Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!killer!vector!nobody From: westmark!dave@rutgers.edu (Dave Levenson) Newsgroups: comp.dcom.telecom Subject: Re: DTMF vs. Touch-Tone Message-ID: Date: 26 Dec 88 14:11:51 GMT Sender: chip@vector.UUCP Lines: 35 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 209, message 5 In article , swlabs!jack@uunet.UU.NET (Jack Bonn) writes: (in reply to Frank Prindle's question regarding DTMF vs MF) ... > 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 ... Perhaps I'm nit-picking, but the MF singaling includes only the 2/6 tone set that conveys addressing information. The in-band 2600 Hz supervisory signaling (called SF) was often used on the same trunks that also used MF, but the two are not related. MF addressing is also used on trunks with E&M and other kinds of out-of-band supervisory signaling. SF supervision was also used on trunks where non-MF addressing was used. I can remember (the 1960's) when electromechanical switches sent dial-pulse signaling over inter-office trunks. If SF supervision was used on the trunks, the 2600 Hz supervisory signal was pulsed on and off to transmit the pulses. No MF was used. The "blue box" only enabled its user to commit toll-fraud on trunks where both SF and MF were used. There are very few such circuits still in use: As the toll networks become digital, supervision is taken care of with a low-speed digitally-multiplexed channel which occupies a single bit of the basic PCM timeslot. As common channel interoffice signalling (CCIS) is deployed, the address signalling moves to dedicated channels. -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave