Modem AT Commands

Moving between command and on-line states

When the modem is turned on or after reset, the modem always goes to command state. It enters on-line state after successfully making a connection with a remote modem, either when answering or originating a call. While the modem is in on-line state, you can take control of it again (go back to command state). When you return to command state from on-line state, the modem goes to local command state, which allows you to maintain the connection and enter commands.

To go to local command state, type the escape sequence +++. Do not type any other commands or make entries before or after the escape sequence for a period equal to the guard time set in register S12 (normally one second). The modem will display OK.

To go back to on-line state, type ATO.

To hang up, type ATH.

AT command set

AT refers to the command prefix (attention sequence) that precedes each command to the modem. With the exception of A/ all commands must be preceded by AT and end with a carriage return.

Special Commands

A/    Repeat last command

The A/ command instructs the modem to repeat the last command line. A command line termination character is not required for the execution of this command (that is, the command is executed as soon as the slash is typed). This command does not use AT prefix.

+++ Return to command state (escape sequence)

The escape sequence is used to force the modem back to local command state from on-line state. Do not type any other commands or make entries before or after the escape sequence for a period equal to the guard time set in register S12 (default is one second). This command does not use AT prefix.

Standard AT commands
AT   The attention command prefix
The prefix AT must precede every command. The remainder of the command line contains commands for the modem. The command line must end with a carriage return. If AT is sent alone (that is, it is followed by a) then no command is executed but an OK result code is returned.  
A Answer
The A command forces the modem to go off-hook in answer mode.

   Bn

Communication protocol category preference

This command determines which communication standard is preferred for the next connection.

 0 -  CCITT mode V.22 at 1200 bps.
 1 -  Bell 103 and Bell 212A at 1200 bps, instead of V.21 and
       V.22, in case of fallback (default). Not supported in the UK.
 2 -  When making a call using CCITT V.23, transmit at 75 bps
       and receive at 1200 bps. When answering and N0, transmit
       at 1200 bps and receive at 75 bps.
 3 -  When making a call using V.23, transmit at 1200 bps and
       receive at 75 bps. When answering and N0 selected,
       transmit at 75 bps and receive at 1200 bps.
15 - Use CCITT V.21 at 300 bps.
16 - Use 103 at 300 bps. Not supported in the United Kingdom.
41 - Use CCITT V.32 at 4800 bps.
42 - Use Express 96 at 4800 bps.
60 - Use CCITT V.32 at 9600 bps.
61 - Use Hayes Express 96 proprietray protocol 9600 bps
       connection.
D Dial (Originate mode)
This command signals the modem that the numbers, letters, and commas that follow are all part of a telephone number that it should dial.
En Echo off/on
When the echo is turned on, the characters sent to the modem in command state are echoed back by the modem to the host computer. The E command is functional only when the modem is in command state.
0 - Turns off the echo command.
1 - Turns on the echo command. This allows you to see that characters you have sent to the modem have been received and sent back. (default)
Hn Hook (hang up)
When the modem is on-line, you must first enter the +++ escape sequence to take the modem back to command state before issuing the hang up command, ATH.
0 - Forces the modem on-hook. Hangs up the modems connection to the telephone line and place modem in command state.
1 - Forces the modem off-hook. After going off hook, operate auxilary relay.
In Information
0 - Show numeric product code.
1 - Returns calculated ROM checksum.
2 - ROM checksum is verified (output is OK or ERROR)
3 - Returns the modems country code (depends on mfg.).
4 - Returns a list of modem features (depends on mfg.).
5 - Returns country (depends on mfg.)
6 - Returns firmware version (depends on mfg.).
7 - Manufacturer defined.
8 - Manufacturer defined.
9 - Manufacturer defined. On Apple returns product code and firmware version of the modem.
   Nn

Communication protocol preference
Sets the modem protocol.
0 - Use S37 for speed selection. If S37=0, connect at highest possible speed. Otherwise, connect at speed specified in S37.

1 - Connect at speed set in S37. Fallback if necessary. (default)
Negotiate common communication standard, while originating, at the optimum line speed supported by both modems. Negotiations start at the DCE line speed specified in S37, dropping back to a slower speed if required. Go back from CCITT V.22 to CCITT V.21, when answering.

