The Telecom Digest for November 03, 2010
Volume 29 : Issue 296 : "text" Format
Messages in this Issue:
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Date: Tue, 2 Nov 2010 12:02:26 -0400
From: Randall <rvh40.remove-this@and-this-too.insightbb.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Disconnected: Attention Passengers it's perfectly safe to use your cellphones
Message-ID: <01F61BD4-0A7A-48A9-87FB-B2D68C5A4E90@insightbb.com>
> From: David Clayton <dcstar@myrealbox.com>
> To: redacted@invalid.telecom-digest.org.
> Subject: Re: Disconnected: Attention Passengers it's perfectly safe
> to use your cellphones
> Message-ID: <pan.2010.11.01.23.28.12.978922@myrealbox.com>
>
> So the "bottom line" is that the current cellular mobile systems are
> designed on the assumption that the terminals can only connect to a
> limited number of geographically close base stations, and if this
> assumption is not me then the whole functionality is threatened.
>
> One more good reason to limit (or continue to ban) handset use on
> flights.
Isn't it the case that cell phone use in flight is not banned in
Europe? Planes aren't falling out of the sky at any appreciable rate
over there, are they?
Date: 2 Nov 2010 19:49:49 -0000
From: John Levine <johnl@iecc.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Disconnected: Attention Passengers it's perfectly safe to use your cellphones
Message-ID: <20101102194949.8297.qmail@joyce.lan>
>Isn't it the case that cell phone use in flight is not banned in
>Europe? Planes aren't falling out of the sky at any appreciable rate
>over there, are they?
You are mistaken (about the first point, not the second.) On
intra-European flights, I've gotten the usual announcement about
turning off mobile phones.
There are a few European airlines with in-flight microcells, but I've
never flown on one of them.
R's,
John
Date: Tue, 02 Nov 2010 16:10:46 -0700
From: Steven <diespammers@killspammers.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Disconnected: Attention Passengers it's perfectly safe to use your cellphones
Message-ID: <iaq5pl$47n$1@news.eternal-september.org>
On 11/2/10 12:49 PM, John Levine wrote:
>> Isn't it the case that cell phone use in flight is not banned in
>> Europe? Planes aren't falling out of the sky at any appreciable rate
>> over there, are they?
>
> You are mistaken (about the first point, not the second.) On
> intra-European flights, I've gotten the usual announcement about
> turning off mobile phones.
>
> There are a few European airlines with in-flight microcells, but I've
> never flown on one of them.
>
> R's,
> John
>
>
>
I for on am glad that they do not allow the use of Cell Phones on
planes, most people scream into the phone, and I have not figured out
why, I was on a Metro Link train the other day and the noise from cell
phone use was bad.
--
The only good spammer is a dead one!! Have you hunted one down today?
(c) 2010 I Kill Spammers, Inc. A Rot in Hell Co.
Date: Tue, 02 Nov 2010 13:37:27 -0700
From: Richard <rng@richbonnie.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Disconnected: Attention Passengers it's perfectly safe to use your cellphones
Message-ID: <j3t0d6l5nf9knqrhv99jj2qimeo659s3t3@4ax.com>
>***** Moderator's Note *****
>
>It's true that SSB transmitters can become garbled if they're off
>frequency by a large amount, but it's rare. Modern frequency-control
>circuits are more than adequate to keep an SSB transmitter within the
>"intelligible" range: the voice may sound a little "Donald Duck", but
>it will be intelligible in a properly maintained SSB receiver. In
>any case, SSB receivers usually have manual "clarifier" controls that
>may be used to improve the tone of a transmitter that's "on the
>edge".
>
>The problem arrises during a transition from AM to SSB: the carrier
>signals sent by AM transmitters will heterodyne with the
>Beat-Frequency-Oscillator (BFO) in the SSB receivers, causing
>unacceptable noise, increasing controller fatigue, and causing other
>traffic - yes, possibly emergency traffic - to be missed.
>
>It only takes a couple of hundred Hertz of frequency offset - which
>is, remember, the _combination_ of the BFO and carrier frequency
>errors - and the only thing a controller or other pilots will hear is
>a cat screech instead of a voice.
This is not a problem with modern crystal-controlled
frequency-synthesizing receivers. I use my ham HF transceiver to
listen to DBS-AM broadcasts on both the AM broadcast band and
short-wave. Sometimes reception is garbled due to multi-path
distortion in the channel upsetting the phase relationships of the
sidebands to each other and the carrier. Setting my receive center
frequency to that of the station and switching to SSB, I get clear
reception and no audible carrier beat. Any carrier beat is so close
to zero that it doesn't get through the audio stages.
Dick
***** Moderator's Note *****
With modern receivers and transmitters, probably not.
But ...
Air-to-ground communications have to work with ALL planes, even
those using out-of-date radios that can "drift" by several thousand
Hertz during warmup and prolonged use. Pilots, especially those in
remote areas, are a fiercely independent group, and they might not
agree that the cost of a new radio is justified when the old ones
still work.
Bill Horne
Moderator
Date: Tue, 2 Nov 2010 20:43:47 -0400
From: Telecom Digest Moderator <redacted@invalid.telecom.csail.mit.edu>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Happy anniversary cellphone!
Message-ID: <20101103004347.GA23819@telecom.csail.mit.edu>
On Sat, Oct 30, 2010 at 09:20:53PM +0000, Telecom Digest Moderator wrote:
> ***** Moderator's Note *****
>
> Between ASCII Teletype machines, the codes DC2 and DC4 were used to
> control the tape reader: they were labelled "TAPE ON" and "TAPE OFF"
> respectively, and a "local" machine could stop the tape reader on a
> "remote" machine by sending "TAPE OFF", and start it by sending "TAPE
> ON".
>
> Teletype machines had "answerback" capability: it was a hand-coded
> drum that sent a prerecorded id code, and it would respond whenever
> the machine received a "WRU" (Who Are You) code, which is an "ENQ"
> character in ASCII. I mention this because TWX machines were set up to
> send their answerback code automatically after they answered an
> incoming call. In Model 33 Teletype school, I was taught to code a
> "TAPE ON" (DC2) character as the last character sent during
> answerback, so as to start the tape reader on the calling machine: it
> was a courtesy that cut down on call durations.
>
> I don't know why 100-speed TWX machines used "hardware" flow control,
> i.e., why their Restrain signal was composed of simultaneous Mark and
> Space tones. It might have been a holdover from the 60-speed network,
> or possibly it was required by intermediate stations that couldn't add
> characters to the data stream, such as tape-relay points, TELEX <> TWX
> gateways, etc. I'm guessing, either way: I know that DC1 and DC3 are
> the workhorse characters for software flow control when a terminal is
> connected to a computer, but in the TWX world, it was "Restrain"
> instead of DC4/DC2 that was used to control tape transmission.
It seems that a lot of my readers are also TWX experts, and I have been
advised that I need to issue a correction to the above.
The ASCII DC2 and DC4 control characters were used to control the tape
punch of the remote machine in a TWX connection. The tape reader
responded, as the original poster suggested, to the DC1 (XON) and DC3
(XOFF) control codes.
Although I was correct in saying that the RESTRAIN signal would
temporarily stop a tape reader during a TWX call, the reader could
also be controlled by XON and XOFF, and it was the XON (DC1) control
code which was customarily set as the last character on an answerback
drum, so as to start the tape running on the originating machine as
soon as the answering TWX station had finished sending it's
(answerback) ID.
I guess they're right: the memory is the second thing to go. ;-)
--
Bill Horne
Moderator
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