There was an extensive user discussion of DTMF tone length and pauses in September and October of 2010. I was unable to respond to that thread because it is closed now, but is still accessible by archives.
AS many other iPhone users have stated in many forum messages, the iPhone 3, #G, #GS, and 4 all have a serious problem with DTMF tone length and speed. Some users on the forum have blamed ATT, but I never had this problem with other non-iPhone phones on ATT (or with Cingular before the buyout) and others are now having this problem now on Verizon as well.
The iPhone (3G, 3GS, and 4) all emit DTMF tones v e r y , v e r y slowly. So slowly in fact, that users often cannot use stings of stored access numbers, followed by access codes, followed by recipient phone number for international calling cards or business-related conference calls. The iPhone user frequently receives a voice error message from the calling card system stating that the access code is invalid, despite the correct number being stored, along with proper "," pauses. The DTMF tones are also sometimes too long, or too brief, and/or with inconsistent delays between the tones, creating errors in the DTMF data transmitted, hence the "invalid access code" or "incorrect phone number" being dialed. I was able to intermittently get the iPhone to work on international calling cards, by playing with the number of pauses "," inserted between access phone numbers, access codes, and recipient numbers, but success was infrequent and not consistent. Then I updated to the most recent firmware version for my iPhone 3G this past weekend, and now the problem is even worse: the tones sound weaker, sound more computer-generated (like a bad wav file of what was supposed to be a DTMF tone), are shorter in tone duration usually, and occasionally with a few very long prolonged DTMF tones, like the iPhone is locking up for a moment during the tone generation. But the main change is that the slow sequence of generated tones is EVEN SLOWER with the new iPhone firmware update. A number string that my LG Env3 cranks out in 3 seconds takes about 30 or more seconds, with each tone separated from the next by painfully too much time intervals between them.
My Verizon LG Env3 always works in this function with international calling cards 100% of the time, with rapid-fire DTMF tones generated from my saved nnumber strings from the contact list and no errors.
These very slow iPhone DTMF tones are not apparent to the casual user, because when numbers are entered manually, you do not hear the tones. However, when a string of tones is necessary to interface with an international calling card or to enter or set up a conference call, the very slow tones are heard in the earpiece and are 5 - 10 times slower than with any other "real" cell phone. ALL other phones by LG, Motorola, Nokia, etc. that I have used for these purposes with ATT or Verizon always generate rapid-fire DTMF tones, even when evoked from the Contact List memory, even when a long string of access phone number, followed by access code and recipient phone number are used.
Why can't Apple get this right. The iPhone is a great iPod, camera, computer, PDA, and web browser. But this inherent defect makes it a very weak business phone. PLEASE fix this !! Apple has not addressed the problem with ANY updates, even the most recent one.
I found a temporary work-around with a free APP called, "Phonecard". It allows calling card or conference call access numbers and codes to be stored, then brings up the contact list, and sequences the numbers correctly. The DTMF tones are still slower than with any other phone, but at least it works using this APP.
Apple, if you follow this forum. This is a real problem, a glaring deficiency, and if you want my company's comtinued business in the future, please do something to correct the slow, weak, inadequate DTMF tone gererator in your iPhones. Otherwise, the Droid X and Droids Incredible seem to handle this task quite well.
