Telecom-REQUEST@MIT-XX.ARPA (10/31/85)
From: Moderator <Telecom-REQUEST@MIT-XX.ARPA> TELECOM Digest Wednesday, October 30, 1985 8:04PM Volume 5, Issue 58 Today's Topics: Re: Why the Vadic 3400 protocol is still alive ! Tone burst Rochester telephone service Active line indicators (a summary) modems ---------------------------------------------------------------------- Date: Sun, 27 Oct 85 22:46:52 EST From: Ron Natalie <ron@BRL.ARPA> Subject: Re: Why the Vadic 3400 protocol is still alive ! Sorry, but VADIC did make 3400 model accoustic couplers and they do work at 1200. We've got a whole pile of them around here. The only problem is all the new fangled phones don't have round receivers that can fit into the little rubber holes on the coupler ------------------------------ Date: Mon, 28 Oct 85 09:35:12 PST From: Erik Mueller <erik@LOCUS.UCLA.EDU> Subject: Tone burst Newsgroups: mod.telecom Subject: Re: Daa daa daa - the number... Summary: Expires: References: <8510210346.AA26008@UCB-VAX> Sender: Reply-To: erik@ucla-cs.UUCP (Erik Mueller) Followup-To: Distribution: Organization: UCLA Computer Science Dept. Keywords: In article <8510210346.AA26008@UCB-VAX> jcp@BRL.ARPA (Joe Pistritto) writes: > > The three tone burst at the beginning of phone intercept >announcements appears to be international, by the way. I recently dialed >a wrong number in Basel Switzerland (from the US), and got the three tone >burst associated with 'the number you have dialed is not in service, please >check the number and dial again', except that the announcement was in >German (!). I recognized the tones however, and realized what had >happened. I have only heard one set of tones however, does anyone know >what the different sequences mean? > > -JCP- If those are the same tones that I have heard in France (an arpeggiated major seven chord: 1 5 7, as I recall), we now have those same tones in certain Los Angeles ESSs as the standard local incorrect-code recording (not intercept). Speaking of intercept, I noticed that in California, they don't bother with AIS, CIB, or ONI intercept; they just give you a wrong number recording that is the same no matter what number you dial. Does anyone know why that is the policy here? Too many numbers to bother with it? Too many transient college students? Or is it only GTE that does this? -Erik ------------------------------ Date: Sun, 27 Oct 1985 18:36 EST From: Jon Solomon <JSOL%BUCS20%bostonu.csnet@CSNET-RELAY.ARPA> Subject: Rochester telephone service Well, basically it is a 3-fold process: 1) your local exchange gobbles up as much of the number as can be processed locally: In Step exchanges this is usually a "1", Crossbar and Electronic exchanges usually gobble the whole number and do their own translation/verification of the prefix (at least for calls within the area code), then it is passed to (2). 2) The local exchange sends the call to a toll switch. Step in this case passes the call as soon as the "1" is dialed. An interface to the toll switch gobbles the rest of the number up and passes it to the toll center using MF tones. The toll center dials a call to the area code chosen, using both LOC and Common Carrier lines (i.e. AT&T, Sprint, MCI, etc), connecting it to (3). 3) The local switch in Rochester then finally gets the call and dials the local number. When the call is answered, supervision gets back to the originating CO to begin billing. "Route Planning" happens usually at the Common Carrier level. At this point, at least, there is no mechanism to do route-planning at the local switch (plans were made at one point to implement that on a local switch, but I think divestiture put a monkeywrench in the plans). Therefore using this model, it is safe to say that your tones don't do much in the process of completing the call. Special tones (not dialable from a touch tone phone -- security in obscurity!) are used to complete calls (except for step by step which dial pulses into the exchange). Hope that helps. --JSol ------------------------------ Date: Tue 29 Oct 85 21:00:01-PST From: Ole Jorgen Jacobsen <OLE@SRI-NIC.ARPA> Subject: Active line indicators (a summary) Thanks to all who responded to my query, most of the designs I received would work, but careful evaluation and lenghty discussions with several electronics wizards led me to the following conclusion: What is needed is a self-powered line monitoring device which plugs in like any phone and does not steal power from the telco line, such devices can apparently be purchased (from DAK and others) for about $10. Some observations: Putting things in series with the telco line is not very nice because you need to get in at the house entry point which could be out of the way and the increased resistance in the line would cause some audio attenuation. None of the circuits described do a very good job of protecting the LED from ringing voltage (which is about 90V). The current during ringing can be large enough to zap an LED since it has low internal resistance and even clever zener diode designs may not provide adequate protection. Finally, I should say that no circuit was actually built, the analysis was done mostly on paper. The self powered "line monitor" just seems a much more elegant design, even if no telco power is stolen, oh well.... <OLE> <370> ------------------------------ Date: Wed, 30 Oct 85 13:23:18 EST From: "Marvin A. Sirbu, Jr." <SIRBU@MIT-MC.ARPA> Subject: modems The CCITT has adopted a standard for 9600 baud full duplex modems running over dial-up lines (V.32) which uses Trellis encoding (send redundant bids and do forward error correction). The design is based on research done by AT&T. Virtually all the modem vndors are working on V.32 compatible products. The only one I know to have hit the market already is from British Telecom. I would think it highly unlikely that any modem not compatilbe with V.32 will become a de facto standard. Marvin Sirbu ------------------------------ End of TELECOM Digest *********************