draft-ietf-avt-tones-03.txt   draft-ietf-avt-tones-04.txt 
Internet Engineering Task Force AVT WG Internet Engineering Task Force AVT WG
Internet Draft Schulzrinne/Petrack Internet Draft Schulzrinne/Petrack
draft-ietf-avt-tones-03.txt Columbia U./MetaTel draft-ietf-avt-tones-04.txt Columbia U./MetaTel
November 28, 1999 December 9, 1999
Expires: May 2000 Expires: May 2000
RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
STATUS OF THIS MEMO STATUS OF THIS MEMO
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
skipping to change at page 12, line 44 skipping to change at page 12, line 44
CRe: Capabilities Request (CRe) [12] is a dual-tone signal with CRe: Capabilities Request (CRe) [12] is a dual-tone signal with
tones at tones at 1375 Hz and 2002 Hz for 400 ms, followed tones at tones at 1375 Hz and 2002 Hz for 400 ms, followed
by a single tone at 400 Hz for 100 ms. "This signal by a single tone at 400 Hz for 100 ms. "This signal
requests the remote station transition from telephony mode requests the remote station transition from telephony mode
to an information transfer mode and requests the to an information transfer mode and requests the
transmission of a capabilities list message by the remote transmission of a capabilities list message by the remote
station. In particular, CRe is sent by an automatic station. In particular, CRe is sent by an automatic
answering station at call establishment." answering station at call establishment."
CT: "The calling tone [8] consists of a series of interrupted
bursts of binary 1 signal or 1300 Hz, on for a duration of
not less than 0.5 s and not more than 0.7 s and off for a
duration of not less than 1.5 s and not more than 2.0 s."
Modems not starting with the V.8 call initiation tone often
use this tone.
ESi: Escape Signal (ESi) [12] is a dual-tone signal with tones ESi: Escape Signal (ESi) [12] is a dual-tone signal with tones
at 1375 Hz and 2002 Hz for 400 ms, followed by a single at 1375 Hz and 2002 Hz for 400 ms, followed by a single
tone at 980 Hz for 100 ms. "This signal requests the remote tone at 980 Hz for 100 ms. "This signal requests the remote
station transition from telephony mode to an information station transition from telephony mode to an information
transfer mode. signal ESi is sent by the initiating transfer mode. signal ESi is sent by the initiating
station." station."
ESr: Escape Signal (ESr) [12] is a dual-tone signal with tones ESr: Escape Signal (ESr) [12] is a dual-tone signal with tones
at 1529 Hz and 2225 Hz for 400 ms, followed by a single at 1529 Hz and 2225 Hz for 400 ms, followed by a single
tone at 1650 Hz for 100 ms. Same as ESi, but sent by the tone at 1650 Hz for 100 ms. Same as ESi, but sent by the
skipping to change at page 13, line 30 skipping to change at page 13, line 37
MRe: Mode Request (MRe) [12] is a dual-tone signal with tones at MRe: Mode Request (MRe) [12] is a dual-tone signal with tones at
1375 Hz and 2002 Hz for 400 ms, followed by a single tone 1375 Hz and 2002 Hz for 400 ms, followed by a single tone
at 650 Hz for 100 ms. "This signal requests the remote at 650 Hz for 100 ms. "This signal requests the remote
station transition from telephony mode to an information station transition from telephony mode to an information
transfer mode and requests the transmission of a mode transfer mode and requests the transmission of a mode
select message by the remote station. In particular, signal select message by the remote station. In particular, signal
MRe is sent by an automatic answering station at call MRe is sent by an automatic answering station at call
establishment." [12] establishment." [12]
V.21: V.21 describes a 300 b/s full-duplex modem that employs V.21: V.21 describes a 300 b/s full-duplex modem that employs
frequency shift keying (FSK). It is now used by Group 3 fax frequency shift keying (FSK). It is used by Group 3 fax
machines to exchange T.30 information. The calling machines to exchange T.30 information. The calling
transmits on channel 1 and receives on channel 2; the transmits on channel 1 and receives on channel 2; the
answering modem transmits on channel 2 and receives on answering modem transmits on channel 2 and receives on
channel 1. Each bit value has a distinct tone, so that V.21 channel 1. Each bit value has a distinct tone, so that V.21
signaling comprises a total of four distinct tones. signaling comprises a total of four distinct tones.
