Anyone remember the OLD US dialtone? Sorta sounded like the signal now used as a busy signal. Same tone, but was continuous. When in high school, I got a garage full of old telephone step equipment, including dial tone and ring generators. We set up two digit dialing all over the neighborhood. Let's see... There were the 'A' relays that had two coils and were used to sense loop current. The A relay would drive the B relay, which had a copper slug on it making it slow to release. If the A released and the B did not, we interpreted it as a dial-pulse and advanced the stepper. A similar relay was used for digit separation... Long time ago! Harold On Fri, 5 Nov 1999 08:01:18 -0600 Jim Hartmann writes: > Speaking of pitch references, the dial tone on a (US) telephone is > 350hz + > 440hz, generally digitally synthesized and precise. > > A little web searching will turn up several references that say that > 440 is > indeed above middle C. > > > > > > > Keith Causey @MITVMA.MIT.EDU> on 11/05/1999 > 05:14:38 > AM > > Please respond to pic microcontroller discussion list > > > Sent by: pic microcontroller discussion list > > > > To: PICLIST@MITVMA.MIT.EDU > cc: > Subject: Re: tones on piano > > > Middle C's, (AKA C4) frequency is approximately 261.6255653Hz. > Guitar > tuning > forks are supposed to be exactly A 440.0. That places them at the A > "above" > middle C in contradistinction to some rumors on this list. As an > initial > proof: since 60cycle hum is only about 1 cycle per second lower than > a B 2 > octaves below middle C you can use your ears to determine the > relative > placement without too much extra gear outside of a piano, a > calculator, a > 440 tuning fork, and your ears. If anyone is interested in my > sources I > will > email them the scanned gif files of the profuse documentation on > this > subject. Thanks, and good luck - Keith Causey > > > Peter Tiang wrote: > > > > > > I think Jim was correct. > > > > > > According to standard, the note A below "middle C" is 220Hz. > > > Most tuning fork comes at this frequency. > > > > Nope. "A440" is definately the A *below* middle C. The 18th > century A > > below middle C was 415 (a semitone lower). Orchestras can and do > tune to > > other pitches than those. > > > > -karen > > > > > An octave up/down is doubling/halving of frequencies. > > > You have 12 semitones in an octave. > > > And the notes follows a logarithmic scale. > > > > > > So you have, > > > > > > ln k = (ln 2)/12 > > > > > > where k = multiplier for the next semitone > > > the constant 2 comes from the definition of what is an > octave, > > > constant 12 from the number of semitones in an octave. > > > > > > or k = 2^1/12 > > > > > > Regards, > > > > > > Peter Tiang > > > > > > ============================================================ > > > > > > ----- Original Message ----- > > > From: M. Adam Davis > > > To: > > > Sent: Thursday, November 04, 1999 2:42 AM > > > Subject: Re: tones on piano > > > > > > > I have heard, though may be incorrectly, that this is an > approximation > > > > (much like using 3.141592653), and that the actual formulae > used to > > > > develop the scale are somewhat more complex. > > > > > > > > -Adam > > > > > > > > Jim Hartmann wrote: > > > > > > > > > > Adjacent notes on the chromatic scale are at a ratio of > 2^1/12 > > > (1.059463). > > > > > Use A 440 (above middle C?) as your starting point. > > > > > > > > -- > > Regards, > > Karen McMurray > > ------------------------- BYTE CRAFT LIMITED > ------------------------ > > 421 King Street North, Waterloo, Ontario, Canada N2J 4E4 > > Tel. (519) 888-6911, Fax (519) 746-6751 > > info@bytecraft.com, support@bytecraft.com, > http://www.bytecraft.com ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.