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Message Digest
Volume 28 : Issue 207 : "text" Format
Messages in this Issue:
Re: Walter's Telephones
Walter's Telephones
Re: Walter's Telephones
Re: Walter's Telephones
Re: Walter's Telephones
Re: Walter's Telephones
Re: Walter's Telephones
Re: Walter's Telephones
Re: What is this device called
Re: Walter's Telephones
Re: Walter's Telephones
Re: Skype apparently threatens Russian national security
Re: Skype apparently threatens Russian national security
Re: Cellphone tower coverage Qs
Re: Cellphone tower coverage Qs
Re: Cellphones and driving
Pop song phone number goes up for auction
Re: Cellphones and driving
Re: Cellphones and driving
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Date: Tue, 28 Jul 2009 02:10:23 +0000 (UTC)
From: wollman@bimajority.org (Garrett Wollman)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4lmme$1s1i$1@grapevine.csail.mit.edu>
In article comments attached to my article
<h4l6hl$1mr9$2@grapevine.csail.mit.edu>, our moderator wrote:
>Please tell us about the various combinations of mode and signal
>available to digital stations. For example, if a station has two
>separate broadcasts going on, as does channel 7 in Boston, are they
>both being transmitted as part of the same digital stream, or are they
>only logically linked and transmitted on separate physical channels?
ATSC digital television is a single MPEG tranport stream. One of the
multiplexed data streams is a description of the other data streams,
indicating the video format, the particular multiplexed data stream
that the video is on, where all the audio and data streams are, and
how to combine them all together into a "virtual channel". There is
also supposed to be electronic program-guide data, but few stations
bother to transmit data for anything other than the program currently
airing. Closed captions, V-chip ratings, and all the other stuff that
analog television puts on line 21 are all transmitted as separate
tables or separate multiplexed data streams.
Unlike with "HD Radio", all of the program services transmitted in
ATSC are treated identically, although the licensee can of course
change the bit budget allocated to each service by adjusting the
compressor's controls.
>I ask because I regularly get dropouts and pixelation on 7-2 when 7-1
>is coming in OK, and likewise have trouble with 44-3 or 44-4 when
>44-1 is fine. If they're all part of the same bit stream, why does the
>problem affect only some of them and not all?
Just coincidence. The (limited) Forward Error Correction in ATSC
takes place before the MPEG demux, so it's entirely chance that the
QRM should affect the transmission of bits in one time slice and not
another. It's likely that they are assigning a higher bandwidth to
the "main" program, which means that it's more likely to be affected
by noise, but with higher bandwidth, the display will repair faster,
so you don't see it. I'd have to ask my acquaintances over at channel
7 how they're divvying up the bandwidth.
-GAWollman
--
Garrett A. Wollman | The real tragedy of human existence is not that we are
wollman@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
Opinions not those | grants to rare events of meanness such power to shape
of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness
------------------------------
Date: Mon, 27 Jul 2009 22:08:37 -0500
From: Neal McLain <nmclain@annsgarden.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Walter's Telephones
Message-ID: <4A6E6BB5.80309@annsgarden.com>
Our moderator wrote:
> Expecting FM broadcast quality audio from a TV audio signal is like
> trying to record a song by holding a cassette recorder up to a
> radio. Sooner or later, those who attempt it have to admit that it's
> not a productive approach.
Oh, come on Bill, it's not that bad!
Back when I was working in cable TV, we used to offer a cable FM
service. We transmitted standard BTSC (or monaural) RF carriers down
the FM band, and connected the cable directly to the customer's FM
radio. A bit noisy, but certainly not as bad as holding a cassette
recorder up to a radio!
We even carried TV aural as part of the cable FM service. The headend
gear included frequency-tripling circuitry to change the deviation from
+/-25 to +/-75. I posted a description of the process back in 2003 at
http://massis.lcs.mit.edu/archives/reports/cable-fm-wfmt-mcclain
Scroll down to "The Rise of Cable FM".
Neal McLain
------------------------------
Date: Tue, 28 Jul 2009 17:35:34 +1000
From: David Clayton <dcstar@myrealbox.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <pan.2009.07.28.07.35.32.755886@myrealbox.com>
On Mon, 27 Jul 2009 10:51:53 -0400, Wesrock wrote:
> In a message dated 7/27/2009 12:07:39 AM Central Daylight Time,
> harold@hallikainen.com writes:
>
>> None of the stations I worked with put their control on their program
>> line. The program lines were generally driven with a WE 111C
>> transformer to drop the 600 ohm source resistance (studio equipment)
>> down to 150 ohms to drive the line. Another 111C converted it back to
>> 600 ohms at the transmitter.
>
> Just a matter of curiosity--what was the advantage of 150 ohm lines? 600
> ohms was the standard for telco lines, including program grade lines.
