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M-980-02P bảng dữ liệu(PDF) 3 Page - Clare, Inc. |
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M-980-02P bảng dữ liệu(HTML) 3 Page - Clare, Inc. |
3 / 6 page Device Timing Time Value Significance t MD 40 ms A valid tone will always be detected if it is at least 40 ms long. t ID 40 ms @ -38 dBm Inter-tone gaps must be detected if greater than this duration. 85 ms @ -10 dBm t B 18 ms Drop-outs of valid tone of up to 18 ms will be ignored. Note: Application or removal of high level signals outside the must detect range may cause momentary detection, which may be filtered by time guarding the output. M-980-02 www.clare.com 3 Rev. 3 Signal Timing Call Progress Tone Detection Call progress tones are audible tones sent from switch- ing systems to calling parties to show the status of calls. Calling parties can identify the success of a call placed by what is heard after dialing. The type of tone used and its timing vary from system to system, and though intended for human ears these signals can pro- vide valuable information for automated calling sys- tems. The M-980-02 is a signal detector sensitive to the fre- quencies most often used for these progress tones. Electronic equipment monitoring the DETECT output of the M-980-02 can determine the nature of signals present by measuring their duty cycle. See Figure 4 for a diagram of a circuit that could be used to permit a microcomputer to directly monitor tones on the tele- phone line. Much of the character of the progress tones is in their duty cycle or cadence (sometimes referred to as interruption rate). This information, cou- pled with level and frequency indication from the M- 980-02, can be used to decide what progress tones have been encountered. Table 5 shows some call progress tones with on/off times; 0.25/0.25 being 250 ms on, 250 ms off on a repeating basis. For example, dial tones as shown in the table are usually “on” continuously and last until the first dial digit is received by the switching system. Line Busy, on the other hand, is turned off and on at a rate of 1 Hz with a 50% duty cycle, or an interruption rate of 60 times per minute (60 IPM). The tones can be dis- tinguished in this way. It should be noted that while such techniques will usu- ally be effective, there are some circumstances in which the M-980-02 cannot be accurately used. Examples include situations where ringback tone may be short or not even encountered. Ringback may be provided at ringing voltage frequency (20 or 30 Hz) with some harmonics and may not fall in the detect range, and speech or other strong noise may obscure tones making cadence measurement difficult. Detection of “answer” is most difficult for many rea- sons. One way to determine if a called party has answered is by looking for a short burst of DETECT indications without a cadence match (produced by a click and “hello” at the far end). Some applications will require special methods like speech detection, but most can be reliably handled with the M-980-02 and simple cadence measurement. As can be seen, the tones used for the same purpos- es in different systems may not be the same. Standards do exist and should be consulted for your particular application. In North America AT&Ts “Notes on the Network” or EIAs RS-464 PBX standard should be reviewed. In Europe tone plans may vary with locale, in which case the CEPT administration in each country must be consulted. Outside these areas, national PTT organizations can provide information on the systems within their borders. |
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Mô tả tương tự - M-980-02P |
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