In summary, procedures in Table 2 are used. In summary, procedures in Table 2 are used.
3.12 Line Events
Table 4 summarizes the events and tones that can appear on a
subscriber line.
Procedure indications Procedure indications
________________________________________________________ ________________________________________________________
V.25 and V.8 ANS, ANS, ... V.25 and V.8 ANS, ANS, ...
V.25, echo canceller disabled ANS, /ANS, ANS, /ANS V.25, echo canceller disabled ANS, /ANS, ANS, /ANS
V.8 ANSam, ANSam, ... V.8 ANSam, ANSam, ...
V.8, echo canceller disabled ANSam, /ANSam, ANSam, ... V.8, echo canceller disabled ANSam, /ANSam, ANSam, ...
Table 2: Use of ANS, ANSam and /ANSam in V.x recommendations Table 2: Use of ANS, ANSam and /ANSam in V.x recommendations
Event encoding (decimal)
___________________________________________ Event____________________encoding_(decimal)
Answer tone (ANS) 32 Answer tone (ANS) 32
/ANS 33 /ANS 33
ANSam 34 ANSam 34
/ANSam 35 /ANSam 35
Calling tone (CNG) 36 Calling tone (CNG) 36
V.21 channel 1, "0" bit 37 V.21 channel 1, "0" bit 37
V.21 channel 1, "1" bit 38 V.21 channel 1, "1" bit 38
V.21 channel 2, "0" bit 39 V.21 channel 2, "0" bit 39
V.21 channel 2, "1" bit 40 V.21 channel 2, "1" bit 40
CRd 41 CRd 41
CRe 42 CRe 42
ESi 43 ESi 43
ESr 44 ESr 44
MRd 45 MRd 45
MRe 46 MRe 46
CT 47
Table 3: Data and fax named events Table 3: Data and fax named events
3.12 Line Events
Table 4 summarizes the events and tones that can appear on a
subscriber line.
ITU Recommendation E.182 [13] defines when certain tones should be ITU Recommendation E.182 [13] defines when certain tones should be
used. It defines the following standard tones that are heard by the used. It defines the following standard tones that are heard by the
caller: caller:
Dial tone: The exchange is ready to receive address information. Dial tone: The exchange is ready to receive address information.
PABX internal dial tone: The PABX is ready to receive address PABX internal dial tone: The PABX is ready to receive address
information. information.
Special dial tone: Same as dial tone, but the caller's line is Special dial tone: Same as dial tone, but the caller's line is
subject to a specific condition, such as call diversion or subject to a specific condition, such as call diversion or
a voice mail is available (e.g., "stutter dial tone"). a voice mail is available (e.g., "stutter dial tone").
Second dial tone: The network has accepted the address Second dial tone: The network has accepted the address
information, but additional information is required. information, but additional information is required.
Ring: This named signal event causes the recipient to generate
an alerting signal ("ring"). The actual tone or other
indication used to render this named event is left up to
the receiver. (This differs from the ringing tone, below,
heard by the caller
Ringing tone: The call has been placed to the callee and a Ringing tone: The call has been placed to the callee and a
calling signal (ringing) is being transmitted to the calling signal (ringing) is being transmitted to the
callee. callee. This tone is also called "ringback".
Special ringing tone: A special service, such as call forwarding Special ringing tone: A special service, such as call forwarding
or call waiting, is active at the called number. or call waiting, is active at the called number.
Busy tone: The called telephone number is busy. Busy tone: The called telephone number is busy.
Congestion tone: Facilities necessary for the call are Congestion tone: Facilities necessary for the call are
temporarily unavailable. temporarily unavailable.
Calling card service tone: The calling card service tone Calling card service tone: The calling card service tone
skipping to change at page 16, line 21 skipping to change at page 16, line 34
tolerances of 0.5% and a duration of 80 to. 80 ms. The CPE tolerances of 0.5% and a duration of 80 to. 80 ms. The CPE
alerting signal is used with ADSI services and Call Waiting alerting signal is used with ADSI services and Call Waiting
ID services [14]. ID services [14].
The following tones are heard by operators: The following tones are heard by operators:
Payphone recognition tone: The person making the call or being Payphone recognition tone: The person making the call or being
called is using a payphone (and thus it is ill-advised to called is using a payphone (and thus it is ill-advised to
allow collect calls to such a person). allow collect calls to such a person).
