6 Call control commands and methods

07.073GPPAT Command set for GSM Mobile Equipment (ME)Release 1998TS

This clause describes the control of GSM calls. Normal data and fax call control is done as in ITU‑T Recommendations V.25ter [14], T.31 [11] and T.32 [12]. For voice call originating, refer subclause "ITU‑T V.25ter dial command D".

6.1 Select type of address +CSTA

Table 12: +CSTA parameter command syntax

Command

Possible response(s)

+CSTA=[<type>]

+CSTA?

+CSTA: <type>

+CSTA=?

+CSTA: (list of supported <type>s)

Description

Set command selects the type of number for further dialling commands (D) according to GSM specifications. Test command returns values supported by the TA as a compound value.

Defined values

<type>: type of address octet in integer format (refer GSM 04.08 [8] subclause 10.5.4.7); default 145 when dialling string includes international access code character "+", otherwise 129

Implementation

Mandatory when other than default value allowed.

6.2 ITU‑T V.25ter [14] dial command D

V.25ter [14] dial command D lists characters that may be used in a dialling string for making a call or controlling supplementary services in accordance with GSM 02.30 [19]. Their use in GSM is listed in this subclause, as well as new dial modifiers applicable only to GSM are introduced. For a ME supporting AT commands only, it is mandatory to support the control of supplementary services in accordance with GSM 02.30 through the dial command or through the specific supplementary service commands (+CCFC, +CLCK, etc.), where GSM 02.30 identifies the supplementary services as mandatory.

V.25ter dialling digits

1 2 3 4 5 6 7 8 9 0 * # + A B C (implementation of these characters is mandatory for GSM)

D (implementation of this character is optional for GSM, and it is ignored)

V.25ter modifier characters

, (implementation of this character is mandatory for GSM, but it may be ignored)

T P (implementation of these characters is mandatory for GSM, but they are ignored)

! W @ (implementation of these characters is optional for GSM, and they are ignored)

V.25ter semicolon character

In GSM, when semicolon character is given after dialling digits (or modifiers), a voice call originated to the given address. TA returns to command state immediately (or after possible +COLP result code; refer subclause "Connected line identification presentation +COLP"). Refer Annex G for a detailed example.

GSM modifier characters

> (refer subclause "Direct dialling from phonebooks")

I or i (override the CLIR supplementary service subscription default value for this call; I = invocation (restrict CLI presentation) and i = suppression (allow CLI presentation); refer subclause "Calling line identification restriction +CLIR")

G or g (control the CUG supplementary service information for this call; uses index and info values set with command +CCUG; refer subclause "Closed user group +CCUG")

6.3 Direct dialling from phonebooks

GSM ME and SIM can contain phonebooks which have a phone number and an alphanumeric field for each phonebook entry location. The use of V.25ter [14] dialling command ensures that direct dialling from ME and SIM phonebook is possible through ordinary communications software which just gives the phone number field to be filled and then use the D command to originate the call. Available memories may be queried with Select Phonebook Storage test command +CPBS=?, and location range for example with Read Phonebook Entries test command +CPBR=?.

Execute commands

1. D><str>[I][G][;] originate call to phone number which corresponding alphanumeric field is <str> (if possible, all available memories should be searched for the correct entry)

2. D>mem<n>[I][G][;] originate call to phone number in memory mem entry location <n> (available memories may be queried with Select Phonebook Storage test command +CPBS=?; mem could be e.g. ME)

3. D><n>[I][G][;] originate call to phone number in entry location <n> (it is manufacturer specific which memory storage of ME, SIM and TA is used; command Select Phonebook Memory Storage +CPBS setting is recommended to be used)

Semicolon character shall be added when voice call is originated. CLIR and CUG per call base modifiers may also be present.

Responses

Possible error responses include +CME ERROR: <err> when error is related to ME functionality. Refer subclause 9.2 for possible error values. Otherwise TA responses can have values defined by V.25ter [14] and commands Service Reporting Control +CR and Connected Line Identification Presentation +COLP. Detailed error report of an unsuccessful originated call failed in a GSM network error can be obtained with command Extended Error Report +CEER (if implemented).

