rfc2833.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

      /ANSam: The modified answer tone with phase reversals (ANSam) [3]
           is a sinewave signal at 2100 +/- 1 Hz with phase reversals at
           intervals of 450 +/- 25 ms, amplitude-modulated by a sinewave
           at 15 +/- 0.1 Hz. This tone [10,8] is sent by modems [11] and
           faxes to disable echo suppressors.

      CNG: After dialing the called fax machine's telephone number (and
           before it answers), the calling Group III fax machine
           (optionally) begins sending a CalliNG tone (CNG) consisting
           of an interrupted tone of 1100 Hz. [9]

      CRdi: Capabilities Request (CRd), initiating side, [12] is a
           dual-tone signal with tones at 1375 Hz and 2002 Hz for 400
           ms, followed by a single tone at 1900 Hz for 100 ms. "This
           signal requests the remote station transition from telephony
           mode to an information transfer mode and requests the
           transmission of a capabilities list message by the remote
           station. In particular, CRdi is sent by the initiating
           station during the course of a call, or by the calling
           station at call establishment in response to a CRe or MRe."

      CRdr: CRdr is the response tone to CRdi (see above). It consists
           of a dual-tone signal with tones at 1529 Hz and 2225 Hz for
           400 ms, followed by a single tone at 1900 Hz for 100 ms.

      CRe: Capabilities Request (CRe) [12] is a dual-tone signal with
           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 requests the
           remote station transition from telephony mode to an
           information transfer mode and requests the transmission of a
           capabilities list message by the remote station. In
           particular, CRe is sent by an automatic 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.






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RFC 2833                         Tones                          May 2000


      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 tone at
           980 Hz for 100 ms. "This signal requests the remote station
           transition from telephony mode to an information transfer
           mode. signal ESi is sent by the initiating station."

      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 tone at
           1650 Hz for 100 ms. Same as ESi, but sent by the responding
           station.

      MRdi: Mode Request (MRd), initiating side, [12] is a dual-tone
           signal with tones at 1375 Hz and 2002 Hz for 400 ms followed
           by a single tone at 1150 Hz for 100 ms. "This signal requests
           the remote station transition from telephony mode to an
           information transfer mode and requests the transmission of a
           mode select message by the remote station. In particular,
           signal MRd is sent by the initiating station during the
           course of a call, or by the calling station at call
           establishment in response to an MRe." [12]

      MRdr: MRdr is the response tone to MRdi (see above). It consists
           of a dual-tone signal with tones at 1529 Hz and 2225 Hz for
           400 ms, followed by a single tone at 1150 Hz for 100 ms.

      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 at
           650 Hz for 100 ms. "This signal requests the remote station
           transition from telephony mode to an information transfer
           mode and requests the transmission of a mode select message
           by the remote station. In particular, signal MRe is sent by
           an automatic answering station at call establishment." [12]

      V.21: V.21 describes a 300 b/s full-duplex modem that employs
           frequency shift keying (FSK). It is used by Group 3 fax
           machines to exchange T.30 information. The calling transmits
           on channel 1 and receives on channel 2; the answering modem
           transmits on channel 2 and receives on channel 1. Each bit
           value has a distinct tone, so that V.21 signaling comprises a
           total of four distinct tones.











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RFC 2833                         Tones                          May 2000


   In summary, procedures in Table 2 are used.

           Procedure                      indications
           ___________________________________________________
           V.25 and V.8                   ANS
           V.25, echo canceller disabled  ANS, /ANS, ANS, /ANS
           V.8                            ANSam
           V.8, echo canceller disabled   /ANSam

      Table 2: Use of ANS, ANSam and /ANSam in V.x recommendations


           Event                    encoding (decimal)
           ___________________________________________________
           Answer tone (ANS)                        32
           /ANS                                     33
           ANSam                                    34
           /ANSam                                   35
           Calling tone (CNG)                       36
           V.21 channel 1, "0" bit                  37
           V.21 channel 1, "1" bit                  38
           V.21 channel 2, "0" bit                  39
           V.21 channel 2, "1" bit                  40
           CRdi                                     41
           CRdr                                     42
           CRe                                      43
           ESi                                      44
           ESr                                      45
           MRdi                                     46
           MRdr                                     47
           MRe                                      48
           CT                                       49

                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
   used. It defines the following standard tones that are heard by the
   caller:

      Dial tone: The exchange is ready to receive address information.