2 - Same as N1 for compatibility reasons.
(Note: For N1 or S37=0, the setting of ATB is ignored. The modem automatically determines Bell or CCITT mode.)
Negotiate common communication standard, while originating, at the optimum line speed supported by both modems. Negotiations start at the DCE line speed specified in S37, dropping back to a slower speed if required. Go back from CCITT V.22 to CCITT V.23/CCITT V.21, when answering.

3 - Handshake only at speed defined by S37, when originating. Go back from CCITT V.32 to CCITT V.22./212A/CCITT V.22bis, finally 103, when answering.

4 - Handshake only at speed defined by S37, when originating. Go back from CCITT V.32 to CCITT V.22./212A/CCITT V.22bis, finally 103, when answering.

5 - Negotiate common communication standard, while originating, at the optimum line speed supported by both modems. Negotiations start at the DCE line speed specified in S37, dropping back to a slower speed if required. Handshake only at speed defined by S37, when answering.
Ln Speaker volume
This command has no effect as the speaker is a component of the Macintosh and set in the Sound control panel.
0 - low volume
1 - low volume
2 - medium volume
3 - high volume
(Note: some modems support only on(1) and off(0) )
Mn Speaker on/off/auto
0 - Disables speaker.
1 - Turns on the speaker until carrier is detected. (default)
2 - Leaves the speaker on throughout the entire connection.
3 - Turns the speaker on until a carrier is detected, except during dialing.
On Return to on-line state
Returns modem to on-line state from command state.
0 - Is used to return to the on-line state after having entered the command state using the escape sequence.
1 - Same as above and will retrain the carrier (possibly at a lower speed) before reentering on-line state.
3 - Enter on-line state. Then start CCITT V.32bis rate renogotiation sequence. 		  Qn Quiet (refer to command Vn)
0 - Allows result codes to be sent to your screen. (default)
1 - Turns off the result code messages.
2 - Returns result codes when originating a call, but not when answering.
Sn Select an S register (see last chapter)
The S registers refer to memory locations used for configuration. The S commands are used to assign values to various registers in the modems memory.
The Sn? command (n=register number) is used for checking the contents of a register. The result is always expressed as a three-digit number, where the leading digits or all digits may be 0.
Sn=r is used to change an S register value (where n is the number of the register and r is the assigned value).		   Vn Verbalize
The V command allows you to choose the way you want to display result messages: as code numbers or as English words. Unless these messages are being read by a program that does not easily recognize strings of characters, the default setting (V1) is recommended
0 - Displays result messages as code numbers (nonverbal).
1 - Displays result messages as English words (verbal). (default)

Verbalize result codes

0 OK Command is correct and has been completed
1 CONNECT Connection established
2 RING Incoming ring detected
3 NO CARRIER No connection or lost the carrier
4 ERROR Bad command
5 CONNECT 1200 Connection established at 1200 bps
6 NO DIALTONE Dial tone not detected in S7 seconds
7 BUSY Busy tone detected 8 NO ANSWER See ATD . . .@. . .
10 CONNECT 2400 Connection established at 2400 bps
11 CONNECT 4800 Connection established at 4800 bps
12 CONNECT 9600 Connection established at 9600 bps
13 CONNECT 14400 Connection established at 14400 bps
15 CONNECT 7200 Connection established at 7200 bps
16 CONNECT 12000 Connection established at 12000 bps
24 CONNECT 300/REL Connection with MNP 300 bps
25 CONNECT 1200/REL Connection with MNP 1200 bps
26 CONNECT 2400/REL Connection with MNP 2400 bps
27 CONNECT 4800/REL Connection with MNP 4800 bps
28 CONNECT 9600/REL Connection with MNP 9600 bps
29 CONNECT 7200/REL Connection with MNP 7200 bps
30 CONNECT 12000/REL Connection with MNP 12000 bps
31 CONNECT 14400/REL Connection with MNP 14400 bps

Protocol negotiation progress codes that work with ATW1 and S95.

