Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: mark kallas Newsgroups: comp.dcom.telecom Subject: Re: Touchtone Detection Question Message-ID: <10478@accuvax.nwu.edu> Date: 5 Aug 90 14:36:15 GMT Sender: news@accuvax.nwu.edu Organization: DSC Communications, Plano Tx. Lines: 38 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 543, Message 6 of 9 In article <10356@accuvax.nwu.edu> gmc@wisvr.att.com (Glenn M Cooley) writes: >Some/most systems I've come across which have you enter data through >TT are able to correctly decode my input, long pulses, short pulses, >quick pulses, Bell phones, non-Bell phones. Other systems, such as >various answering machines are very fickle. I have to master a >certain pressing technique and can only use certain phones (non-PBX >Bell phones are the best) and still need to use several tries. >Why/comments/etc? Most of the time answering machines and some voice mail systems require a two or three second holding time before they will decode an incoming digit. If I remember right minimum duration for DFMT (TT) is 100 msec, I would guess the average persons button pushing is 200-500 msec. This means the dialer has to hold the button down "a long time". A second reason PBX may not work is if they are digital instruments. Digital phones do not have a DTMF send in them, so when a buttom is pressed the PBX "sees" the botton and then send a digit to whoever your conected to. These tones are saved in digital form and used to send digits to the cental office. Most of the time these digits are only sent for 100 msec. A third reason some regular (cheap) phones will not sometimes is due to reverse current. When a phone being dialed, it gets it power, -48 volts from the central office. Many central offices will reverse polarity, making + 48 volts, after your call is answered. This is most often used to tell when billing sould start. On the other hand, if the phone you using to dial out on will only let you send digits when it has -48 volts, it won't after the call is answered. UUCP : texbell!digi!mkallas Internet: mkallas@digi.lonestar.org