Defined values

<str>: string type value, which should equal to an alphanumeric field in at least one phonebook entry in the searched memories; used character set should be the one selected with Select TE Character Set +CSCS

<n>: integer type memory location should be in the range of locations available in the memory used

Implementation

Mandatory when direct dialling is implemented. Also phonebook commands implementation is required.

6.4 Call mode +CMOD

Table 13: +CMOD parameter command syntax

Command

Possible response(s)

+CMOD=[<mode>]

+CMOD?

+CMOD: <mode>

+CMOD=?

+CMOD: (list of supported <mode>s)

Description

Set command selects the call mode of further dialling commands (D) or for next answering command (A). Mode can be either single or alternating (in the present document, terms "alternating mode" and "alternating call" refer to all GSM bearer and teleservices that incorporate more than one basic service (voice, data, fax) within one call). When single mode is selected the call originating and hangup procedures are similar to procedures specified in ITU‑T Recommendations V.25ter [14], T.31 [11] and T.32 [12]. In GSM there can be voice followed by data (refer GSM 02.02 [1]), alternating voice/data (refer GSM 02.02 [1]) and alternating voice/fax calls (refer GSM 02.03 [2]). Refer next two subclauses for alternating call control methods.

Test command returns values supported by the TA as a compound value.

NOTE: +CMOD shall be set to zero after a successfully completed alternating mode call. It shall be set to zero also after a failed answering. The power‑up, factory (&F) and user resets (Z) shall also set the value to zero. This reduces the possibility that alternating mode calls are originated or answered accidentally.

Defined values

<mode>:

0 single mode

1 alternating voice/fax (teleservice 61)

2 alternating voice/data (bearer service 61)

3 voice followed by data (bearer service 81)

also all other values below 128 are reserved by the present document

Implementation

Mandatory when alternating mode calls are implemented in the TA.

6.5 Hangup call +CHUP

Table 14: +CHUP action command syntax

Command

Possible response(s)

+CHUP

+CHUP=?

Description

Execution command causes the TA to hangup the current GSM call of the ME.

NOTE: The purpose of this command is not to replace the V.25ter [14] command H, but to give an assured procedure to terminate an alternating mode call. Refer next subclause.

Implementation

Mandatory when alternating mode calls implemented in the TA.

6.6 Alternating mode call control method

This subclause describes the procedure to handle alternating mode calls with AT commands. Procedures are mandatory when alternating mode calls are implemented in the TA.

NOTE: ATH and drop DTR will not necessarily cause a hangup from voice mode. If the +CVHU $(AT R97)$ is implemented the behaviour shall be controlled by its setting.

Voice followed by data call (bearer service 81)

Figure 8 shows commands to start the call, to switch from voice to data (In‑Call Modification) and to hang up the call. +CMOD and +FCLASS commands indicate the current settings before dialling or answering command, not that they shall be given just before D or A command. Refer subclause "Cellular result codes +CRC" for possible +CRING result code values. Refer Annex F for a detailed example.

Figure  9: Voice followed by data call

Voice/ data call (bearer service number 61)

Figure 10 shows the commands to start the call, to switch between modes (In‑Call Modification) and to hang up the call. +CMOD and +FCLASS commands indicate the current settings before dialling or answering command, not that they shall be given just before D or A command. Refer subclause "Cellular result codes +CRC" for possible +CRING result code values. Refer Annex E for a detailed example.

Figure  11: Alternating voice and data call

Voice/ fax call (teleservice number 61)

Figure 12 shows the commands to start the call, to switch between modes (In‑Call Modification) and to hang up the call. +CMOD and +FCLASS commands indicate the current settings before dialling or answering command, not that they shall be given just before D or A command. The parameter "x" of +FCLASS command can be 1, 1.0, 2 or 2.0.

NOTE: The transition from fax mode to voice mode is for further study.

Figure  13: Alternating voice and fax call

6.7 Select bearer service type +CBST

Table 15: +CBST parameter command syntax

Command

Possible response(s)

+CBST=[<speed>[,<name>[,<ce>]]]

+CBST?

+CBST: <speed>,<name>,<ce>

+CBST=?