40 CARRIER 300 Carrier detected at 300 bps
46 CARRIER 1200 Carrier detected at 1200 bps
47 CARRIER 2400 Carrier detected at 2400 bps
48 CARRIER 4800 Carrier detected at 4800 bps
49 CARRIER 7200 Carrier detected at 7200 bps
50 CARRIER 9600 Carrier detected at 9600 bps
51 CARRIER 12000 Carrier detected at 12000 bps
52 CARRIER 14400 Carrier detected at 14400 bps
66 COMPRESSION: CLASS 5 MNP class 5
67 COMPRESSION: V.42BIS V.42 bis compression
69 COMPRESSION:NONE No compression
70 PROTOCOL:NONE Asynchronous mode
77 PROTOCOL:LAP-M Error control mode with LAP-M protocol
80 PROTOCOL:ALT Error control mode with MNP protocol
128 MODEM IN USE Modem already in use for this or another application.
W Dial tone detect
The W modifier makes the modem detect a dial tone before sending the next digit.
Wn Negotiation Progress result codes
The ATW setting determines whether progress result codes are displayed in addition to the ATX codes. Register S95 determines which progress result codes will be displayed.
0 - Progress codes 40 through 80 disabled.
1 - Progress codes 40 through 80 enabled. (default)
2 - Progress codes enabled; identical to W1.
When writing a CCL script, pay attention to result codes for scripts that require a specific response. If progress codes are enabled, the following strings appear on the screen during a connection (in this example, V.22 bis connection with no error control):
CARRIER 2400
PROTOCOL:NONE
CONNECT 2400
Xn Active result code
The result codes listed in Vn are divided into subsets that can be selected by the X command. Dial tone detection is enabled by X2 and X4. Busy tone detection is enabled by X3 and X4. The commands X0, X1, and X3 are appropriate for blind dialing. Blind dialing means the modem dials out even though a dial tone cannot be detected.
0 - Selects result codes 0 through 4 and 8
     (CONNECT, NO CARRIER ,and RING)
1 - Selects result codes 0 through 5, 8, and 10 through 28
     (for example, CONNECT 2400).
2 - Selects result codes 0 through 6, 8, and 10 through 28
     (connection speed, and DIALTONE detection)
3 - Selects result codes 0 through 5, 7, 8, and 10 through 28
     (connection speed and BUSY signal detection )
4 - Selects all result codes. (default)
Yn Longspace Disconnect
This command sets modem behavior for responding to a long break signal received from a remote modem:
Greater than 1.6 seconds for an asynchronous connection An attention frame for MNP or V.42.
0 - The modem ignores any long breaks received from the remote modem. (default)
1 - On receiving a long break from the remote modem, the modem goes on-hook (hangs up), and returns to command state.
2 - On receiving a long break from the remote modem, the modem returns to command state, but remains connected to the remote modem (does not hang up).
   Zn Reset
The Z command tells the modem to perform a software reset.
0 - Loads Profile 0 into the active profile.
1 - Loads Profile 1 into the active profile.

Dial Commands
, Pause
The comma (,) modifier introduces a delay time before dialing the next dial character or executing the next character in the dial string. The pause time is the value of the S8 register, (default=2 seconds).
   : Calling Card tone detect (:)
Same as W. The colon can detect most calling card tones. Place the colon in the dial string when you want to detect a wider range of frequencies.
@ Wait for quiet answer before dialing
For the time specified in the S7 register (default=50 seconds), the modem attempts to detect 5 seconds of silence. 		  ! Flash
The exclamation point (!) causes the modem to go on-hook then back off-hook, as if the receiver on the telephone set had been pressed momentarily.
; Return to local command state after dialing
The semicolon (;) modifier forces the modem back to the local command state. Placing a semicolon at the end of the dial string permits using the modem as a dialer and dialing in two or more steps. You may also force the modem to ignore the dial tone (blind dialing) by starting the dial string with ";D". This modifier may also be used in Fax Sender, AppleLink, and other communications applications. 		  R Reverse mode
The R modifier changes the modem from originate mode to answer mode after the dialing process is complete. This command is used only at the end of the dial string.
P Pulse dialing / Enable pulse dialing
When "P" is used as a subcommand of the "D" command
(ATDP 12345) this command selects pulse dialing, with the dialing speed fixed at 10 pulses per second.

When it is used as ATP it sets the default dialing mode to pulse mode. 		  T Touch-Tone dialing / Enable tone (DTMF dialing)
When "T" is used as a subcommand of the "D" command
(ATDT 12345) this causes all following numbers to be Touch-Tone dialed (default).

When it is used as ATT it sets the default dialing mode to Touch-Tone mode. Can be used in dial string (default).
S=n Dial telephone number stored at location n
Dials telephone number stored in location n, where n is 0, 1,or 2. You must have previously saved the value with the AT&Z command.