3.13 Extended Line Events
Table 5 summarizes country-specific events and tones that can appear
on a subscriber line.
3.14 Trunk Events
Table 6 summarizes the events and tones that can appear on a trunk.
Note that trunk can also carry line events (Section 3.12), as MF
signaling does not include backward signals [15].
ABCD transitional: 4-bit signaling used by digital trunks. For
N-state signaling, the first N values are used.
The T1 ESF (extended super frame format) allows 2, 4, and
16 state signalling bit options. These signalling bits are
Event encoding (decimal) Event encoding (decimal)
_____________________________________________ _____________________________________________
Off Hook 64 Off Hook 64
On Hook 65 On Hook 65
Dial tone 66 Dial tone 66
PABX internal dial tone 67 PABX internal dial tone 67
Special dial tone 68 Special dial tone 68
Second dial tone 69 Second dial tone 69
Ringing tone 70 Ringing tone 70
Special ringing tone 71 Special ringing tone 71
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Call waiting tone 79 Call waiting tone 79
Pay tone 80 Pay tone 80
Positive indication tone 81 Positive indication tone 81
Negative indication tone 82 Negative indication tone 82
Warning tone 83 Warning tone 83
Intrusion tone 84 Intrusion tone 84
Calling card service tone 85 Calling card service tone 85
Payphone recognition tone 86 Payphone recognition tone 86
CPE alerting signal (CAS) 87 CPE alerting signal (CAS) 87
Off-hook warning tone 88 Off-hook warning tone 88
Ring 89
Table 4: E.182 line events Table 4: E.182 line events
3.13 Extended Line Events named A, B, C, and D. Signalling information is sent as
robbed bits in frames 6, 12, 18, and 24 when using ESF T1
framing. A D4 superframe only transmits 4-state signalling
with A and B bits. On the CEPT E1 frame, all signalling is
carried in timeslot 16, and two channels of 16-state (ABCD)
signalling are sent per frame.
Table 5 summarizes country-specific events and tones that can appear Since this information is a state rather than a changing
on a subscriber line. signal, implementations SHOULD use the following triple-
redundancy mechanism, similar to the one specified in ITU-T
Rec. I.366.2 [16], Annex L. At the time of a transition,
the same ABCD information is sent 3 times at an interval of
5 ms. If another transition occurs during this time, then
this continues. After a period of no change, the ABCD
information is sent every 5 seconds.
Event encoding (decimal) Event encoding (decimal)
___________________________________________________ ___________________________________________________
Acceptance tone 96 Acceptance tone 96
Confirmation tone 97 Confirmation tone 97
Dial tone, recall 98 Dial tone, recall 98
End of three party service tone 99 End of three party service tone 99
Facilities tone 100 Facilities tone 100
Line lockout tone 101 Line lockout tone 101
Number unobtainable tone 102 Number unobtainable tone 102
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Queue tone 106 Queue tone 106
Refusal tone 107 Refusal tone 107
Route tone 108 Route tone 108
Valid tone 109 Valid tone 109
Waiting tone 110 Waiting tone 110
Warning tone (end of period) 111 Warning tone (end of period) 111
Warning Tone (PIP tone) 112 Warning Tone (PIP tone) 112
Table 5: Country-specific Line events Table 5: Country-specific Line events
3.14 Trunk Events Wink: A brief transition, typically 120-290 ms, from on-hook
(unseized) to off-hook (seized) and back to onhook, used by
the incoming exchange to signal that the call address
signaling can proceed.
Table 6 summarizes the events and tones that can appear on a trunk. Incoming seizure: Incoming indication of call attempt (off-
Note that trunk can also carry line events (Section 3.12), as MF hook).
signaling does not include backward signals [15].
ABCD transitional: 4-bit signaling used by digital trunks. For Return seizure: Seizure by answering exchange, in response to
N-state signaling, the first N values are used. outgoing seizure. [NOTE: Not clear why the difference here,
but not for Unseize. Should probably be just Seizure.]
