Path: utzoo!utgpu!watmath!clyde!att!osu-cis!killer!vector!nobody From: swlabs!jack@uunet.UU.NET (Jack Bonn) Newsgroups: comp.dcom.telecom Subject: Re: DTMF vs. Touch-Tone Message-ID: Date: 22 Dec 88 11:03:44 GMT Sender: chip@vector.UUCP Lines: 34 Approved: telecom-request@vector.uucp X-Submissions-To: telecom@bu-cs.bu.edu X-Administrivia-To: telecom-request@vector.uucp X-TELECOM-Digest: volume 8, issue 208, message 1 Frank Prindle (prindle@NADC.ARPA) writes: > I'm curious when the term DTMF (Dual Tone Multi Frequency) became synonymous > with Touch Tone. As I recall, DTMF once designated the set of dual-tone > frequencies used for in-band signaling on long distance trunks, which used > a completely different set of tones than Touch Tone, and was always generated > within the CO, not by any phone set (well, except for the "blue boxes"). The inter-office tone-based signaling system that was (is?) used in the US is referred to as MF signaling. It uses 2 out of 6 (2/6) tones to convey register signaling information between central offices. It also uses a 2600 Hz in-band supervisory signal on idle (the famous Cap'n Crunch tone) and was non-compelled and operated on a link-by-link (rather than an end-to-end) basis. Although MF's in-band supervisory signaling was vulnerable to fraud, its link-by-link, non-compelled nature gave it some definite speed advantages over R2 which was the prevalent trunk signaling system in most of the rest of the world at the same time. R2 uses end-to-end compelled signaling (where each tone is acknowledged) and is notoriously slow. I think that an international version of MF was called R1 in the CCITT books. DTMF uses 7 or 8 frequencies, depending on the application, and is used primarily as a subscriber-line signaling system (although it also includes signaling between the CO and DID PABXs). Correct me if I'm wrong, but I don't think that DTMF was ever referred to as MF or the other way around. ---- Jack Bonn, <> Software Labs, Ltd, Box 451, Easton CT 06612 uunet!swlabs!jack (UUCP) jack%swlabs.uucp@uunet.uu.net (INTERNET)