TELECOM Digest Sun, 16 Jan 94 23:04:00 CST Volume 14 : Issue 36 Inside This Issue: Editor: Patrick A. Townson Re: Unmetered Local Service (Danny Burstein) Re: Unmetered Local Service (Robert L. McMillin) Re: Shannon's Law (was Re: Hayes' New Modem) (Clarence Dold) Re: Shannon's Law (was Re: Hayes' New Modem) (Charles Randall Yates) Re: ISDN: Coming Soon to my House? (Al Varney) Re: SW-56 and ISDN Questions (Dave Cherkus) Re: Surcharge for Tone Dialing to be Dropped (A. Padgett Peterson) Re: Wanted: PC/Mac Voicemail Recommendations (Jonathan Reiser) Re: Announcing networkMCI (Atri Indiresan) Re: Cordless Headset Telephone (Mike D. Schomburg) Re: US Digital Cellular Standard (Stan Scalsky) Re: Hayes' New Modem (Stephen Satchell) Re: Network Outage in 205 NPA? (Paul Cook) TELECOM Digest is an electronic journal devoted mostly but not exclusively to telecommunications topics. It is circulated anywhere there is email, in addition to various telecom forums on a variety of public service systems and networks including Compuserve and GEnie. Subscriptions are available at no charge to qualified organizations and individual readers. Write and tell us how you qualify: * telecom-request@eecs.nwu.edu * The Digest is compilation-copyrighted by Patrick Townson Associates of Skokie, Illinois USA. We provide telecom consultation services and long distance resale services including calling cards and 800 numbers. To reach us: Post Office Box 1570, Chicago, IL 60690 or by phone at 708-329-0571 and fax at 708-329-0572. Email: ptownson@townson.com. ** Article submission address only: telecom@eecs.nwu.edu ** Our archives are located at lcs.mit.edu and are available by using anonymous ftp. The archives can also be accessed using our email information service. For a copy of a helpful file explaining how to use the information service, just ask. TELECOM Digest is gatewayed to Usenet where it appears as the moderated newsgroup comp.dcom.telecom. It has no connection with the unmoderated Usenet newsgroup comp.dcom.telecom.tech whose mailing list "Telecom-Tech Digest" shares archives resources at lcs.mit.edu for the convenience of users. Please *DO NOT* cross post articles between the groups. All opinions expressed herein are deemed to be those of the author. Any organizations listed are for identification purposes only and messages should not be considered any official expression by the organization. ---------------------------------------------------------------------- From: dannyb@panix.com (danny burstein) Subject: Re: Unmetered Local Service Date: 16 Jan 1994 13:54:29 -0500 (lots of arguments pro and against measured service vs. flat rate deleted) Umm, to all you folk out there, let me point out a reality of life. The telcos are in business to do one thing and one thing only. What's that? to provide phone service? BZZZT. wrong answer. They are in it ... TO MAKE.MONEY.FAST. (with apologies to David Rodes ...) They will configure the rates in such a way as to maximize their revenue. Pure and simple. Now in many cases this will also help people reduce their own costs. For example, The Telephone Company way-back-when realized that their 'long distance' equipment sat idle after business hours, and that it cost them a -LOT- to add capacity for that 2:15pm surge in calls, so they put in discount rates for after hours. This helped shift some usage away from peak daytime (which lowered their costs) AND brought in 'found' revenue by increasing the number of discretionary calls. If the 2:15 pm load was 10% higher, then they'd need more physical plant, and would (almost justifiably) have to raise rates as well. OTOH, most of the incomprehensable rate plans they've implemented have been designed solely to increase revenue, WITHOUT doing much good for the customers. For example: Here in NYC about 15 years ago NY Tel eliminated free directory assistance calls. Instead, tehy gave a ?50 cent? credit and offerred six free calls/month. Calls above the six would be $0.25 each (quantity and rates approximate from memory). The idea, they claimed, was that DA calls cost the company, and by extension the customers (never the shareholders, by the way) money. People who 'abused' DA would get charged and everyone else would benefit. Of course we've seen the credit disappear, and we've seen a complete elimination of any free DA calls ... I could go on and on, but the key point to keep in mind here is that the telcos are a business, not a service, and want to enhance their money streams. In -some- cases a general good comes of it (off peak pricing) but in most cases the only benefit is to the company. (or should that be The Company). dannyb@panix.com (or dburstein@mcimail.com) (10288) 0-700-864-3242 ------------------------------ Date: Sun, 16 Jan 94 16:14 PST From: rlm@helen.surfcty.com (Robert L. McMillin) Subject: Re: Unmetered Local Service On 14 Jan 1994 23:00:23 GMT, Pat wrote: > [TELECOM Digest Editor's Note: The thing Jack Decker and other pro- > ponents of flat rate billing seem to forget or ignore is that in most > instances of measured billing, the majority of telephone subscribers > actually pay LESS for service than with flat rate. [deletia declaring modem users a small minority who will get squeezed by per-minute rates] But the question in my mind is this: is it *really* the case that modem users are that small of a minority that they wouldn't be able to resist this sort of thing? It's happened slowly and quietly, but there are a *lot* of homes with personal computers in them. A goodly number, and I would bet a majority, have modems. In California, digital data service is coming in the guise of ISDN, or SDS as Pac*Bell insists on calling it. This digital service will not carry the 500 channels of one-way television that the cable companies and the telcos want to believe will drive their stillborn idea of the Data Superhighway; but rather, it, and its successors, will spark a far superior way of communication: e-mail, digital voice-mail, and tons of other digital services. In other words, the Data Superhighway will be a many-to-many network of peers, not a one-to-many broadcast network for The War Channel, Duck Hunting Network, and Macramevision (although this isn't entirely beyond the pale). By some estimates, as much as 50% of the existing traffic on the telco networks is data. If digital services are offered at reasonable prices and terms, there is absolutely no doubt that they can spur a *real* revolution in communications. Obviously, for Pac*Bell to offer ISDN now seems to me to say that they think there's enough people out there with modems who want this service that they'll succeed. I think they're right. ------------------------------ From: dold@rahul.net (Clarence Dold) Subject: Re: Shannon's Law (was Re: Hayes' New Modem) Organization: a2i network Date: Mon, 17 Jan 1994 01:34:56 GMT Of course, in the good old days, of printing _checks_ on a serial printer, hanging off a terminal, you would always overstrike the dollar amounts. That way, if there was a glitch, the number would appear bad. A good number would appear bolded. Clarence A Dold - dold@rahul.net - Milpitas (near San Jose) & Napa CA. ------------------------------ From: yatesc@eggo.usf.edu (Charles Randall Yates) Subject: Re: Shannon's Law (was Re: Hayes' New Modem) Date: 16 Jan 1994 05:57:08 GMT Organization: University of South Florida In article hummes@osf.org (Jakob Hummes) writes: > In article , goldstein@carafe.tay2. > dec.com (Fred R. Goldstein) writes: >> In article hummes@osf.org (Jakob >> Hummes) writes: >>> ...But there is an absolute limit (Shannon's Law). The >>> question was about the transmission over a *real* phone line. And that >>> means there exists *noise*. The limit of bps is proportional to the >>> logarithm of the signal to noise ratio. Unfortunately I don't remember >>> the constant factors. >> Shannon's law is, in plaintext, >> BPS(max) = Bw * log(2)((1+S)/N) >> That is, take the signal-to-noise ration (adding 1 to signal, so a >> negative SNR has some information present) and represent it as a power >> of 2. Multiply by bandwidth (in Hz) and you get BPS. > Of course, not! > But now I remember Shannon's Law (you have placed wrong the brackets): > BPS(max) = Bw * log(2)(1+(S/N)) > The addition of 1 is needed to unable a negative BPS-rate, which would > be nonsense. > [TELECOM Digest Editor's Note: And of course Murphy's Law says that > when you are attempting to copy something down in plain ASCII text > for transmission to a computer network you'll always get some one > or more parts of it bass-ackwards to confound the readers even more > than they are already. That error might have been Goldstein's or it > might have been mine. Regrets extended. Your editor, Murphy.] I'm the one who originally posted this question, for those who don't know. It's nice to know what Shannon's law says -- if you assume a 30 dB SNR and 3100 Hz bandwidth, the law above works out to about 31 kilobits per second. If you happened to get a quiet channel, say, 40 dB SNR, the equation returns about 41.2 kilobits per second. However, this is still quite a ways off from a full-duplex, 28.8 kbps link, or 57.6 kbps total transfer rate. So