Received: by bu-cs.BU.EDU (5.58/4.7) id AA14077; Wed, 11 Jan 89 01:15:03 EST Message-Id: <8901110615.AA14077@bu-cs.BU.EDU> Date: Wed, 11 Jan 89 0:59:57 EST From: The Moderator Reply-To: TELECOM@bu-cs.BU.EDU Subject: TELECOM Digest V9 #10 To: TELECOM@bu-cs.bu.edu TELECOM Digest Wed, 11 Jan 89 0:59:57 EST Volume 9 : Issue 10 Today's Topics: CLASS(sm) Service Re: NJ Bell CLASS Services Race conditions in a PBX Re: finding ringback numbers Re: Video Phones Re: Another lesson on 700/800/900 service Re: Remote Call Forwarding Manipulation TouchTone in Hong Kong [Moderator's Note: We have an overflow of mail in the past two days. I have a dozen messages backlogged, so please be patient. Your submission will appear within a day or two. And thanks for all the mail! P Townson] ---------------------------------------------------------------------- To: telecom@bu-cs.bu.edu From: westmark!dave@rutgers.edu (Dave Levenson) Subject: CLASS(sm) Service Date: 7 Jan 89 22:26:24 GMT New Jersey Bell has begun offering ISDN-based custom-calling services, under the service mark CLASS. One of these is called Caller*ID service. It displays the calling number while your phone is ringing. To use it, you buy (from the telephone company, or from others) a device that is bridged on to your standard tip/ring line and has a display on it. Does anybody know the signalling method between the CO and the caller-id display box? I have determined that it is in-band analog, and sounds like a modem. After the first ring, there is a burst of carrier, then some modulation, then more carrier, and then the next ring. The data-burst occurs only once, after the first ring, for each incoming call. The modulation technique and data format are probably public information, as you can (theoretically) buy the display box from anybody. But where is the information available? Bellcore... are you listening? -- Dave Levenson Westmark, Inc. The Man in the Mooney Warren, NJ USA {rutgers | att}!westmark!dave ------------------------------ To: uunet!comp-dcom-telecom@uunet.UU.NET From: ccicpg!wsccs!wes@uunet.UU.NET (Barnacle Wes) Subject: Re: NJ Bell CLASS Services Date: 2 Jan 89 07:16:02 GMT In article , judice%kyoa.DEC@decwrl.dec.com (L Judice / 201-562-4103 / DTN 323-4103) writes: > This seems slow to me, since I was under the impression that CLASS > was implemented in software on existing ESS switches... Any NJ Bell > folks out there have a schedule, or currently operating exchanges? I thought the CLASS services were being implemented on newly installed GTD-5s! Can any AT&T employees confirm or deny this? Wes Peters GTE Electronic Systems & Services :-) :-) -- Signature? What Signature? Oops, I left my .signature on Obie! (e-mail to wes@obie.UUCP) ------------------------------ To: comp-dcom-telecom@uunet.UU.NET From: hiraki@ecf.toronto.edu (Lester Hiraki) Subject: Race conditions in a PBX Date: Mon, 9 Jan 89 14:16:47 EST Does anyone know how to solve the following problem? Consider a simple PBX which works as follows: All incoming calls from trunks are routed to the attendant console. Outgoing calls are processed as follows. From an internal extention, the user dials the trunk access code (usually 9) and then the some valid number according to the North American Numbering Plan. The PBX accumulates the valid digits first and after receiving the last digit, seizes the first free trunk and signals-out the dialing information in a burst to the local CO. Imagine now that an incoming call arrives at a trunk but the CO has not yet applied the ring voltage - ie connexion was made during the silent window (ringing is usually 2s on and 4s off, say). Just at this moment someone within the PBX is making an outside call & the PBX seizes this trunk before ringing starts, in effect answering the call. The incoming caller is connected to the person waiting for his outside call to be completed. Assuming loop-start lines, can this race condition be avoided? Note, not all business have ground-start lines. I understand ground-start lines eleminate this very problem? Can someone explain how ground- start lines work? ------------------------------ Date: Mon, 9 Jan 89 08:58:54 PST To: telecom@bu-cs.bu.edu From: dmr@csli.Stanford.EDU (Daniel M. Rosenberg) Subject: Re: finding ringback numbers In article johnl@ima.ISC.COM writes: >I also note that telcos often use a range of prefixes, e.g. in New Jersey >they use 550 to 559 excepting 555. If you look at the assigned prefixes >and see ten in a row that are unused, that's probably it. >John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 492 3869 At least as of a few days ago, 550-xxxx, where xxxx are the last four digits of your phone number, will do ringback in North Jersey (201). This does not work for (most, if not all) payphones (but when it did, it was a favorite trick for the kids to leave the phone ringing in the Foodtown). -- ## Daniel M. Rosenberg /////// CSLI/Stanford //////////////// +1 (415) 328-1373 ## INTERNET: dmr@csli.stanford.edu //////////// UUCP: {ucbvax, decvax}!csli!dmr ## I've my opinions, Stanford theirs. I don't speak for them, nor they for me.