      

Advanced
&An

Answering / Originating mode
0 - When auto-answering, connect as answering modem.
1 - When auto-answering, connect as originating mode.

   &Cn DCD options
0 - Presence of carrier detect signal is assumed
     (ROM default. This value is recalled after &F is issued)
1 - Track status of carrier detect signal.
2 - Presence of carrier detect signal is assumed until on-line.
     From that point, track status of signal.

Apple bus modems have no DTE-DCE serial interface, this command has no effect and remains for scripting compatibility. 0-2 Return OK.
&Dn DTR options
0 - Status of DTR signal is ignored. (ROM Default. This value is recalled after &F is issued)
1 - DTR signal is monitored. The modem enters command state after an on-to-off transition of DTR signal. If the connection is intact, the O0 command returns to the on-line state.
2 - DTR signal is monitored. The modem hangs up and enters command state after an on-to-off transition of DTR signal.
3 - DTR signal is monitored. The modem hangs up and resets after an on-to-off transition of DTR signal.

Apple bus modems do not have a DTR line. For bus modems, an on-to-off DTR transition occurs when you close the connection tool or the application currently using the modem. In this case, the modem goes on-hook. This command has no effect and remains for scripting compatibility. 0-3 Return OK. Default value is 3.		 &Gn Guard tones
This command specifies whether guard tones should be transmitted. Guard tones are used in some telephone systems to allow proper data transfer over the network. Guard tones are not used in the United States.

0 - Disables guard tone. (default)
     (Not supported in Netherlands, Norway, Sweden,
      Switzerland, or the United Kingdom)

1 - Same as 2.

2 - Sends 1800 Hz guard tone.
&F

Recall factory configured default profile
The current active profile is replaced by the default factory configuration.

   &Jn Telco Jacks
0 - Configure for RJ-11, RJ-41S, RJ-45S telco jacks
1 - Configure for RJ-12, RJ-13 telco jacks (Not supported in
     Netherlands, Norway, Sweden, Switzerland, or the UK)
&Kn Local flow control
This command specifies which kind of local flow control is used.
0 - Local flow control disabled
1 - RTS/CTS local flow control enabled
2 - XON/XOFF local flow control enabled
3 - RTS/CTS local flow control enabled
4 - XON/XOFF local flow control enabled
5 - Transparent XON/XOFF local flow control enabled

Since Apple bus modems have built-in flow control mechanisms between the DTE and the DCE, this command has no effect. Flow control characters generated by the application software are always passed to the line.
This command has no effect and remains for scripting compatibility. 0-5 Respond OK, no action taken.

   &Ln Switched/Leased line
This command affects the modems behavior during the call setup and the carrier handshake phases at the beginning of a connection.
0 - Selects switched (dial-up) line. (default)
1 - Selects conditioned leased line (private speechband circuit)
&On X.25 PAD
Go to the X.25 PAD command state of channel n(n=0-3) from the AT command state. The modem will return to the command state of last channel selected, if a parameter for this command is not specified.
&Pn Pulse mode make/break ratio
0 - Sets the dial pulse make/break ratio at 39%/61%. (default)
1 - Sets the dial pulse make/break ratio at 33%/67%.

   &Qn Connection mode
This command allows you to enable and disable error control mode. The &Q command setting has precedence over \N command setting and registers S36 and S48.

0 - Asynchronous mode 0 - (no error control, disables V.42 and MNP)

1 - Asynchronous mode 1 - Async-to-Sync
2 - Asynchronous mode 2 - Stored Number Dial
3 - Asynchronous mode 3 - Voice/Data Switch
4 - Asynchronous mode 4 - Hayes AutoSync

5 - Error control mode Instructs the modem to make a connection using V.42/MNP, and fallback as necessary. (See S36 and S48 registers) (default)

6 - For interfaces requiring constant speed between the DTE (computer/terminal) and the DCE (modem), communicate in asynchronous mode with automatic speed buffering (ASB)
&Rn CTS/RTS
0 - Track CTS according to RTS
1 - Assume CTS (ignore RTS)

Apple bus modems have no DTE-DCE serial interface, this command has no effect and remains for scripting compatibility. 0-1 Return OK.
&Sn DSR
0 - Assert DSR signal always.
1 - Assert DSR signal before handshake only.
2 - After handshake negotiation, assert DSR signal, but before
     CONNECT XXXXX result code is sent to the DTE.