The T1 ESF (extended super frame format) allows 2, 4, and Unseize circuit: Transition of circuit from off-hook to on-hook
16 state signalling bit options. These signalling bits are at the end of a call.
named A, B, C, and D. Signalling information is sent as
robbed bits in frames 6, 12, 18, and 24 when using ESF T1 Wink off: A brief transition, typically 100-350 ms, from off-
framing. A D4 superframe only transmits 4-state signalling hook (seized) to on-hook (unseized) and back to off-hook
with A and B bits. On the CEPT E1 frame, all signalling is (seized). Used in operator services trunks.
carried in timeslot 16, and two channels of 16-state (ABCD)
signalling are sent per frame. Continuity tone send: A tone of 2010 Hz.
Continuity tone detect: A tone of 2010 Hz.
Continuity test send: A tone of 1780 Hz is sent by the calling
exchange. If received by the called exchange, it returns a
Event encoding (decimal) Event encoding (decimal)
__________________________________________________ __________________________________________________
MF 0... 9 128... 137 MF 0... 9 128... 137
MF K0 or KP (start-of-pulsing) 138 MF K0 or KP (start-of-pulsing) 138
MF K1 139 MF K1 139
MF K2 140 MF K2 140
MF S0 to ST (end-of-pulsing) 141 MF S0 to ST (end-of-pulsing) 141
MF S1... S3 142... 143 MF S1... S3 142... 143
ABCD signaling (see below) 144... 159 ABCD signaling (see below) 144... 159
Wink 160 Wink 160
skipping to change at page 18, line 30 skipping to change at page 19, line 29
Default continuity tone 166 Default continuity tone 166
Continuity tone (single tone) 167 Continuity tone (single tone) 167
Continuity test send 168 Continuity test send 168
Continuity verified 170 Continuity verified 170
Loopback 171 Loopback 171
Old milliwatt tone (1000 Hz) 172 Old milliwatt tone (1000 Hz) 172
New milliwatt tone (1004 Hz) 173 New milliwatt tone (1004 Hz) 173
Table 6: Trunk events Table 6: Trunk events
Since this information is a state rather than a changing
signal, implementations SHOULD use the following triple-
redundancy mechanism, similar to the one specified in ITU-T
Rec. I.366.2 [16], Annex L. At the time of a transition,
the same ABCD information is sent 3 times at an interval of
5 ms. If another transition occurs during this time, then
this continues. After a period of no change, the ABCD
information is sent every 5 seconds.
Wink: A brief transition, typically 120-290 ms, from on-hook
(unseized) to off-hook (seized) and back to onhook, used by
the incoming exchange to signal that the call address
signaling can proceed.
Incoming seizure: Incoming indication of call attempt (off-
hook).
Return seizure: Seizure by answering exchange, in response to
outgoing seizure. [NOTE: Not clear why the difference here,
but not for Unseize. Should probably be just Seizure.]
Unseize circuit: Transition of circuit from off-hook to on-hook
at the end of a call.
Wink off: A brief transition, typically 100-350 ms, from off-
hook (seized) to on-hook (unseized) and back to off-hook
(seized). Used in operator services trunks.
Continuity tone send: A tone of 2010 Hz.
Continuity tone detect: A tone of 2010 Hz.
Continuity test send: A tone of 1780 Hz is sent by the calling
exchange. If received by the called exchange, it returns a
"continuity verified" tone. "continuity verified" tone.
Continuity verified: A tone of 2010 Hz. This is a response tone, Continuity verified: A tone of 2010 Hz. This is a response tone,
used in dual-tone procedures. used in dual-tone procedures.
4 RTP Payload Format for Telephony Tones 4 RTP Payload Format for Telephony Tones
4.1 Introduction 4.1 Introduction
As an alternative to describing tones and events by name, as As an alternative to describing tones and events by name, as
skipping to change at page 20, line 23 skipping to change at page 20, line 38
4.2 Examples of Common Telephone Tone Signals 4.2 Examples of Common Telephone Tone Signals
As an aid to the implementor, Table 7 summarizes some common tones. As an aid to the implementor, Table 7 summarizes some common tones.
The rows labeled "ITU ..." refer to the general recommendation of The rows labeled "ITU ..." refer to the general recommendation of
Recommendation E.180 [18]. Note that there are no specific guidelines Recommendation E.180 [18]. Note that there are no specific guidelines
for these tones. In the table, the symbol "+" indicates addition of for these tones. In the table, the symbol "+" indicates addition of
the tones, without modulation, while "*" indicates amplitude the tones, without modulation, while "*" indicates amplitude
modulation. The meaning of some of the tones is described in Section modulation. The meaning of some of the tones is described in Section
3.12 or Section 3.11 (for V.21). 3.12 or Section 3.11 (for V.21).
