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From: "M.Marking" <drivax!marking@uunet.uu.net>
Newsgroups: comp.dcom.telecom
Subject: Re: Touchtone History
Message-ID: <9706@accuvax.nwu.edu>
Date: 13 Jul 90 03:41:03 GMT
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X-Telecom-Digest: Volume 10, Issue 482, Message 4 of 11


jimb@silvlis.com (Jim Budler) writes:

) In article <9533@accuvax.nwu.edu> John Slater <johns@scroff.uk.
) sun.com> writes:

) >In article <9482@accuvax.nwu.edu>, roy@alanine.phri.nyu.edu (Roy
) >Smith) writes:

  (don't you love this...?)

) >>Sitting on the table behind his chair were
) >>about 3 or 4 single line desk sets, one touch-tone, the rest rotary.

) It was probably a Department of Defense phone. These phones looked
) like touch-tone, made noises *similar* to touch-tone, but were on the
) private DOD Autovon network. They were not pulse dialers. To my
) uneducated ear they were DTMF, but they were definately tone dialers.
) They had four extra keys for setting call priority....

Each of the buttons makes two tones, one based on row and one based on
column, selected so as not to be harmonics of each other. (Hence
*Dual* Tone Multi Frequency.) The frequencies are:

			1209	1336	1477	1653 Hz
		697 Hz	 1	 2	 3	 A
		770 Hz	 4	 5	 6	 B
		852 Hz	 7	 8	 9	 C
		941 Hz	 *	 0	 #	 D

Most phones don't use the last column, but CCITT defines it.