Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!casbah.acns.nwu.edu!accuvax.nwu.edu!nucsrl!telecom-request From: seanwilliams@attmail.com Newsgroups: comp.dcom.telecom Subject: Re: Pulse-Mode Frequencies? Message-ID: <15910@accuvax.nwu.edu> Date: 8 Jan 91 23:46:15 GMT Sender: news@accuvax.nwu.edu Organization: TELECOM Digest Lines: 42 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 19, Message 6 of 9 Eric Tholome writes: >> ...I am looking for the frequencies used in tone mode phones. I know each >> key generates two frequencies more or less based on C D and E music notes, >> but I would like something a little bit more precise. 1209 1336 1477 1633 <- Hertz ___ ___ ___ ___ | | | | | | | | | 1 | | 2 | | 3 | | A | 0697 When a key is pressed |___| |___| |___| |___| a single frequency ___ ___ ___ ___ from the low group | | | | | | | | and a single frequency | 4 | | 5 | | 6 | | B | 0770 from the high group |___| |___| |___| |___| are generated simul- ___ ___ ___ ___ taneously. Both | | | | | | | | frequencies must exist | 7 | | 8 | | 9 | | C | 0852 for the carrier equip- |___| |___| |___| |___| ment to recognize the ___ ___ ___ ___ signal. | | | | | | | | | * | | 0 | | # | | D | 0941 |___| |___| |___| |___| The frequency pairs shown above are used throughout the world where tone signalling is utilized. The tones have been carefully selected so that the processing circuits in the central office will not confuse them with other tones which may occur on the line. The time required for the central office to recognize any digit tone is 50 milliseconds with an interdigit interval of another 50 milliseconds. The term "Touch-Tone(tm)" is a trademark of AT&T. Sources: "Understanding Telephone Electronics" Texas Instruments Inc., 1983. "Data Communications: A User's Guide" Ken Sherman, Simon & Schuster, 1990. Sean E. Williams seanwilliams@attmail.com