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RFC 2833                         Tones                          May 2000


      PABX internal dial tone: The PABX is ready to receive address
           information.

      Special dial tone: Same as dial tone, but the caller's line is
           subject to a specific condition, such as call diversion or a
           voice mail is available (e.g., "stutter dial tone").

      Second dial tone: The network has accepted the address
           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 calling
           signal (ringing) is being transmitted to the callee. This
           tone is also called "ringback".

      Special ringing tone: A special service, such as call forwarding
           or call waiting, is active at the called number.

      Busy tone: The called telephone number is busy.

      Congestion tone: Facilities necessary for the call are temporarily
           unavailable.

      Calling card service tone: The calling card service tone consists
           of 60 ms of the sum of 941 Hz and 1477 Hz tones (DTMF '#'),
           followed by 940 ms of 350 Hz and 440 Hz (U.S.  dial tone),
           decaying exponentially with a time constant of 200 ms.

      Special information tone: The callee cannot be reached, but the
           reason is neither "busy" nor "congestion". This tone should
           be used before all call failure announcements, for the
           benefit of automatic equipment.

      Comfort tone: The call is being processed. This tone may be used
           during long post-dial delays, e.g., in international
           connections.

      Hold tone: The caller has been placed on hold.

      Record tone: The caller has been connected to an automatic
           answering device and is requested to begin speaking.





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RFC 2833                         Tones                          May 2000


      Caller waiting tone: The called station is busy, but has call
           waiting service.

      Pay tone: The caller, at a payphone, is reminded to deposit
           additional coins.

      Positive indication tone: The supplementary service has been
           activated.

      Negative indication tone: The supplementary service could not be
           activated.

      Off-hook warning tone: The caller has left the instrument off-hook
           for an extended period of time.

   The following tones can be heard by either calling or called party
   during a conversation:

      Call waiting tone: Another party wants to reach the subscriber.

      Warning tone: The call is being recorded. This tone is not
           required in all jurisdictions.

      Intrusion tone: The call is being monitored, e.g., by an operator.

      CPE alerting signal: A tone used to alert a device to an arriving
           in-band FSK data transmission. A CPE alerting signal is a
           combined 2130 and 2750 Hz tone, both with tolerances of 0.5%
           and a duration of 80 to.  80 ms. The CPE alerting signal is
           used with ADSI services and Call Waiting ID services [14].

   The following tones are heard by operators:

      Payphone recognition tone: The person making the call or being
           called is using a payphone (and thus it is ill-advised to
           allow collect calls to such a person).















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RFC 2833                         Tones                          May 2000


          Event                      encoding (decimal)
          _____________________________________________
          Off Hook                                  64
          On Hook                                   65
          Dial tone                                 66
          PABX internal dial tone                   67
          Special dial tone                         68
          Second dial tone                          69
          Ringing tone                              70
          Special ringing tone                      71
          Busy tone                                 72
          Congestion tone                           73
          Special information tone                  74
          Comfort tone                              75
          Hold tone                                 76
          Record tone                               77
          Caller waiting tone                       78
          Call waiting tone                         79
          Pay tone                                  80
          Positive indication tone                  81
          Negative indication tone                  82
          Warning tone                              83
          Intrusion tone                            84
          Calling card service tone                 85
          Payphone recognition tone                 86
          CPE alerting signal (CAS)                 87
          Off-hook warning tone                     88
          Ring                                      89

                   Table 4: E.182 line events

3.13 Extended Line Events

   Table 5 summarizes country-specific events and tones that can appear
   on a subscriber line.

3.14 Trunk Events