my question still stands: How do they do it? Are they assuming a particularly quiet channel? Are they assuming more than the standard 3100 Hz of bandwidth is available? Randy Yates ------------------------------ Date: Sun, 16 Jan 94 15:58:18 CST From: varney@ihlpe.att.com Subject: Re: ISDN: Coming Soon to my House? Organization: AT&T Network Systems In article knauer@ibeam.intel.com (Rob Knauerhase) writes: > After talking to five different people in the local GTE residential > and business sales offices (favorite quote: "What is ISDN?", from two > people in residential sales), I finally found someone willing to admit > that they could sell me ISDN service. Interestingly enough, their > price was $48/month for 2B+D, which would provide two voice lines and > two phone numbers. This is about the same price as two unmeasured > POTS lines -- what a deal. Actually not too bad -- but you have to get over the assumption that ISDN is ONLY for medium-speed digital data traffic. What's the price for just one phone number, able to complete to each B-channel? > Of course, this is GTE. There has to be a catch. For data, they > charge the same as measured-by-minute local calls. I asked if that > mightn't be perhaps the silliest way to bill it (data calls by the > minute), when a major benefit of digital telephony is that when I'm > not using it, I'm _not using it_! (mostly) Sorry, but when you use ISDN to place a B-channel data (non-packet) call, you have a data path reserved through the network for your call, just as in the case of a voice/modem/FAX call. At least as much equipment is needed for such a call as for a voice call. Sometimes supporting ISDN data requires equipment replacement or updates, adding to the costs of ISDN. > That of course didn't phase them. Even at pennies/minute, the > advantage of faster speed is removed by cost when I can do plain-ol' > 14.4K with compression for "free." Is _anyone_ bothering to campaign > phone companies and Public Utilities Commissions so that we can get > this tarriffed in a reasonable manner (at least in places other than > Oregon)? Some consumer groups will support the retention of flat-rate voice calls in various areas. I know of none that advocate the funding of ISDN deployment by placing those costs into the general rate base (forcing all telephone users to fund ISDN "free" data calls). And if cost recovery is only from ISDN fixed charges, very few customers will want ISDN. Who do you want to fund your "free" data calls. > [Side note for those keeping score: US West in Portland offers 2B+D > for $90/month, no limit on data. Of course, you can't make an ISDN > data call between GTE and US West just yet, but they're working on > it.] This is difficult to believe (but possible) that such data calls cannot be placed, since most US West and GTE areas support Switched 56 calls. ISDN B-channel data calls rate-adapted to 56Kbps are almost identical to and interwork well with Switched 56 calls. The Switched 56 dialing plan usually uses '#56' as prefix digits to let the CO know you aren't making a voice call -- with ISDN, this information in in the SETUP message from the customer's ISDN equipment. The interworking also allows 56K calls from ISDN customers to reach other countries that do not yet have ISDN in place. Al Varney ------------------------------ From: cherkus@fastball.unimaster.com (Dave Cherkus) Subject: Re: SW-56 and ISDN Questions Organization: UniMaster, Inc. Date: Sun, 16 Jan 1994 19:37:34 GMT Reply-To: cherkus@UniMaster.COM > 2. Here in the US what cities have been converted to ISDN, and who are > still operating at SW-56? You can get this info on-line from the Combinet BBS: By popular demand, the Combinet "BBS" providing information on ISDN availability in many areas of the US is now available via the Internet. The information is supplied by Bell Communications Research and various Operating Companies and is updated periodically as new information becomes available. To access the service, telnet to bbs.combinet.com and login as isdn (no password is required). After entering an area code and three-digit prefix, the service displays the availability of ISDN. Also displayed is information about carrier installation prices and monthly charges. For those without direct Internet access, the service continues to be available on a dialup basis using a 2400 bit/sec modem at (408) 733-4312. Dave Cherkus UniMaster, Inc. cherkus@unimaster.com ------------------------------ Date: Sun, 16 Jan 94 08:53:13 -0500 From: padgett@tccslr.dnet.mmc.com (A. Padgett Peterson) Subject: Re: Surcharge for Tone