Apple bus modems have no DTE-DCE serial interface, this command has no effect and remains for scripting compatibility. 0-2 Return OK.
&Tn Self-tests
The following diagnostic tests are provided. These tests are available only when no error protocol is engaged. The duration of each test is controlled by register S18.

0 - Terminate the test. Used to terminate (escape from) a test in progress and return to command state, if S18=0.

1 - Local analog loopback. Initiates a local analog loopback test. The escape sequence must be entered to terminate this test. This mode tests the local modem and the local data terminal equipment.

3 - Local digital loopback. Initiates a local digital loopback test. The modem echoes characters back to the remote modem exactly as received.

4 - Enable the remote digital loopback. Enables the modem to respond to a remote modem attempting to place it in digital loopback test. If a remote modem places the local modem in remote digital loopback mode, the local modem echoes characters back to the remote modem exactly as received from the remote modem.

5 - Disable the remote digital loopback. Disables the modem from responding to a remote modem attempting to place it in the digital loopback mode.

6 - Remote digital loopback test. In this mode, characters sent to the remote modem are echoed back to the local modem exactly as they were received by the remote modem. This mode tests both local and remote modems and the telephone circuits.

7 - Remote digital loopback with self-test. Initiates a Remote Digital Loopback (like &T6) with self-test data pattern generation and error checking.

8 - Local analog loopback with self-test. Initiates a Local Analog Loopback (like &T1) with self-test data pattern generation and error checking. The tests terminate when an AT&T0 command is issued or when register S18 expires. In the self-test mode, an error counter counts the number of errors and sends the final result to the host at the end of the test. The maximum number of errors that can be counted is 255.

19 - Find out if RTS and CTS circuits are supported in the DTE cable.

Note: &T1 takes an optional parameter (a single character, A or O) to indicate whether the analog loopback must be done in originate (default) or answer mode. The modem must be configured for &Q0 (unbuffered asynchronous mode) for the &T commands to be entered. For &T19 to work, it must be supported by the terminal software.		   &Un Trellis coding Enable/Disable
Trellis code modulation in CCITT V.32 9600 bps only.
0 - Enable Trellis coding. (default)
1 - Disable Trellis coding.
&V Display profiles
Displays the following information:
Active profile
Stored profile 0
Stored profile 1
Stored telephone numbers (See AT&Z.)
&Wn Profile saving
This command saves the current active profile:
0 - Saves the active profile into profile 0.
1 - Saves the active profile into profile 1.
&Xn

Synchronous clock source
0 - Derive transmit clock signal from modem's internal oscillator (internal clock signal on pin 15)

1 - Derive transmit clock signal from attached computer (external clock signal on pin 24)

2 - Derive transmit clock signal from receive carrier (slave receive clock signal on pin 15)

On Apple bus modem - Ignored. Always returns OK. The modem does not support synchronous modes.
&Yn Specify start-up profile
Allows choosing between two different configurations at start-up.
0 - Specifies saved profile 0 as start-up configuration.
1 - Specifies saved profile 1 as start-up configuration.
&Zn=s Store phone number
Stores the dial string s (64 characters maximum) in location n. The value of n can be equal to 0, 1, or 2. Note that the dial string s is constructed in the same fashion as the ATD command. It therefore must be the last command on the command line and have no other characters following the dial string.

MNP-specific AT commands
\Bn

Send break
Send a break on the line for n times 100 milliseconds (n ranges from 1 to 9).

   %Cn Compression enable
Enables/disables MNPClass 5 data compression during MNP reliable connections.
0 - Disables data compression.
1 - Enables MNP 5 data compression. (default)
\Gn DCE flow control
Enables/disables modem-to-modem flow control. Coupled with \X, which determines if flow control characters are passed through or filtered.
0 - Disables modem-to-modem flow control. (default)
1 - Enables modem-to-modem flow control.


   \Nn MNP feature selection
Determines whether MNPerror control is used in connections. The \N command setting also updates register S36. The &Q command setting has precedence over \N command setting and registers.

0-1 Normal mode MNP disabled.

2 - Reliable mode. The modem will interrogate the remote modem for MNPcapabilities. If the remote modem does not support MNP, the local modem hangs up.

