wpmadden@ee.enet.dec.com (03/05/91)
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Is there anyone out there that has or knows where to find the
exact frequencies of the the touch-tone numbers.
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Wm P. Madden, Jr.
North Carolina State University - Raleigh, N.C.
INTERNET: wpmadden@eos.ncsu.edu Ma AT@T: (919) 781-6390
lewis@tramp.Colorado.EDU (LEWIS WILLIAM M JR) (03/05/91)
The Touch Tone (R) dial transmits two frequencies whenever a button is pushed. The low-band frequencies are selected by the row on the dial and the high-bands by the columns. Thus 697 Hz ----- 1 ----- 2 ----- 3 ----- Spare | | | | 770 Hz ----- 4 ----- 5 ----- 6 ----- Spare LOW | | | | 852 Hz ----- 7 ----- 8 ----- 9 ----- Spare | | | | 941 Hz ----- * ----- 5 ----- # ----- Spare | | | | 1209 1336 1477 1633 Hz HIGH The spares are used mainly on military sets for turning privacy/secrecy gadgets on and off and other, similar non-sense. The frequencies were selected after much, much work in the hope that strange noise hits, the customer whistling etc., etc. would not register as a valid digit. A full description can be found in the "Bell System Technical Journal" between 1960 and 1965.