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Content for  TS 27.007  Word version:  18.0.0

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C  Commands from TIA IS-101p. 421

C.1  Introductionp. 421

The "Voice Control Interim Standard for Asynchronous DCE", TIA IS-101, contains some commands that are useful when passing audio "data" (that is, data which represents audio information) between the computer and the TA.
Some of the following clauses describe commands from IS-101 which are central to this TA application. However, with the exception of necessary extensions, these descriptions are not intended to replace the definitions found in IS-101. Other novel commands from the interim standard are not included because they are peripheral to TA operation.
The standard specifies the following modes:
  • command mode, where there is no transfer of audio "data" between the TA and the computer. In command mode, the computer is neither sending audio data to the TA nor receiving audio data from the TA.
  • transmit mode, where audio "data" is being transferred from the computer to the TA. No audio "data" is transferred from the TA to the computer in this state. A transition back to command mode occurs when an embedded command indicates "end of play" or "flush data", or an inactivity timer times out.
  • receive mode, where audio "data" is being transferred from the TA to the computer. No audio "data" is transferred from the computer to the TA in this state. A transition back to command mode occurs when any command is sent from the computer, or an inactivity timer times out. During the receive mode, the TA embeds result codes into the audio "data". These result codes indicate pertanent events such as "silence detected", "busy detected", and so on.
Strictly, the standard specifies another mode (translation), but this is not directly of interest here.
There are three possible levels of service:
  • a TA supporting level A performs the following operations and detects the following events: audio transmit, audio receive, DTMF detection, DTMF generation and single tone generation. The following indications are supported:
Event Description Handset state
3ringidle
4DTMF receivedidle
5receive buffer overrunreceive
6unsolicited fax requestidle
8phone on/off hookidle
9presumed hangupreceive
10presumed end of messagereceive
18ringbackidle
19busyidle
23playback buffer underruntransmit
25fax or data request acknowledgedidle
  • a TA supporting level B performs the operations and events of level A, and also supports DTMF detection while in the transmit state.
  • a TA supporting level C performs the operations and events of level B, and also supports double DTMF tone generation.
Since DTMF detection and generation cannot be guaranteed over current digital networks, it follows that none of the three levels of service can be supported.
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C.2  Commandsp. 422

C.2.1  Select mode +FCLASSp. 422

This command puts the TA into a particular mode of operation (data, fax, voice etc.). This causes the TA to process information in a manner suitable for that type of information (rather than for other types of information). The values and meanings of parameter <n> are specified in the following Table.
<n>
Mode
0
data
1
fax class 1 (TIA-578-A)
1.0
2
fax (manufacturer specific)
2.0
fax class 2 (ITU-T Recommendation T.32 [12] and TIA-592)
3...7
reserved for other fax modes
8
voice
9...15
reserved for other voice modes
16..79
reserved
80
VoiceView (Radish)
81..255
reserved
Command Return
+FCLASS=<n>
+FCLASS?<n>
+FCLASS=? (list of supported <n>s)
Voice mode is of particular interest here, and has an additional result code +VCON. Specifically, +VCON indicates that the TA is entering the voice command mode and there is a voice connection to at least one audio input or output. This presupposes that some mechanism has previously initiated a connection to that audio I/O.
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C.2.2  Buffer threshold setting +VBTp. 422

This refers to integers <lo> and <hi> that indicate levels within the TA transmit buffer at which flow control is asserted and deasserted. The buffer is used for averaging out the irregular timing of data from the computer, so that the data becomes synchronous and may be sent to some audio device.
Command Return
+VBT=<lo>,<hi>
+VBT? <lo>,<hi>
+VBT=? (list of supported <lo>s),(list of supported <hi>s),(buffer size)
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C.2.3  Calling number ID presentation +VCIDp. 423

The command refers to an integer that allows a called party to enable or disable (<n>=0) the reporting of the ID of calling parties, and specifies the method of presentation of the ID. This is basically the same as the supplementary service CLIP (Calling Line Identification Presentation). The presentation may be either formatted (<n>=1) or unformatted (<n>=2):
  • Formatted presentation: data items are reported in the form of <tag>=<value> pairs.
<tag> <value>
DATEMMDD (month, day)
TIMEHHMM (hour, minute)
NMBRcalling number or P or O (P = number is private, O = number is unavailable)
NAMEsubscription listing name
MESGdata from other (unknown) tags
  • Unformatted presentation: the data is presented in ASCII hex as printable numbers.
Command Return
+VCID=<n>
+VCID? <n>
+VCID=?(0-2)
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C.2.4  Receive gain selection +VGRp. 423

