TELECOM Digest V5 #58
Telecom...@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
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Date: Sun, 27 Oct 85 22:46:52 EST
From: Ron Natalie <r...@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
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Date: Mon, 28 Oct 85 09:35:12 PST
From: Erik Mueller <er...@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: er...@ucla-cs.UUCP (Erik Mueller)
Followup-To:
Distribution:
Organization: UCLA Computer Science Dept.
Keywords:
In article <8510210346.AA26008@UCB-VAX> j...@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
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Date: Sun, 27 Oct 1985 18:36 EST
From: Jon Solomon <JSOL%BUCS20%boston...@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
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Date: Tue 29 Oct 85 21:00:01-PST
From: Ole Jorgen Jacobsen <O...@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>
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Date: Wed, 30 Oct 85 13:23:18 EST
From: "Marvin A. Sirbu, Jr." <SI...@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
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End of TELECOM Digest
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