telecom@ucbvax.ARPA (08/14/85)
From: Moderator <Telecom-REQUEST@MIT-XX.ARPA>
TELECOM Digest Tuesday, August 13, 1985 5:25PM
Volume 5, Issue 17
Today's Topics:
900 (Dial-It) and equal access
Re: (700) 555-4141
Re: upper limit of bit rate over a voice grade line
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Date: Mon, 12-Aug-85 16:59:13 PDT
From: vortex!lauren@rand-unix.ARPA (Lauren Weinstein)
Subject: 900 (Dial-It) and equal access
Another case where the provider selects the carrier is with 900
area code (Dial-It) services, used for polling and information
services (Sports info, Dial-A-Space Shuttle, etc.) The Dial-It
network is exceptionally unique and I would expect it to be quite
a while before any similar services are offered by non-AT&T
entities. Also, pressure will be very high for local telcos to
automatically route 900 calls to AT&T (if they're not already,
anybody know for sure?) The reason for this is the mass publicity
that surrounds 900 numbers--they tend to be announced on national
television broadcasts (for example) and nobody is going to
try explain dialing access codes if you're not an AT&T default
subscriber on such programs. So, the alternate carriers and local
telcos will get swamped with irate calls from subscribers who
won't be able to get their 900 calls through during the programs
unless automatic routing is done. Given the number of people
who dial such calls, the pressure will be intense for such automatic
routing.
--Lauren--
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Date: Mon, 12 Aug 85 18:31:34 MDT
From: thomas%utah-gr@utah-cs (Spencer W. Thomas)
Subject: Re: (700) 555-4141
When I signed up for my (equal access) LD carrier, I got a note from
them that I should dial (700)555-4141 to verify that I was connected to
them (after a couple of weeks, to give the good old BOC time to process
the paperwork). I was supposed to get the "cannot complete call as
dialed" recording if I wasn't connected yet. Well, curious fellow that
I am, I called immediately, and got a recording "thank you for selecting
AT&T" (which was not the company I had selected). Anyway, at least some
of the carriers are publicizing this number to their customers.
=Spencer
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Date: Tue, 13 Aug 85 02:47 PDT
From: Gloger.es@Xerox.ARPA
Subject: Re: upper limit of bit rate over a voice grade line
The discussion I've seen here so far regarding the upper limit of
signaling rate over a voice grade phone line has all been restricted to
an analysis of analog phone channels. Actually, I think a large and
growing proportion of long-distance lines are themselves digital, at 56
kbps. (The actual, instantaneous rate is 64 kbps, but one bit in every
eight is lost to channel overhead.)
Not by coincidence, this 56 kbps is the same 56 kbps at which "the phone
company" has threatened us with digital phone lines. Technically all
that's missing is the local digital connections, from the long-distance
digital lines to the end user.
Obviously any channel which includes such a digital link has a very
hard, absolute upper limit of 56 kbps. Practically speaking, it's very
hard to even approach 56 kbps over such a channel, because any other
noise or distortion in the channel, such as in the analog links, just
subtracts away from the total available bandwidth. And that especially
includes the noise and distortion introduced by the "voice"-to-digital
demodulator and digital-to-"voice" modulator in the channel itself.
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End of TELECOM Digest
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