This refers to the amplification by the TA of audio samples sent from the TA to the computer. The command operates on an integer <n>, range 0...255. Values larger than 128 indicate a larger gain than nominal. Values less than 128 indicate a smaller gain than nominal. The entire range of 0...255 does not have to be provided. A value of zero implies the use of automatic gain control by the TA.
Command Return
+VGR=<n>
+VGR? <n>
+VGR=? (list of supported <n>s)
Up

C.2.5  Transmit gain selection +VGTp. 423

This refers to the amplification by the TA of audio samples sent from the computer to the TA. The command operates on an integer <n>, range 0...255. Values larger than 128 indicate a larger gain than nominal. Values less than 128 indicate a smaller gain than nominal. The entire range of 0...255 does not have to be provided. A value of zero implies the uses of automatic gain control by the TA.
Command Return
+VGT=<n>
+VGT? <n>
+VGT=? (list of supported <n>s)
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C.2.6  Initialise voice parameters +VIPp. 424

This recalls manufacturer determined settings <n> of voice parameters. The command is write only. The effect of the command is manufacturer specific.
Command Return
+VIP=<n>
+VIP=? (list of supported <n>s)
Up

C.2.7  Inactivity timer +VITp. 424

This refers to the value of the inactivity timer in the TA. It is used to monitor activity on the connection between the computer and the TA when the computer is in "transmit" mode and sending audio data to the TA. When the connection has been inactive for the time set by this command, the TA leaves "transmit" mode and reverts to command mode. An integer <n> different than zero implies a time of <n>/10 seconds. A value of zero disables the timer.
Command Return
+VIT=<n>
+VIT? <n>
+VIT=? (list of supported <n>s)
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C.2.8  Line selection +VLSp. 424

This determines the selection of sources and destinations of audio samples. An integer is used to label a particular combination of sources and destinations. The integer is defined in an entry in IS-101 which assumes as a model a TA, a local phone and a phone line. Two additional "manufacturer specific" configurations (16,17) are defined.
label=0
this is the idle state - the phone is not connected to the radio network and no audio paths are used.
label=1
the phone is connected to the radio network and no audio paths involving the internal microphone or internal loudspeaker are selected. This allows the computer to transmit audio data over the radio transmitter by selecting "transmit mode":
loudspeaker computer i/p transmit stage
microphone →
computer o/p →*
receiver stage →
This also allows the computer to receive audio data from the radio receiver by selecting "receive mode":
loudspeaker computer i/p transmit stage
microphone →
computer o/p →
receiver stage →*
label=4
the phone is not connected to the radio network but there is an audio path to the internal speaker. This allows the computer to play sound by selecting "transmit mode".
loudspeaker computer i/p transmit stage
microphone →
computer o/p →*
receiver stage →
label=6
the phone is not connected to the radio network but there is an audio path to the internal microphone. This allows the computer to record sound by selecting "receive mode".
loudspeaker computer i/p transmit stage
microphone →*
computer o/p →
receiver stage →
label=7
the phone is connected to the radio network. The internal microphone is connected to the radio transmitter. The radio receiver is connected to the internal loudspeaker. This allows the computer to enable normal phone operation (a human holding a conversation) by selecting command mode.
loudspeaker computer i/p transmit stage
microphone →*
computer o/p →
receiver stage →*
Command Return
+VLS=<n> +VCON
+VLS?<n>
+VLS=?complex; refer IS-101
+VCON is returned if an audio path is established or if a connection is made to the radio network.
Manufacturer specific extension (reserved as such by IS-101)
label=16
the phone is connected to the radio network. There is a path to the internal microphone, which is also connected to the radio transmitter. There is a path to the radio receiver, which is also connected to the internal loudspeaker. This allows the computer to record the sum of transmitted and received audio by selecting "receive mode".
loudspeaker computer i/p transmit stage
microphone →**
computer o/p →
receiver stage →**
label=17
the phone is connected to the radio system and there is a path to the internal loudspeaker and to the radio transmitter. This allows the computer to simultaneously play sound and send audio over the radio by selecting "transmit mode".
loudspeaker computer i/p transmit stage
microphone →
computer o/p →**
receiver stage →
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C.2.9  Receive data state +VRXp. 426