+CBST: (list of supported <speed>s),(list of supported <name>s),(list of supported <ce>s)

Description

Set command selects the bearer service <name> with data rate <speed>, and the connection element <ce> to be used when data calls are originated (refer GSM 02.02 [1]). Values may also be used during mobile terminated data call setup, especially in case of single numbering scheme calls (refer +CSNS).

Test command returns values supported by the TA as compound values.

Defined values

NOTE: The default values of the subparameters are manufacturer specific since they depend on the purpose of the device and data services provided by it. Not all combinations of these subparameters are supported by GSM (refer GSM 02.02 [1]).

<speed>:

0 autobauding (automatic selection of the speed; this setting is possible in case of 3.1 kHz modem and non-transparent service)

1 300 bps (V.21)

2 1200 bps (V.22)

3 1200/75 bps (V.23)

4 2400 bps (V.22bis)

5 2400 bps (V.26ter)

6 4800 bps (V.32)

7 9600 bps (V.32)

12 9600 bps (V.34)

14 14400 bps (V.34)

15 19200 bps (V.34)

16 28800 bps (V.34)

34 1200 bps (V.120)

36 2400 bps (V.120)

38 4800 bps (V.120)

39 9600 bps (V.120)

43 14400 bps (V.120)

47 19200 bps (V.120)

48 28800 bps (V.120)

49 38400 bps (V.120)

50 48000 bps (V.120)

51 56000 bps (V.120)

65 300 bps (V.110)

66 1200 bps (V.110)

68 2400 bps (V.110 or X.31 flag stuffing)

70 4800 bps (V.110 or X.31 flag stuffing)

71 9600 bps (V.110 or X.31 flag stuffing)

75 14400 bps (V.110 or X.31 flag stuffing)

79 19200 bps (V.110 or X.31 flag stuffing)

80 28800 bps (V.110 or X.31 flag stuffing)

81 38400 bps (V.110 or X.31 flag stuffing)

82 48000 bps (V.110 or X.31 flag stuffing)

83 56000 bps (V.110 or X.31 flag stuffing)

115 56000 bps (bit transparent)

116 64000 bps (bit transparent)

also all other values below 128 are reserved by the present document

<name>:

0 data circuit asynchronous (UDI or 3.1 kHz modem)

1 data circuit synchronous (UDI or 3.1 kHz modem)

2 PAD Access (asynchronous) (UDI)

3 Packet Access (synchronous) (UDI)

4 data circuit asynchronous (RDI)

5 data circuit synchronous (RDI)

6 PAD Access (asynchronous) (RDI)

7 Packet Access (synchronous) (RDI)

also all other values below 128 are reserved by the present document

<ce>:

0 transparent

1 non-transparent

2 both, transparent preferred

3 both, non-transparent preferred

Implementation

Mandatory when data calls implemented.

6.8 Radio link protocol +CRLP

Table 16: +CRLP parameter command syntax

Command

Possible response(s)

+CRLP=[<iws>[,<mws>[,<T1>[,<N2>[,<ver>[,<T4>]]]]]]

+CRLP?

+CRLP: <iws>,<mws>,<T1>,<N2>[,<ver1>[,<T4>]]

[<CR><LF>+CRLP: <iws>,<mws>,<T1>,<N2>[,<ver2>[,<T4>]]

[…]]

+CRLP=?

+CRLP: (list of supported <iws>s),(list of supported <mws>s),

(list of supported <T1>s),(list of supported <N2>s)[,<ver1>

[,(list of supported <T4>s)]]

[<CR><LF>+CRLP: (list of supported <iws>s),(list of supported

<mws>s),(list of supported <T1>s),(list of supported <N2>s)

[,<ver1>[,(list of supported <T4>s)]]

[…]]

Description

Radio link protocol (RLP) parameters used when non-transparent data calls are originated may be altered with set command. Available command subparameters depend on the RLP versions implemented by the device (e.g. <ver> may not be available if device supports only versions 0 and 1).

NOTE: If radio link protocol is not used, but some other error correcting protocol (for transparent data calls), V.25ter [14] Error Control Selection test command +ES=? may be used to indicate the presence of the protocol.