Dialing to be Dropped From: dave_oshea@wiltel.com (Dave O'Shea) I wrote: >> This is the scary part simce everywhere I go I see regional carriers >> attempting to eliminate "flat" and "unmetered" plans. As telecommuting >> and information hightway access begins to take hold, the elimination >> of unmetered local service is the biggest threat to individual >> connectivity that I can imagine. > Well, in a word, no. > If an employee is worth telecommuting, even a $4/hour connection > charge is fairly minor in the face of, say, a $65,000 salary/benefits > package. Even if you get charged that for eight hours a day, it's minor. Check the math -- a typical eight-hour-a-day work-year is 2000 hours. $4.00.hr would be U$8,000.00. Since the U$65k S+B package you mention really works out to about $35-$40k/year take home for a family, this would be 20-25% or about the same as a typical house payment. Besides, it is not the highest paid employees who would be the best candidates nor the largest group, it would be the lower level clerks, secretaries, accounts receivables, accounts payable, etc. employees who would make up the largest and best group. For example, it would not particularly benefit me (though I do a lot of things work-related from home) since it it usually the obscure things that require hands-on that I do. It would not be practical for me to have a full laboratory at home (though some say that I do already), however for someone who does all of their work with a terminal and a telephone already, it is very viable. > Most employees who would best benefit from telecommuting are the ones > who are well into long-distance calling areas. Disagree here also. Metro commuting is what takes the most time and LATAs are getting very big. I live 23 miles one way from my desk and it is a local phone call. Metro commuting is also what takes the most fuel and creates the most congestion. > And who knows -- I don't follow ISDN or related services too closely, > but it (and similar services) will become more widely available as the > cost of bandwidth falls. Don't hold your breath. Orlando is often touted as one of the cities with ISDN available, but the last I looked it was confined to a very small area that was not at either my workplace (10,000 employees) nor my home. Warmly, Padgett ------------------------------ From: guppy@panix.com (Jonathan Reiser) Subject: Re: Wanted: PC/Mac Voicemail Recommendations Date: 16 Jan 1994 09:31:40 -0500 Organization: PANIX Public Access Internet and Unix, NYC In AARNOLD@gsb-lira.stanford.edu writes: > We are building a low-cost PC or Mac-based voicemail announcement system > (1-4 line) from existing hardware and would like recommendations on > software and hardware. > Please advise directly by e-mail. Thank you! Prometheus' fax modem/voice mail software is pretty poor, and their technical support is even worse ... I had to jump thru hoops to get an answer to my question: "Why is it that I can't send faxes to my computer when my voice mail system is running?" The answer: Prometheus' software, when it is running the voice mail mode, cannot recognize the tones from certain fax machines ... if you're not going to be sending faxes to the computer, you might want to take a chance, but I just want you to be aware of that limitation. Note: I last tried this about eight months ago, maybe Prometheus has come up with something different or better. Regards and good luck, Guppy ------------------------------ Subject: Re: Announcing networkMCI Date: Sun, 16 Jan 1994 11:53:33 -0500 From: Atri Indiresan Paul R. Coen wrote: >> Is that what the MCI TV commercials with the little girl with >> the pseudo-[B]ritish accent standing in a puddle spouting >> existential gibberish are all about? > Is it a girl? I thought it was a boy. Then again, I didn't > look very closely. All I noticed was an overly-perfect child > dressed in weird black clothes and a really ghastly hat. And > the kid sounded like one of the brats from _Mary Poppins_. It was a girl -- the scene (and perhaps the actress?) were taken from the movie "The Piano". She is (or is suppposed to be) British. The scene is in New Zealand, around the turn of the century, and she just got off a boat from England, which would explain the clothes. While this says nothing about NetworkMCI, I do recommend the movie. Atri ------------------------------ Date: Sun, 16 Jan 94 09:43:54 CST From: mschomburg@ltec.com (Mike D. Schomburg) Subject: Re: Cordless Headset Telephone Concerning the recent request for information on cordless headset telephones, I have been searching for items like