4.3 Use of RTP Header Fields
Timestamp: The RTP timestamp reflects the measurement point for
the current packet. The event duration described in Section
3.5 extends forwards from that time.
4.4 Payload Format
Based on the characteristics described above, this document defines
an RTP payload format called "tone" that can represent tones
consisting of one or more frequencies. (The corresponding MIME type
is "audio/tone".) The default timestamp rate is 8,000 Hz, but other
rates may be defined. Note that the timestamp rate does not affect
the interpretation of the frequency, just the durations.
Tone name frequency on period off period Tone name frequency on period off period
______________________________________________________ ______________________________________________________
CNG 1100 0.5 3.0 CNG 1100 0.5 3.0
V.25 CT 1300 0.5 2.0
CED 2100 3.3 -- CED 2100 3.3 --
ANS 2100 3.3 -- ANS 2100 3.3 --
ANSam 2100*15 3.3 -- ANSam 2100*15 3.3 --
V.21 "0" bit, ch. 1 1180 0.033 V.21 "0" bit, ch. 1 1180 0.033
V.21 "1" bit, ch. 1 980 0.033 V.21 "1" bit, ch. 1 980 0.033
V.21 "0" bit, ch. 2 1850 0.033 V.21 "0" bit, ch. 2 1850 0.033
V.21_"1"_bit,_ch._2________1650______0.033____________ V.21_"1"_bit,_ch._2________1650______0.033____________
ITU dial tone 425 -- -- ITU dial tone 425 -- --
U.S. dial tone 350+440 -- -- U.S. dial tone 350+440 -- --
______________________________________________________ ______________________________________________________
ITU ringing tone 425 0.67--1.5 3--5 ITU ringing tone 425 0.67--1.5 3--5
U.S._ringing_tone_______440+480________2.0_________4.0 U.S._ringing_tone_______440+480________2.0_________4.0
ITU busy tone 425 ITU busy tone 425
U.S. busy tone 480+620 0.5 0.5 U.S. busy tone 480+620 0.5 0.5
______________________________________________________ ______________________________________________________
ITU congestion tone 425 ITU congestion tone 425
U.S. congestion tone 480+620 0.25 0.25 U.S. congestion tone 480+620 0.25 0.25
Table 7: Examples of telephony tones Table 7: Examples of telephony tones
4.3 Use of RTP Header Fields
Timestamp: The RTP timestamp reflects the measurement point for
the current packet. The event duration described in Section
3.5 extends forwards from that time.
4.4 Payload Format
Based on the characteristics described above, this document defines
an RTP payload format called "tone" that can represent tones
consisting of one or more frequencies. (The corresponding MIME type
is "audio/tone".) The default timestamp rate is 8,000 Hz, but other
rates may be defined. Note that the timestamp rate does not affect
the interpretation of the frequency, just the durations.
In accordance with current practice, this payload format does not In accordance with current practice, this payload format does not
have a static payload type number, but uses a RTP payload type number have a static payload type number, but uses a RTP payload type number
established dynamically and out-of-band. established dynamically and out-of-band.
It is shown in Fig. 2. It is shown in Fig. 2.
The payload contains the following fields:
modulation: The modulation frequency, in Hz. The field is a 9-
bit unsigned integer, allowing modulation frequencies up to
511 Hz. If there is no modulation, this field has a value
of zero.
T: If the "T" bit is set (one), the modulation frequency is to
be divided by three. Otherwise, the modulation frequency is
taken as is.
This bit allows frequencies accurate to 1/3 Hz, since
modulation frequencies such as 16 2/3 Hz are in
practical use.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| modulation |T| volume | duration | | modulation |T| volume | duration |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| frequency |R R R R| frequency | |R R R R| frequency |R R R R| frequency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| frequency |R R R R| frequency | |R R R R| frequency |R R R R| frequency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...... ......
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| frequency |R R R R| frequency | |R R R R| frequency |R R R R| frequency |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Payload format for tones Figure 2: Payload format for tones
The payload contains the following fields:
modulation: The modulation frequency, in Hz. The field is a 9-
bit unsigned integer, allowing modulation frequencies up to
511 Hz. If there is no modulation, this field has a value
of zero.
T: If the "T" bit is set (one), the modulation frequency is to
be divided by three. Otherwise, the modulation frequency is
taken as is.
