larry@uunet.uu.net (Larry Lippman) (09/24/89)
In article <telecom-v09i0395m09@vector.dallas.tx.us> gabe@sirius.ctr.columbia. edu (Gabe Wiener) writes: > Does anyone know when the common telephone dialtone (i.e. 350Hz and 440Hz > played together) was adopted? The standardization of dial tone to a dual frequency of 350 Hz and 440 Hz with a transmission level of -13 dbm was first proposed by AT&T and developed into CCITT Document AP III-84. I don't know the exact date of this CCITT standard, and don't have a copy handy, but I believe it was around 1963. This standard applies only to North America, however. Many European and other countries use a single frequency, most commonly 425 Hz. In is important to understand that this dial tone is produced by LINEAR mixing of two sinusoidal tone sources of 350 Hz and 440 Hz, and is NOT one frequency modulated by the other, which was the method employed with many previous dial tone supplies. The reason for the linear mixing is to reduce harmonics which may fall into the DTMF frequency domain and interfere with the interpretation of the first DTMF digit. The previous dial tone supplies were extremely rich in harmonics. The previous North American dial tone "standard" was 600 Hz modulated by 120 Hz; I use the word "standard" loosely here since in practice there was quite a variation because there was no technical _reason_ why the tone had to be precise. In older electromechanical CO's dial tone could be produced by a variety of apparatus, including motor-driven tone alternators, motor-driven pole-changing interrupters, electromagnet-driven pole-changing interrupters (i.e.,vibrators), ferroresonant AC-line powered devices, and in later years solid-state devices of varying stability. Interestingly enough, with one exception, I have never seen nor even heard of a call progress tone generator which used vacuum tubes. Technology in this area went directly from the electromechanical to the solid-state. The one exception was the "no-such-number" tone generator, which used vacuum tubes and made its debut around 1940; it has been affectionately called the "crybaby tone". This call progress tone (for lack of a better term) began rapidly disappearing in the later 1950's with the rapid implementation of intercept recorders which replaced it. The no-such-number tone had pretty much disappeared in the Bell System by 1965. The last "holdout" I am aware of which used this tone was Rochester Telephone, in Rochester, NY, and quite to my surprise I heard this tone when I misdialed a toll call to the Rochester area about four years ago. I was so taken aback - not having heard this tone for probably 20 years - that I was almost motivated to fetch a tape recorder and record it for posterity. :-) <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP {allegra|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> TEL 716/688-1231 | 716/773-1700 {hplabs|utzoo|uunet}!/ \uniquex!larry <> FAX 716/741-9635 | 716/773-2488 "Have you hugged your cat today?"
dtroup@uunet.uu.net (Dave Troup) (09/25/89)
Does anyone know what the recording alert tones are? You know-those
dee-doo-DOO, "The number you have reached..." What are the frequencies
to them. Ive NEVER been able to find out what those are.
thanks in advance!
"We got computers, we're tapping phone lines, knowin' that ain't allowed"__ _______ _______________ |David C. Troup / Surf Rat
_______)(______ | |dtroup@carroll1.cc.edu : mail
___________________________|414-524-6809______________________________john@zygot.ati.com (John Higdon) (09/26/89)
In article <telecom-v09i0405m01@vector.dallas.tx.us>, kitty!larry@uunet.uu. net (Larry Lippman) writes: > Interestingly enough, with one exception, I have never seen > nor even heard of a call progress tone generator which used vacuum > tubes. Technology in this area went directly from the > electromechanical to the solid-state. The one exception was the > "no-such-number" tone generator, which used vacuum tubes and made its > debut around 1940; it has been affectionately called the "crybaby > tone". The dial and busy/reorder tones in a stock Stromberg XY are generated by a device which uses a single vacuum tube. Ringback comes from a vibrating reed device (and sounds like a fart). The sound made by the dial tone generator is reminiscent of the old WE SXS "honker" tone but has a more mellow timbre. Although rapidly disappearing, the California desert is peppered with exchanges using the XY. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !
loren@amcom.UUCP (loren cahlander) (09/27/89)
In article <telecom-v09i0406m01@vector.dallas.tx.us> Dave Troup <carroll1! dtroup@uunet.uu.net> writes: >X-TELECOM-Digest: volume 9, issue 406, message 1 of 12 > Does anyone know what the recording alert tones are? You know-those > dee-doo-DOO, "The number you have reached..." What are the frequencies > to them. Ive NEVER been able to find out what those are. > thanks in advance! From the documentation that I have, there are four different sequences of tones: First Tone Second Tone Third Tone Tone Tone freq length freq length freq length Name Description (Hz) (10 ms) (Hz) (10 ms) (Hz) (10 ms) ====================================================================== NC No Circuit 985.2 38.0 1428.5 38.0 1776.7 38.0 Found IC Operator 913.8 27.4 1370.6 27.4 1776.7 38.0 Intercept VC Vacant Circuit 985.2 38.0 1370.6 27.4 1776.7 38.0 RO ReOrder 913.8 27.4 1428.5 38.0 1776.7 38.0 Loren D. Cahlander AMCOM Software, Inc. 5555 West 78th St Suite Q UUCP: uunet!rosevax!nis!amcom!loren Minneapolis, MN 55435 (612) 829-7445
tad@ssc.UUCP (Tad Cook) (09/30/89)
Regarding precise dialtone, it's true...the older dialtone was rich in harmonics, and interferes with a tone receiver trying to detect the first DTMF digit. I used to work for a company that made tone-to-pulse converters, and one of the requirements was that they be installed in offices with precise 350+440Hz dialtone, rather than the electromechanical motor driven monsters that were commong in offices without DTMF. Customers calling in with problems were usually asked about precise dialtone, and the wags around the office (Teltone) used to joke about the customers who said: "Hell yes it's precise dialtone! I checked it with a stobe light just last week!" Tad Cook tad@ssc.UUCP KT7H @ N7HFZ MCI Mail: 3288544
john@jetson.upma.md.us (John Owens) (10/03/89)
On Sep 24, 12:58pm, Larry Lippman wrote: > Technology in this area went directly from the electromechanical to > the solid-state. The one exception was the "no-such-number" tone > generator, which used vacuum tubes and made its debut around 1940; > it has been affectionately called the "crybaby tone". [....] > > The last "holdout" I am aware of which used this tone was Rochester > Telephone, in Rochester, NY, and quite to my surprise I heard this > tone when I misdialed a toll call to the Rochester area about four > years ago. [....] Actually, this tone (continuous rising for 1 second, continuous falling for 1 second, etc.) is still in use by C&P Telephone on the 301-867 exchange (West River, MD), for misdialed outgoing calls (e.g., dialing a 7-digit number for an exchange not in the local calling area). Calls to a non-working 867-xxxx, however, get routed to an AIC and get an intercept recording! I haven't tried dialing a 1+ call to a non-existent area code; I guess that would tell me if the local switch knows area codes or passes the 1+ call to a smarter tandem. This switch is being replaced by "the most modern electronic switching facility in Maryland" this Fall; can anyone tell from the use of the not-a-number tone what kind of switch I'm on? It's definitely not a stepper: touch-tone calls complete in milliseconds. No "custom calling features" are available; neither is Centrex, or Equal Access. Per-call and timed local billing is available. My guess is a #5 crossbar; reasonable? John Owens john@jetson.UPMA.MD.US uunet!jetson!john +1 301 249 6000 john%jetson.uucp@uunet.uu.net