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I wrote a Java program to mimic the sounds to dial phone numbers, it works fine except when it comes to phone cards, it needs to dial a local number first (no problem, it successfully connects to a local number), then it needs to enter the card number, problem is the other end won't accept the generated sounds for the card numbers, it only takes hand entered card numbers (I had to physically enter the digits on the phone keypad by hand), why can it take phone number by sounds while not being able to take sounds for the card numbers ? Anyone familiar with the phone system can answer this question ? Anything I can do so my Java program will be able to mimic the entering of the card numbers ?

Vadim Kotov
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Frank
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  • How are you generating the DTMF tones? My first guess is that the system accepting the calling card entry has a narrower frequency tolerance band than your local phone carrier. – Michael Petrotta Nov 07 '09 at 20:06
  • Nice guess, I suspect it only takes an electric signal generated by pressing the keypad while ignoring the sounds it creates, but since I am no expert on the phone systems, I need some advice from someone who really knows about it. – Frank Nov 07 '09 at 20:35
  • No, it's the tone (or two tones; look up DTMF) that matters. – Michael Petrotta Nov 07 '09 at 20:45
  • http://en.wikipedia.org/wiki/Dual-tone_multi-frequency – Michael Petrotta Nov 07 '09 at 20:45
  • My Java program play some *.wav sound files to mimic the dialing, how can I convert the sounds on the website you mentioned above such as "Dtmf2.ogg" to a *.wav file to it can playback ? – Frank Nov 07 '09 at 21:27
  • Oh, I just found a site that will generate the *.wav sounds for me, and I have a choice of mono 44100 Hz, 16000 HZ or 8000 HZ, which is the best ? Or does it matter ? – Frank Nov 07 '09 at 21:40
  • I'm not an expert, but I doubt it matters. POTS (analog) lines have a typical bandwidth of 3KHz. – Michael Petrotta Nov 08 '09 at 05:37

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Yes, "it's the tone (or two tones; look up DTMF) that matters", I turned up the speaker volume and now it works.

Frank
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