>
> Wes Leatherock
> wesrock@aol.com
> wleathus@yahoo.com
>
> ***** Moderator's Note *****
>
> I'm always tempted to answer these sorts of questions myself - I worked on
> the "Radio" board, after all - but then I realize that a lot of the things
> I "know" about program audio lines are just memories of the way we did
> things, and I'm not sure of the technical basis.
>
> Let's see: impedance varies with frequency, so (I'm guessing) I think 150
> ohms is closer to the impedance at the upper frequencies, thus giving a
> boost to the "high end" tones, and making equalization easier. Come to
> think of it, that would be _part_ of the equalization, wouldn't it?
Lower impedance lines/equipment are less susceptible to picking up noise
(especially hum) than higher impedance stuff, in audio you would generally
go for the lowest impedance possible to reduce the line's noise.
As well various types of audio cabling is made with a specific impedance,
so 150 ohms may well match those cables along with the interfaces.
--
Regards, David.
David Clayton
Melbourne, Victoria, Australia.
Knowledge is a measure of how many answers you have, intelligence is a
measure of how many questions you have.
------------------------------
Date: Mon, 27 Jul 2009 19:37:44 -0700 (PDT)
From: Neal McLain <nmclain@annsgarden.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <361e509f-f4c1-40ba-9720-edfa2d62be4a@s15g2000yqs.googlegroups.com>
On Jul 27, 8:56 pm, woll...@bimajority.org (Garrett Wollman) wrote:
> In article
<98b8d488-3f82-41bd-bca2-43648ae26...@x25g2000prf.googlegroups.com>,
> Neal McLain <nmcl...@annsgarden.com> wrote:
>
> >I'm not sure I trust that chart. I can believe that 12 and 13 could
> >be adjacent in Providence, but I doubt that there are three digital
> >stations all operating on Channel 7 in Rapid City.
>
> Actually, that's entirely possible, assuming they are all the same
> station, because the FCC now allows something called a "distributed
> transmission system": instead of using one big facility to serve their
> allocated coverage area, stations may elect to use multiple smaller
> transmitters, possibly with directional antennas, to serve their
> markets. A number of stations made the transition using DTS to reduce
> the cost, particularly in rural areas where an omnidirectional antenna
> would waste a lot of energy over sparsely-populated parts of the
> market.
>
> -GAWollman
> --
> Garrett A. Wollman | The real tragedy of human existence is not that we are
> woll...@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
> Opinions not those | grants to rare events of meanness such power to shape
> of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness
>
> ***** Moderator's Note *****
>
> Please tell us about the various combinations of mode and signal
> available to digital stations. For example, if a station has two
> separate broadcasts going on, as does channel 7 in Boston, are they
> both being transmitted as part of the same digital stream, or are they
> only logically linked and transmitted on separate physical channels?
>
> What about channel 44 in Boston? It has four separate subchannels: are
> they all just slots in one large bit stream coming out of WGBX's
> transmitter?
>
> I ask because I regularly get dropouts and pixelation on 7-2 when 7-1
> is coming in OK, and likewise have trouble with 44-3 or 44-4 when
> 44-1 is fine. If they're all part of the same bit stream, why does the
> problem affect only some of them and not all?
====================================================
Garrett:
After further thought, I agree that it's entirely possible,
particularly in a huge DMA like Rapid City. That DMA covers counties
in four states, two of which are isolated islands inside other DMAs.
Those isolated counties may be served by translators of Rapid City
stations, or they may have separate stations.
However, your statement "assuming they are all the same station"
doesn't fit the situation I just described. The three Channel 7
stations in the Rapid City DMA 7 have separate call signs and they're
affiliated with different networks. One of them (KSWY) is in Sheridan
County, WY, one of those isolated counties (I should have recognized
the Wyoming area code!).
http://www.dtv.gov/stationlist.htm
Neal McLain
------------------------------
Date: Tue, 28 Jul 2009 16:02:15 +0100
From: Steve Hayes <steve@red.honeylink.blue.co.uk>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4n3to$2c28$1@energise.enta.net>
Wesrock@aol.com wrote:
> In a message dated 7/27/2009 12:07:39 AM Central Daylight Time,
> harold@hallikainen.com writes:
>
>> None of the stations I worked with put their control on their program
>> line. The program lines were generally driven with a WE 111C
>> transformer to drop the 600 ohm source resistance (studio equipment)
>> down to 150 ohms to drive the line. Another 111C converted it back to
>> 600 ohms at the transmitter.
>
> Just a matter of curiosity--what was the advantage of 150 ohm lines?
> 600 ohms was the standard for telco lines, including program grade
> lines.
>
> Wes Leatherock
> wesrock@aol.com
> wleathus@yahoo.com
>
> ***** Moderator's Note *****
>
> I'm always tempted to answer these sorts of questions myself - I
> worked on the "Radio" board, after all - but then I realize that a lot
> of the things I "know" about program audio lines are just memories of
> the way we did things, and I'm not sure of the technical basis.