This bit allows frequencies accurate to 1/3 Hz, since
modulation frequencies such as 16 2/3 Hz are in
practical use.
volume: The power level of the tone, expressed in dBm0 after volume: The power level of the tone, expressed in dBm0 after
dropping the sign, with range from 0 to -63 dBm0. (Note: A dropping the sign, with range from 0 to -63 dBm0. (Note: A
preferred level range for digital tone generators is -8 preferred level range for digital tone generators is -8
dBm0 to -3 dBm0.) dBm0 to -3 dBm0.)
duration: The duration of the tone, measured in timestamp units. duration: The duration of the tone, measured in timestamp units.
The tone begins at the instant identified by the RTP The tone begins at the instant identified by the RTP
timestamp and lasts for the duration value. timestamp and lasts for the duration value.
The definition of duration corresponds to that for The definition of duration corresponds to that for
skipping to change at page 23, line 39 skipping to change at page 24, line 4
implementation. implementation.
The "rate" parameter describes the sampling rate, in Hertz. The "rate" parameter describes the sampling rate, in Hertz.
The number is written as a floating point number or as an The number is written as a floating point number or as an
integer. If omitted, the default value is 8000 Hz. integer. If omitted, the default value is 8000 Hz.
Encoding considerations: This type is only defined for transfer Encoding considerations: This type is only defined for transfer
via RTP [1]. via RTP [1].
Security considerations: See the "Security Considerations" Security considerations: See the "Security Considerations"
(Section 7) section in this document.
Interoperability considerations: none
Published specification: This document.
Applications which use this media: The telephone-event audio
subtype supports the transport of events occuring in
telephone systems over the Internet.
Additional information:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| V |P|X| CC |M| PT | sequence number | | V |P|X| CC |M| PT | sequence number |
| 2 |0|0| 0 |0| 96 | 31 | | 2 |0|0| 0 |0| 96 | 31 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| timestamp | | timestamp |
| 48000 | | 48000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| synchronization source (SSRC) identifier | | synchronization source (SSRC) identifier |
skipping to change at page 24, line 43 skipping to change at page 24, line 42
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| modulation=0 |0| volume=5 | duration=12000 | | modulation=0 |0| volume=5 | duration=12000 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| frequency=440 |0 0 0 0| frequency=480 | |0 0 0 0| frequency=440 |0 0 0 0| frequency=480 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Combining tones and events in a single RTP packet Figure 3: Combining tones and events in a single RTP packet
(Section 7) section in this document.
Interoperability considerations: none
Published specification: This document.
Applications which use this media: The telephone-event audio
subtype supports the transport of events occuring in
telephone systems over the Internet.
Additional information:
1. Magic number(s): N/A 1. Magic number(s): N/A
2. File extension(s): N/A 2. File extension(s): N/A
3. Macintosh file type code: N/A 3. Macintosh file type code: N/A
6.2 audio/tone 6.2 audio/tone
MIME media type name: audio MIME media type name: audio
skipping to change at page 26, line 27 skipping to change at page 26, line 40
has closed. has closed.
The meaning of new events MUST be documented either as an RFC or an The meaning of new events MUST be documented either as an RFC or an
equivalent standards document produced by another standardization equivalent standards document produced by another standardization
body, such as ITU-T. body, such as ITU-T.
9 Acknowledgements 9 Acknowledgements
The suggestions of the Megaco working group are gratefully The suggestions of the Megaco working group are gratefully
acknowledged. Detailed advice and comments were provided by Fred acknowledged. Detailed advice and comments were provided by Fred
Burg, Steve Casner, Fatih Erdin, Mike Fox, Terry Lyons, Colin Perkins Burg, Steve Casner, Fatih Erdin, Bill Foster, Mike Fox, Gunnar
and Steve Magnell. Hellstrom, Terry Lyons, Colin Perkins and Steve Magnell.
10 Authors 10 Authors
Henning Schulzrinne Henning Schulzrinne
Dept. of Computer Science Dept. of Computer Science
Columbia University Columbia University
1214 Amsterdam Avenue 1214 Amsterdam Avenue
New York, NY 10027 New York, NY 10027
USA USA
electronic mail: schulzrinne@cs.columbia.edu electronic mail: schulzrinne@cs.columbia.edu
 End of changes. 

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