Read command returns current settings for each supported RLP version <verx>. Only RLP parameters applicable to the corresponding <verx> are returned.

Test command returns values supported by the TA as a compound value. If ME/TA supports several RLP versions <verx>, the RLP parameter value ranges for each <verx> are returned in a separate line.

Defined values

<ver>, <verx>: RLP version number in integer format; when version indication is not present it shall equal 0

NOTE: Versions 0 and 1 share the same parameter set. Read and test commands shall return only one line for this set (where <verx> is not present).

<iws>, <mws>, <T1>, <N2>, <T4>: IWF to MS window size, MS to IWF window size, acknowledgement timer T1, retransmission attempts N2, re-sequencing period T4 in integer format (default values and value ranges depend on RLP version; refer GSM 04.22 [18]): T1 and T4 are in units of 10 ms.

Implementation

Mandatory when RLP implemented.

6.9 Service reporting control +CR

Table 17: +CR parameter command syntax

Command

Possible response(s)

+CR=[<mode>]

+CR?

+CR: <mode>

+CR=?

+CR: (list of supported <mode>s)

Description

Set command controls whether or not intermediate result code +CR: <serv> is returned from the TA to the TE. If enabled, the intermediate result code is transmitted at the point during connect negotiation at which the TA has determined which speed and quality of service will be used, before any error control or data compression reports are transmitted, and before the intermediate result code CONNECT is transmitted.

NOTE: This command replaces V.25ter [14] command Modulation Reporting Control +MR, which is not appropriate for use in the GSM network. Possible error control (other than radio link protocol) and data compression reporting can be enabled with V.25ter commands Error Control Reporting +ER and Data Compression Reporting +DR.

Test command returns values supported by the TA as a compound value.

Defined values

<mode>:

0 disables reporting

1 enables reporting

<serv>:

ASYNC asynchronous transparent

SYNC synchronous transparent

REL ASYNC asynchronous non‑transparent

REL SYNC synchronous non‑transparent

GPRS [<L2P>] GPRS

The optional <L2P> proposes a layer 2 protocol to use between the MT and the TE. It is defined in the Enter GPRS Data Mode (+CGDATA) command.

Implementation

Mandatory when data calls implemented.

6.10 Extended error report +CEER

Table 18: +CEER action command syntax

Command

Possible response(s)

+CEER

+CEER: <report>

+CEER=?

Description

Execution command causes the TA to return one or more lines of information text <report>, determined by the ME manufacturer, which should offer the user of the TA an extended report of the reason for

  • the failure in the last unsuccessful call setup (originating or answering) or in‑call modification,
  • the last call release,
  • the last unsuccessful GPRS attach or unsuccessful PDP context activation,
  • the last GPRS detach or PDP context deactivation.

Typically, the text will consist of a single line containing the cause information given by GSM network in textual format.

Defined values

<report>: the total number of characters, including line terminators, in the information text shall not exceed 2041 characters.

Text shall not contain the sequence 0<CR> or OK<CR>

Implementation

Optional.

6.11 Cellular result codes +CRC

Table 19: +CRC parameter command syntax

Command

Possible response(s)

+CRC=[<mode>]

+CRC?

+CRC: <mode>

+CRC=?

+CRC: (list of supported <mode>s)

Description

Set command controls whether or not the extended format of incoming call indication or GPRS network request for PDP context activation is used. When enabled, an incoming call is indicated to the TE with unsolicited result code +CRING: <type> instead of the normal RING.

Test command returns values supported by the TA as a compound value.

NOTE: Similar command may be found in TIA IS‑99 [15] and TIA IS‑135 [16].