This action command causes the TA to get audio data from a source determined by the +VLS command, and send it to the computer. Once the datastream has started, any result codes will be embedded in the data and shielded using the normal <DLE> methods. The receive process is terminated when the computer sends any command to the TA, or by time-out of the inactivity timer. The command is write only.
Command Return
+VRXCONNECT
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C.2.10  Select compression method +VSMp. 426

This selects the voice compression method <n1>, the voice sampling rate <n2>, the silence compression sensitivity <n3>, and a parameter related to silence expansion <n4>. There are several choices of compression method. IS-101 does not specify methods, but here is a list of some usual compression methods:
Name Communications system
GSM/full-rateGSM
GSM/half-rateGSM
ADPCM/G.721DECT, CT2
ADPCM/G.723DECT, CT2
ADPCM/G.726DECT, CT2
ADPCM/G.727DECT, CT2
SIGNED PCMPOTS
Command Return
+VSM=<n1>,<n2>,<n3>,<n4>
+VSM? <n1>,<n2>,<n3>,<n4>
+VSM=?complex; refer IS-101
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C.2.11  DTMF and tone generation +VTSp. 427

This command allows the transmission of DTMF tones and arbitrary tones (see NOTE 1). These tones may be used (for example) when announcing the start of a recording period. The command is write only. In this profile of commands, this command does not operate in data or fax modes of operation (+FCLASS=0,1,2-7).
The string parameter of the command consists of combinations of the following separated by commas:
  1. <DTMF>. A single ASCII character in the set 0-9, #,*,A-D. This is interpreted as a single ACSII character whose duration is set by the +VTD command.
  2. [<tone1>,<tone2>,<duration>]. This is interpreted as a dual tone of frequencies <tone1> and <tone2>, lasting for a time <duration> (in 10 ms multiples).
  3. {<DTMF>,<duration>}. This is interpreted as a DTMF tone of different duration from that mandated by the +VTD command.
Command Return
+VTS=as above
+VTS=? (list of supported <tone1>s),(list of supported <tone2>s),(list of supported <duration>s)
Up

C.2.12  Tone duration +VTDp. 427

This refers to an integer <n> that defines the length of tones emitted as a result of the +VTS command. This does not affect the D command. A value different than zero causes a tone of duration <n>/10 seconds. The value zero causes a "manufacturer specific" value.
Command Return
+VTD=<n>
+VTD? <n>
+VTD=? (list of supported <n>s)
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C.2.13  Transmit data state +VTXp. 428

This action command causes the TA to receive audio data from the computer and send it to a destination determined by the +VLS command. Once the audio datastream has started, commands to the TA shall be embedded in the data stream, and shielded using the normal <DLE> methods. The transmit process is terminated by the use of embedded commands or by the time-out of an inactivity timer. It is recommended that the TA has a buffer to allow the TA to convert potentially bursty data from the computer into synchronous data for "transmission". The command is write only.
Command Return
+VTXCONNECT
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D  Bibliographyp. 429

Informative references:
  1. IrDA Serial Infrared Physical Layer Specification.
    IrDA Serial Infrared MAC and Link Protocol.
    IrDA Serial Infrared Link Access Protocol.
  2. PCCA STD-101 Annex I: Data Transmission Systems and Equipment - Serial Asynchronous Automatic Dialling and Control for Character Mode DCE on Wireless Data Services - Annex I: Command Extensions for Analog Cellular Data Modems.
  3. TIA IS-101 Facsimile Digital Interfaces - Voice Control Interim Standard for Asynchronous DCE.
  4. TIA-578-A Facsimile Digital Interfaces - Asynchronous Facsimile DCE Control Standard, Service Class 1.
  5. TIA-592 Facsimile Digital Interfaces - Asynchronous Facsimile DCE Control Standard, Service Class 2.
  6. TIA-617 Data Transmission Systems and Equipment - In-Band DCE Control.
  7. ITU-T Recommendation V.80: In-band DCE control and synchronous data modes for asynchronous DTE.
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