3 - Auto-reliable mode (default). The modem interrogates the remote modem for MNPcapabilities. If the remote modem supports MNP, a reliable connection is established. If the remote modem does not support MNP, a normal connection is established.
\O MNP link negotiation
Treated as ATO0 command. Modem returns to on-line state. MNP Link is not negotiated.
\U MNP link negotiation
Treated as ATO0 command. Modem returns to on-line state. MNP link is not terminated.		   \Tn Inactivity timer
Where n is a decimal integer between 0 and 90 specifying minutes. Sets the number of minutes the modem waits before automatically hanging up when data is not sent or received. The default option n=0 disables the timer.
\Xn Flow control processing
0 - No pass-through flow control. If modem-to-modem flow control is enabled, AT\G1, XON/XOFF characters received from the line are filtered out of the data stream; they are not passed to the DTE. (default)
1 - Pass-through flow control. If modem-to-modem flow control is enabled, AT\G1, XON/XOFF flow control characters received from the line are passed through to the DTE. 		  \Vn MNP result code
0 - Disables modified MNP result codes. (default)
1 - Enables modified standard MNP result codes 24 to 28.
2 - Returns OK; no effect.
\Z MNP termination
Treated as ATO0 command. Modem returns to on-line state. MNP link is not negotiated.
   \Y MNP link signaling
Treated as ATO0 command. Modem returns to on-line state. MNP link is not negotiated.

S registers
    Default Range Units
S0 Number of rings to auto answer 0 0:255 Number of rings
S1 Ring counter 0 0:255 Number of rings
S2 Escape Character 43<+> 0:127 ASCII Decimal
S3 Line-termination character 13 0:127 ASCII Decimal
S4 Line-feed character 10 0:127 ASCII Decimal
S5 Backspace character 8 0:127 ASCII Decimal
S6 Initial blind dialing wait 2 2:255 Seconds
S7 Carrier wait 50 1:255 Seconds
S8 Pause time 2 0:255 Seconds
S9 Carrier detect response time 6 1:255 1/10 second
S10 Disconnect timing 14 1:255 1/10 second
S11 Duration and spacing for DTMF dialing
Register S11 is preset and should remain unchanged to
assure correct dialing. 		95 50:255 Milliseconds
S12 Escape code guard time 50 20:255 1/50 second
S18 Self-test duration 0 0:255 Seconds
S36 Negotiation failure treatment
Specifies action that should be taken when an attempt to connect in error-control mode fails.
0 - Attempts V.42 connection. Hangs up if remote modem doesn't support V.42.
3 - Makes asynchronous connection. No error control. Same as AT&Q0.
4 - Attempts V.42 connection. If attempt fails, attempts MNP 2.4 connection. If attempt fails, then hangs up.
5 - Attempts V.42 connection. If attempt fails, attempts MNP 2.4 connection. If attempt fails, then attempts asynchronous connection. (default)

 5 0/3/4/5 Settings
S37 Desired DCE connection speed
This value is used in conjunction with the ATN and ATB values to determine which modulations are attempted whe connecting.
 0 -  Auto-mode Attempts to connect at the highest possible speed. (default)
 3 -  Attempts to connect at 300 bps.
 5 -  Attempts to connect at 1200 bps.
 6 -  Attempts to connect at 2400 bps.
 7 -  Attempts to connect at 4800 bps.
 8 -  Attempts to connect at 7200 bps.
 9 -  Attempts to connect at 9600 bps.
10 - Attempts to connect at 12000 bps.
11 - Attempts to connect at 14400 bps.

 0 0/3:11 Settings
S38 Delay before hang up 0 0:254 Seconds
S46

V.42 bis data compression selection

136 - V.42 only
138 - V.42 with V.42 bis compression. (default)

 138 136/138 Settings
S48

Feature negotiation action
Selects which error control features are allowed when making connections.
0 - Negotiation disabled: try only V.42.
3 - Negotiation enabled without detection phase.
7 - Negotiation enabled with detection phase. (default)
128 - Negotiation disabled: try MNP only. V.42 disabled.

 7 0/3/7/128 Settings
S95

Error control negotiation message option
A bit map to enable different result codes. Linked to ATW when ATW=1.
Bit Value  Meaning
0
1  -  1- not used
2  -  4- Enables CARRIER messages only.
3  -  8- Enables CARRIER+PROTOCOL messages only.
4  -16- not used
5  -32- Enables CARRIER+PROTOCOL+COMPRESSION messages. (default)

32 4/8/32 Bits