Defined values

<mode>:

0 disables extended format

1 enables extended format

<type>:

ASYNC asynchronous transparent

SYNC synchronous transparent

REL ASYNC asynchronous non‑transparent

REL SYNC synchronous non‑transparent

FAX facsimile (TS 62)

VOICE normal voice (TS 11)

VOICE/XXX voice followed by data (BS 81) (XXX is ASYNC, SYNC, REL ASYNC or REL SYNC)

ALT VOICE/XXX alternating voice/data, voice first (BS 61)

ALT XXX/VOICE alternating voice/data, data first (BS 61)

ALT VOICE/FAX alternating voice/fax, voice first (TS 61)

ALT FAX/VOICE alternating voice/fax, fax first (TS 61)

GPRS <PDP_type>, <PDP_addr>[, <L2P>] GPRS network request for PDP context activation

<PDP_type> and <PDP_addr> are as defined in the Define PDP Context (+CGDCONT) command. The optional <L2P> proposes a layer 2 protocol to use between the MT and the TE. It is defined in the Enter GPRS Data Mode (+CGDATA) command. If the MT is unable to announce to the TE the network’s request (for example it is in V.25ter online data state) the MT shall reject the request. No corresponding unsolicited result code shall be issued when the MT returns to a command state.

Implementation

Mandatory when data or fax circuit mode calls implemented.

6.12 HSCSD device parameters +CHSD

Table 20: +CHSD action command syntax

Command

Possible response(s)

+CHSD

+CHSD: <mclass>,<maxRx>,<maxTx>,<sum>,<codings>

+CME ERROR: <err>

+CHSD=?

Description

Execution command returns information about HSCSD features (refer GSM 02.34 [29]) supported by the ME/TA. Refer subclause 9.2 for possible <err> values.

Defined values

<mclass>: integer type; multislot class

<maxRx>: integer type; maximum number of receive timeslots that ME can use

<maxTx>: integer type; maximum number of transmit timeslots that ME can use

<sum>: integer type; total number of receive and transmit timeslots that ME can use at the same time (per TDMA frame). The following applies in a HSCSD call: 1  (receive slots) + (transmit slots)  <sum>

<codings> is a sum of integers each representing a supported channel coding (e.g. value 5 indicates that 4.8k and 9.6k channel codings are supported):

1 4.8k full rate data traffic channel

4 9.6k full rate data traffic channel

8 14.4k full rate data traffic channel

Implementation

Mandatory when HSCSD implemented.

6.13 HSCSD transparent call configuration +CHST

Table 21: +CHST parameter command syntax

Command

Possible response(s)

+CHST=[<wRx>[,<codings>]]

+CHST?

+CHST: <wRx>,<codings>

+CHST=?

Description

Set command controls parameters for transparent HSCSD calls. Changing them during a call does not affect the current call.

Defined values

<wRx>: integer type; wanted amount of receive timeslots. Default value 0 indicates that TA shall calculate a proper value from currently selected fixed network user rate (<speed> subparameter from +CBST command) and <codings>

<codings>: a sum of integers each representing a channel coding that is accepted for transparent HSCSD calls. Default value 0 indicates that all supported codings are accepted (refer +CHSD command for other values)

Implementation

Mandatory when transparent HSCSD implemented.

6.14 HSCSD non-transparent call configuration +CHSN

Table 22: +CHSN parameter command syntax

Command

Possible response(s)

+CHSN=[<wAiur>[,<wRx>[,<topRx>

[,<codings>]]]]

+CHSN?

+CHSN: <wAiur>,<wRx>,<topRx>,<codings>

+CHSN=?

+CHSN: (list of supported <wAiur>s), (list of supported <wRx>s),(list of supported <topRx>,(list of supported <codings>s)

Description

Set command controls parameters for non-transparent HSCSD calls. Changing <topRx> or <codings> value during a call does not affect the current call. Changing of <wAiur> or <wRx> affects the current call only if <topRx> was non-zero when call was established.

Defined values

<wAiur>: integer type; wanted air interface user rate. Default value 0 indicates that TA shall calculate a proper value from currently selected fixed network user rate (<speed> subparameter from +CBST command), <codings>, and <wRx> (or <maxRx> from +CHSD command if <wRx>=0). Other values:

1 9600 bps

2 14400 bps

3 19200 bps

4 28800 bps

5 38400 bps

6 43200 bps

7 57600 bps

<wRx>: integer type; wanted amount of receive timeslots. Default value 0 indicates that TA shall calculate a proper value from currently selected <wAiur> and <codings>

<topRx>: integer type; top value for <wRx> that user is going to request during the next established non-transparent HSCSD call. Default value 0 indicates that user is not going to change <wAiur>/<wRx> during the next call

<codings>: a sum of integers each representing a channel coding that is accepted for non-transparent HSCSD calls. Default value 0 indicates that all supported codings are accepted (refer +CHSD command for other values)

Implementation

Mandatory when non-transparent HSCSD implemented.

