","STOP_BITS"="1"
PROFILE"HOST_PORT","PARITY"="NONE"
  • When the logger is connected using a 'straight through' RS232 cable it will just work

The following is an example program for sending SMS messages on an alarm

begin"TempAlm"
RA5S
 1TK(=1CV)
 alarm(1CV>30){XB}
RBX
 do'at+cmgs="0409328288"^M^J' delay(w)=500
 do'Alarm Temp ?1F1 DegC'
 do'^Z'
END
  • Note the SIM card MUST be correctly configured and have the SMS service enabled for this to work!

A summary of DataTaker DT80 modem communications capability

This is an attempt to summarize different general modem types and their capabilities together with the DT80 loggers ability to exploit those capabilities.

Modem Type Function DT80 Capability
PTSN Modem Dial In using a phone number No Protocol Yes
Dial In using a phone number PPP Protocol Yes with script
Dial Out No Protocol Yes
Dial Out PPP Protocol No
Basic Mobile Modem RS232 Comms Dial In using a phone number No Protocol Yes
Dial In using a phone number PPP Protocol Yes with script
Dial Out to another Modem No Protocol Yes
Dial Out to another Modem PPP Protocol No
Connect to the internet using GPRS No
Send an SMS message Yes
Receive and act on an SMS message No
Intelligent Mobile Modem RS232 comms (SMSX) Dial In using a phone number No Protocol Yes
Dial In using a phone number PPP Protocol Yes with script
Dial Out No Protocol Yes
Dial Out PPP Protocol No
Connect to the internet using GPRS Dependant on modem capability and requires Telnet and Server support
Connect via a Telnet connection to a IP:Port address (RS232) Yes SMSX modem needs the appropriate configuration
Send an SMS message Yes
Receive and act on an SMS message Yes
Intelligent Mobile Modem TCP/IP & RS232 Comms Dial In using a phone number No Protocol Yes
Dial In using a phone number PPP Protocol Yes with script
Dial Out No Protocol Yes
Dial Out PPP Protocol No
Connect to the Internet using GPRS (RS232) No
Connect to the Internet using GPRS (TCPIP) Yes Fixed IP address Only
Connect via a Telnet connection to a IP:Port address (RS232) No
Send an SMS message Yes
Receive and act on an SMS message No
ADSL Internet Modem Connect to the Internet (Fixed IP) Yes
Connect to the Internet (DHCP) No
ADSL Internet Modem (Incuding Router) Connect to the Internet (Fixed IP) Yes
Connect to the Internet (DHCP) Yes
Radio Modems Transparent RS232 Cable replacement connection No Protocol Yes
Cable replacement connection PPP Protocol Yes
Radio Modems Ethernet Standard IP network connection Yes Fixed IP address Only

Definitions of Terms Commonly used in Modems

Circuit Switched Data (CSD)

CSD uses a dedicated link that is agreed on, before transmitting data. This link is exclusive to the transmission of the data and released only when the session is terminated. When you use CSD over a mobile phone network, you are limited to a transmission rate of 9600 bits per second, which is relatively slow. For example, if you wish to transfer a large file such as the latest firmware (12MB+) using CSD then this could take around 3 hours.

Packet Switched Data (PSD)

With Packet Switched Data, the data is broken up into packets. Each packet may take a different path to the destination, depending on transmission loads, and other factors. At the destination this data is reassembled.

When using Packet Switched Data over a mobile phone network, you can achieve much greate transmission rates. This depends on your coverage, plan, provider and the equipment you use. Using some of the latest HSUPA modems you can achieve 7.2Mbps downlink, and 1.9Mbps uplink speeds. We would typically see rates of 4.71Mbps downlink, and 0.32Mbps uplink.

Domain Name System (DNS)

Domain Name System is a database system that translates a qualified domain name into an IP address. For example weather.datataker.com.au is easier to remember than 203.35.163.42

Dynamic DNS (DDNS)

Dynamic DNS is a service that notifies a Domain Name System name server to change the DNS configuration to reflect the change of its current IP address. This is useful when you are provided with a dynamic IP address (one that changes). For example if a modem connects to the internet with a dynamic IP it will inform the DDNS Server what this new IP address is, and in turn the DDNS server will forward any user (who typed in the DNS name) to the new IP address of the modem.

Public IP Address

A public IP address is one which is not behind a firewall and is able to be accessed by other users on the internet.

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