# ------------------------------ To: mit-eddie!comp-dcom-telecom From: mit-amt!geek@mit-amt.MEDIA.MIT.EDU (Chris Schmandt) Subject: Re: Video Phones Date: 9 Jan 89 03:40:37 GMT In article nigel@CC.IC.AC.UK (Mad Nige) writes: >In the December issue of Gentlemen's Quarterly, (the US edition) there >is and ad from Panasonic for a few of their pieces of gear. The one >that struck me as most interesting was the Video Phone, which according >to the blurb transmits a still picture every 6.5 seconds. They are pretty simple. You need to buy a unit for each end, of course. Each consists of monochrome camera and monitor, plus a moderately low resolution frame store. Press a button, your frame is grabbed, and sent by modem to the other end, relatively low speed. Of course, you lose audio while you're your doing it, as the data transfer is in band. If I recall, it's about 4 bits per pixel, so you can see how a bit of encoding can get the image to the other end in that time. I believe that the various similar products use the same protocol so that you can exchange pix between them. ------------------------------ To: comp-dcom-telecom@uunet.UU.NET From: Joel B Levin Subject: Re: Another lesson on 700/800/900 service Date: 9 Jan 89 20:23:08 GMT In article scotts@bu-it.BU.EDU writes: |AT&T 900 is a curious monster indeed. It was designed as a "mass |termination" service. When you dial a 900 # by AT&T (such as the |"hear space shuttle mission audio" number) you get routed to one of |twelve "nodes" strewn throughout the country. These nodes are each |capable of terminating 9,000 calls >PER SECOND<. . . . This is also the AT&T service which allows those obnoxious television "polls" ("dial this number to vote yes, this other number to vote no, and by the way this costs fifty cents"). |The one last dialing pattern that is worth mentioning is what's |called, "cut through dialing". Try dialing 10220#. If Western Union |comes to your town, you'll get a FG-A style dial tone. . . . I haven't tried for a long time, but in Nashua NH (603-880-) this did work for Sprint, i.e. 10777 + # would get you the same peculiar dial tone that their dial-in access number would, expecting you to reply with your access code and destination number. This was convenient because you could reach their customer service by dialling the above followed by the special 6-digit numbers (without access codes). /JBL == UUCP: {backbone}!bbn!levin POTS: (617) 873-3463 INTERNET: levin@bbn.com ------------------------------ To: comp-dcom-telecom@uunet.UU.NET From: flatline!phaedrus@uunet.UU.NET (james hartman) Subject: Re: Remote Call Forwarding Manipulation Date: 9 Jan 89 18:26:51 GMT In article , DMG4449%RITVAX.BITNET@CORNELLC.ccs.cornell.edu writes: > Is there a relatively inexpensive device I could buy to attach to a standard > RJ11 telephone line which has both 3-way, and telco call forwarding as well as > the fact that there is another line in the house which would allow me to > remotely control call forwarding. I would want to be able to activate, > deactivate, and change the number it forwards to, but of course security is > important. Does such an inexpensive beast exist??? Uh, what about your computer? Write/adapt a demon to wake up at certain times and change the number forwarded, or set up an option as part of a dial-in program. After all, what else does your computer have to do when you're not around to keep it busy? -- Zaphod: "It doesn't look like any kind of vortex to me." Gargravarr: "It isn't. It's just the lift." phaedrus@flatline.uucp / uunet!sugar!flatline!phaedrus (James E. Hartman) ------------------------------ To: comp-dcom-telecom@husc6.harvard.edu From: ho@buengc.BU.EDU (shun E. Ho) Subject: Touch Tone in Hong Kong Date: 10 Jan 89 20:13:46 GMT In article "hugh_davies.WGC1RX"@Xerox.COM writes: >I rang the local British Telecom telephone sales office to enquire if the >new exchange (a TXE4A, I believe - judging by its inability to provide >dialtone on offhook in about 50% of occasions) in the St.Albans (where I >live) supported TouchTone dialling. The person I spoke to said, and I >quote, "What's TouchTone dialling?". Sigh. As of last summer, the tiny British continent of Hong Kong has TouchTone service in at least one of the central business districts. Telephone services in HK are provided by Hong Kong Telephone, a subsidiary of the Cable and Wireless Group of Britain. - Yue-shun ------------------------------ End of TELECOM Digest *********************