6.15 HSCSD current call parameters +CHSC

Table 23: +CHSC action command syntax

Command

Possible response(s)

+CHSC

+CHSC: <rx>,<tx>,<aiur>,<coding>

+CHSC=?

Description

Execution command returns information about current HSCSD call. If no HSCSD call is active, all parameters returned shall equal zero. (It is manufacturer specific whether non-zero information is returned in case of an active normal single-slot data call.)

Defined values

<rx>: integer type; number of receive timeslots currently in use

<tx>: integer type; number of transmit timeslots currently in use

<aiur>: integer type; current air interface user rate (in case of transparent service this equals fixed network user rate) (refer +CHSN command for possible values)

<coding>: current channel coding (refer +CHSD command for possible values)

Implementation

Optional.

6.16 HSCSD parameters report +CHSR$(AT R98)$

Table 24: +CHSR action command syntax

Command

Possible response(s)

+CHSR=[<mode>]

+CHSR?

+CHSR: <mode>

+CHSR=?

+CHSR: (list of supported <mode>s)

Description

Enabled command returns intermediate result code +CHSR: <type> from the TA to the TE when an HSCSD call is being set up. The result code represents the current (negotiated or renegotiated) HSCSD parameters. If enabled, the intermediate result code is transmitted at the point of the call setup negotiation where the TA has determined what type of an HSCSD connection will be used. Result code transmission is done after possible service (+CR), error control (+ER), and/or compression (+DR) reporting but before possible TE-TA rate (+ILRR) reporting and before the intermediate result code CONNECT is transmitted. The format of the intermediate result code is:

+CHSR: <rx>,<tx>,<aiur>,<coding>

For the value definitions, refer to +CHSN and +CHSC commands. For instance, for a non-transparent HSCSD call, result code ‘+CHSR: 2,2,4,8’ means that the call has two timeslots in both up- and downlink, the air interface user rate is 28800 bps, and the used channel coding TCH/F14.4.

Defined values

<mode>:

0 disables reporting

1 enables reporting

Implementation

Mandatory when HSCSD implemented

6.17 HSCSD automatic user initiated upgrading +CHSU$(AT R98)$

Table 25: +CHSU parameter command syntax

Command

Possible response(s)

+CHSU=<mode>

+CHSU?

+CHSU: <mode>

+CHSU=?

+CHSU: (list of supported <mode>s)

Description

Set command controls whether or not automatic user initiated service level upgrading shall be used for non-transparent HSCSD calls. "Automatic" means that, if enabled, the ME/TA shall use the UP bit in the received RLP frames to determine when to initiate user initiated service level upgrading (i.e. when to modify the +CHSN parameters <wAiur> and/or <wRx> for the current call). Refer to GSM 07.01 for details on the interpretation of the UP bit(s).

NOTE: The validity of the UP bit in the RLP frames depends on the result of the RLP negotiations. The UP bit shall only be used if the result of the RLP negotiations were successful with respect to the UP bit.

Defined values

<mode>:

0 disables use of UP bit for upgrading

1 enables use of UP bit for upgrading

Implementation

Optional

6.18 Single numbering scheme +CSNS

Table 26: +CSNS parameter command syntax

Command

Possible response(s)

+CSNS=[<mode>]

+CSNS?

+CSNS: <mode>

+CSNS=?

+CSNS: (list of supported <mode>s)

Description

Set command selects the bearer or teleservice to be used when mobile terminated single numbering scheme call is established. Parameter values set with +CBST command shall be used when <mode> equals to a data service. If +CBST parameter is set to a value that is not applicable to single numbering calls, ME/TA shall map the value to the closest valid one. E.g. if user has set <speed>=71, <name>=2 and <ce>=1 (non-transparent asynchronous 9600 bps V.110 ISDN connection) for mobile originated calls, ME/TA shall map the values into non-transparent asynchronous 9600 bps V.32 modem connection when single numbering scheme call is answered.