this ever since supervising a telco "trouble" bureau several years ago. The technicians would have to answer service calls at desks, and then usually walk to our nearby equipment room to perform tests. It seemed to me that a hands-free telephone would have a dramatic effect on productivity, but I never found the right phone for the job. A few months ago I saw an advertisement for a thing called the Ear Phone, made by Jabra Communications Corporation (I have no relationship with them) which is a small device that fits in your ear (like ear-bud headphones) and functions as both microphone AND headset. It can plug into a regular telephone headset jack, a personal computer (for voice control or annotation) or a CELLULAR PHONE. I haven't tried it out, but this sounds like a really cool application. The cellular phone has to have a special jack, but I am guessing this will become common (the jack). Once you've got a portable phone, who wants to use up one hand holding the dumb thing? Mike Schomburg mschomburg@ltec.com Lincoln Telephone ------------------------------ From: sscalsk@relay.nswc.navy.mil (Stan Scalsky) Subject: Re: US Digital Cellular Standard Organization: NSWC DL Date: Sun, 16 Jan 1994 17:21:51 GMT With all this talk about cellular standards is there anywhere to get copies of the standards? Does the cellular industry have a location for standards dissemination? Docs on N-AMPS/AMPS, TACS, or ETACS would be of interest. Thanks, stan sscalsk@relay.nswc.navy.mil ------------------------------ From: ssatchell@BIX.com Subject: Re: Hayes' New Modem Date: 16 Jan 94 17:11:28 GMT Organization: Delphi Internet Services Corporation goldstein@carafe.tay2.dec.com (Fred R. Goldstein) writes: > It was often said that a phone line couldn't go beyond 26000 bps or > so, based on the typical bandwidth and SNR. Today a good clean line > is more likely to be digitally switched at 64000 bps, which is well > above the Shannon limit (digitization is lossy), but you still get a > theoretical limit closer to 40 kbps. Thus V.34, at 28.8 kbps, is > pushing the envelope, but still possible. But it won't work on a line > that's transcoded down to 32 kbps, or just plain noisy. Note the 300 > to 3400 Hz nominal frequency range; the 3400 is a hard filter. The anti-aliasing filters used to be at 3400, particularly when they were implemented using passive-filter technology. Today, the modern line cards are using digital filtering or active filtering (using op-amps) and the anti-aliasing filters start having their effect at 3700 Hz. Draft Recommendation V.34 makes used of the extended bandwidth when available in selecting the symbol rate to use on a connection. The added benefit of shifting to a higher symbol rate ("baud" rate to you old-timers) is that the Draft-V.34 modems can try to avoid a low-frequency distortion problem caused by the transformers on certain line cards without having to shift down in speed. When looking at the Shannon limit, you have to look at more than just added noise in the channl. There is also noise caused by intermodulation distortion which seems to be nigh near impossible to remove from the network. The "rule of thumb" is that the quantization noise of a companded telephone channel is equivalent to 39 dB SNR for a single PCM channel, 36 dB SNR for two tandem (unsynchronized -- don't ask) PCM channels, and 34 dB SNR for three tandem PCM channels. Digital speech compression just adds to this, although I don't have number for it all. Stephen Satchell, Principal Satchell Evaluations, Incline Village, Nevada, USA Testing modems for magazines since 1984 ------------------------------ Date: Sun, 16 Jan 94 13:14 EST From: Proctor & Associates <0003991080@mcimail.com> Subject: Re: Network Outage in 205 NPA? I wrote: > Anyone know what happened with the telephone network in Alabama on > Monday? I got a call from a customer in Arab, and I get an > all-circuits-busy when trying to return his call on all AT&T, Sprint > and MCI. Did BellSouth lose a tandem switch? Oops. This turned out to be a local problem in GTE's switch here in Redmond. For some reason all of 205 was blocked from the local CO for at least two days. This is the same switch that serves the area that Microsoft's main campus is in, although I am sure they have some direct connection to their long distance carriers, so they probably weren't affected. Paul Cook 206-881-7000 Proctor & Associates MCI Mail 399-1080 15050 NE 36th St. fax: 206-885-3282 Redmond, WA 98052-5378 3991080@mcimail.com ------------------------------ End of TELECOM Digest V14 #36 *****************************