Test command returns values supported by the TA as compound values.

Defined values

<mode>:

0 voice

1 alternating voice/fax, voice first (TS 61)

2 fax (TS 62)

3 alternating voice/data, voice first (BS 61)

4 data

5 alternating voice/fax, fax first (TS 61)

6 alternating voice/data, data first (BS 61)

7 voice followed by data (BS 81)

Implementation

Optional.

6.19 Voice Hangup Control +CVHU $(AT R97)$

Table 27: +CVHU parameter command syntax

Command

Possible response(s)

+CVHU=[<mode>]

+CVHU?

+CVHU:<mode>

+CVHU=?

+CVHU:(list of supported <mode>s)

Description

Set command selects whether ATH or "drop DTR" shall cause a voice connection to be disconnected or not. By voice connection is also meant alternating mode calls that are currently in voice mode. (See section 6.6).

NOTE: When <mode> = 2, this command must be seen in conjunction with the V.25ter [14] command &D. Else &D shall be ignored.

Defined values

<mode>:

0 "Drop DTR" ignored but OK response given. ATH disconnects.

1 "Drop DTR" and ATH ignored but OK response given.

2 "Drop DTR" behaviour according to &D setting. ATH disconnects.

Implementation

Optional

6.20 V.120 rate adaption protocol +CV120

Table 28: +CV120 parameter command syntax

Command

Possible response(s)

+CV120=[<rah>[,<mfm>[,

<mode>[,<llineg>[,

<assign>[,<negtype>]]]]]]

+CV120?

+CV120: <rah>,<mfm>,<mode>,<llineg>,

<assign>,<negtype>

+CV120=?

+CV120: (list of supported <rah>s),(list of supported <mfm>s),(list of supported <mode>s),(list of supported <llineg>s),(list of supported <assign>s),(list of supported <negtype>s)

Description

Set command sets the values of the V.120 protocol parameters (defined in CCITT V.120) that are carried in the GSM BC and/or LLC information elements.

Read command returns current settings for the V.120 parameters.

Test command returns values supported by the TA as a compound value.

Defined values

<rah>

0 rate adaption header not included

1 rate adaption header included (mandatory for protocol sensitive modes).

<mfm>

0 multiple frame establishment not supported, only UI frames allowed

1 multiple frame establishment supported, both I and UI frames allowed.

<mode>

0 bit transparent mode of operation

1 protocol sensitive mode of operation.

<llineg>

0 no negotiation, LLI = 256 only

1 negotiation allowed. Note – <negtype> indicates the connection over which the negotiation is performed.

<assign>

0 message originator is "default assignee"

1 message originator is "assignor only".

<negtype>

0 negotiation is done using logical link zero

1 negotiation is done with USER INFORMATION messages on a temporary signalling connection.

GSM does not support all the possible modes of V.120 operation. However, in order to accommodate possible future additions, the complete set of parameters is included in the command.

The permitted values are: 1, 1 or 0, 1, 0, 0, 0.

A recommended set of default values is: 1, 1, 1, 0, 0, 0.

Implementation

Mandatory, if the ME supports V.120 interworking.

6.21 ITU‑T V.25ter [14] call control commands

Table 29: V.25ter call control commands

Command

Section

Impl.

Use in GSM

D[<dial_ string>][;]

6.3.1

mand.

originates a call

T

6.3.2

mand.

ignored (select tone dialling)

P

6.3.3

mand.

ignored (select pulse dialling)

A

6.3.5

mand.

answer a call

H[<value>]

6.3.6

mand.

hang‑up a single mode call; for alternate mode call refer subclause "Hangup call +CHUP" (only value equal to zero needed)

O[<value>]

6.3.7

mand.

returns TA to online data state from online command mode (only value equal to zero needed)

S0=[<value>]

6.3.8

mand.

sets the number of call indications (rings) before automatically answering the call; value equalling zero disables automatic answering and is the default

S6=[<value>]

6.3.9

mand.

ignored (pause before blind dialling)

S7=[<value>]

6.3.10

mand.

sets number of seconds to wait for completion of call answering or originating procedure before giving up and disconnecting

S8=[<value>]

6.3.11

mand.

sets number of seconds to wait when comma dial modifier encountered in dial string of D command (default is 2 seconds)

S10=[<value>]

6.3.12

mand.

sets number of tenths of seconds to wait before disconnecting after TA has indicated the absence of received line signal

L[<value>]

6.3.13

mand.

ignored (monitor speaker loudness)

M[<value>]

6.3.14

mand.

ignored (monitor speaker mode)

6.22 ITU‑T V.25ter [14] data compression commands

Table 30: V.25ter data compression commands

Command

Section

Impl.

Use in GSM

+DS=[<dir>[,<neg> [,<P1>[,<P2>]]]]

6.6.1

mand. when V.42bis

controls ITU‑T Recommendation V.42bis data compression functions; for subparameter defaults in GSM refer GSM 04.22 [18]

+DR=[<value>]

6.6.2

mand. when V.42bis

determines whether the use of V.42bis is informed using intermediate result code +DR: <type> before going online data state after call answering or originating

6.23 Informative examples

The alternating mode call handling (voice and fax, or voice and data) and the data call setup commands are defined such that the dialling command of V.25ter [14] (D) still always originates a call. The purpose is to support all current TE applications using the dialling command as default. Fax calls are controlled following the rules of ITU‑T T.31 [11] and T.32 [12] standards.

An example where a voice call is originated:

ATD+1 812 555673I; (type of address defaults to 145, CLI presentation is restricted for this call)

OK (call setup was successful)

An example where a voice call is attempted from a phonebook:

ATD>"Doe Joe"G; (enable CUG control for this call)

+CME ERROR: 22 (entry "Doe Joe" is not found)

Also supplementary services may be controlled using dial command according to GSM 02.30 [19]. An example of call forwarding on no reply for telephony with the adjustment of the no reply condition timer on 25 seconds:

ATD**61*+1812555673*11*25#

OK (modification was successful)

Two new commands are created for controlling the alternating mode calls. First one, Call Mode (+CMOD), selects between single and alternating mode. Because this is a crucial command, it is defined that the value is set back to zero (single mode) after every successfully originated alternating mode call. Also on power‑up and factory or user resets, the value is set to zero. The second new command, Hangup Call (+CHUP), is not a replacement of V.25ter [14] command H, but a command which reliably disconnects the call in GSM network. This is defined because the H command is used to switch from fax or data mode to voice mode.

The setting of GSM bearer service (data circuit duplex asynchronous and synchronous, PAD access circuit asynchronous, or data packet duplex synchronous), is done with Select Bearer Service Type (+CBST). It chooses one of the four mentioned bearer services, the data rate of the service (or actually the modulation when modem IWFs are used), and enables or disables RLP. Command Radio Link Protocol (+CRLP) is used to set the RLP parameters in the radio path.

Service Reporting Control command (+CR) is defined similarly as the reporting of modulation, V.18, error control, and data compression which are V.25ter [14] features used to show information about the type of the established connection before the CONNECT intermediate result code. +CR command has one subparameter which specifies whether the intermediate result code +CR: <serv> is returned or not. The result code should be returned before any V.25ter [14] reporting result codes. An example of setting up an asynchronous 9600 bit/s modem connection with service reporting:

AT+CBST=7,0,1 (asynchronous modem 9600 bit/s and RLP)

OK

AT+CR=1 (enable reporting)

OK

ATD1234567890

+CR: REL ASYNC

CONNECT 9600

As GSM network offers more information about the reason of the failure in call originating and answering than normal PSTN, it is useful to add an extra command to return this information to the TE. This information should not be returned always after unsuccessful call originating or answering, because many TE applications look for just the regular NO CARRIER, BUSY, NO ANSWER and CONNECT messages. Action command Extended Error Report (+CEER) does not have any subparameters, and it returns the cause of the latest call setup failure. This information may be the textual presentation of the GSM network failure code (refer GSM specification 04.08 [8] Annex H), or some other information defined by the TA manufacturer.