>
> Let's see: impedance varies with frequency, so (I'm guessing) I think
> 150 ohms is closer to the impedance at the upper frequencies, thus
> giving a boost to the "high end" tones, and making equalization
> easier. Come to think of it, that would be _part_ of the equalization,
> wouldn't it?
My understanding is that the original open-wire telephone lines did have a
characteristic impedance of about 600 ohms but, from having worked on
analogue carrier systems many years ago, twisted pair lines are about 135
ohms. We designed our carrier equipment to match this impedance. This would
give a reasonably flat response up to several hundred kilohertz but losses
at all frequencies were very high. That didn't matter much to the carrier
system - it could tolerate up to 40 dB of loss. I'd assume the same approach
is used for T1/E1 and DSL systems.
That sort of loss would be intolerable for ordinary wireline phones (the
circuit is duplex and adding much gain makes it oscillate) so they are still
designed to match 600 to 900 ohms. The mismatch doesn't matter much at low
frequencies or on short lines and the loss is reduced but there is a lot of
high-frequency rolloff on longer lines. This can be mitigated by adding
loading coils. Along with the line capacitance, they make the circuit into a
low-pass LC filter with reasonably flat response to around 3 kHz but little
or no transmission above that.
I'd guess that it's easier to use 150 ohms for landline feeds to broadcast
facilities where perhaps a 15 kHz bandwidth is required and just crank up
the gain and tweak the high frequency response a bit than it would be to use
600 ohms with or without loading coils and have to equalise the resulting
horrible rolloff. Not that I've ever worked on them...
--
Steve Hayes, South Wales, UK
----Remove colours from reply address----
------------------------------
Date: Mon, 27 Jul 2009 19:53:38 -0700 (PDT)
From: "harold@hallikainen.com" <harold@hallikainen.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <a559530f-8533-42ba-9ee7-be9cb6c000d8@q40g2000prh.googlegroups.com>
> ***** Moderator's Note *****
>
> I'm always tempted to answer these sorts of questions myself - I
> worked on the "Radio" board, after all - but then I realize that a lot
> of the things I "know" about program audio lines are just memories of
> the way we did things, and I'm not sure of the technical basis.
>
> Let's see: impedance varies with frequency, so (I'm guessing) I think
> 150 ohms is closer to the impedance at the upper frequencies, thus
> giving a boost to the "high end" tones, and making equalization
> easier. Come to think of it, that would be _part_ of the equalization,
> wouldn't it?
You've got it! Driving and loading the line with a lower impedance
makes the capacity of the cable pair have less effect. In many case,
no equalization was required at all. Just a transformer at each end.
There's a paper on the frequency response of a cable pair (not a telco
pair) with various source and load impedances at
http://www.richardhess.com/be/aes-80.htm.
Harold
------------------------------
Date: Tue, 28 Jul 2009 03:58:58 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4lt21$1u2$1@reader1.panix.com>
>***** Moderator's Note *****
>Please tell us about the various combinations of mode and signal
>available to digital stations. For example, if a station has two
>separate broadcasts going on, as does channel 7 in Boston, are they
>both being transmitted as part of the same digital stream, or are they
>only logically linked and transmitted on separate physical channels?
I've not heard of the DTS scheme but it makes sense. Think of LBJ's
"It's better to have him inside the tent pissing out..."
>What about channel 44 in Boston? It has four separate subchannels: are
>they all just slots in one large bit stream coming out of WGBX's
>transmitter?
One could assume so [and Rabbitears agrees], but magic *is*
possible. Look up "Channel 30" in DC and you'll see it is 10 subchannels
from two separate transmitter sites; WNVC is 30-1>30-5; on RF 24. WNVT is
-6 through -10 on RF 30.
>I ask because I regularly get dropouts and pixelation on 7-2 when 7-1
>is coming in OK, and likewise have trouble with 44-3 or 44-4 when
>44-1 is fine. If they're all part of the same bit stream, why does the
>problem affect only some of them and not all?
That's especially interesting since 44-1>-4 are all 480i; so they should
be equal in my thinking. On 7-1; it's HD with a video bitrate of 6x 7-2.
I'd think that 7-2 should be easier to decode, so there's something else
that I don't grok going on.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
------------------------------
Date: Tue, 28 Jul 2009 03:43:47 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4ls5i$c5b$1@reader1.panix.com>
wollman@bimajority.org (Garrett Wollman) writes:
>WETA uses a Dielectric TUP-O4-12-2 antenna, a high-gain broadband UHF
>panel antenna, which was installed a few years ago for the
>transitional DTV facilities of WJLA and WUSA, at a different site from
>the old channel 26 analog. So, no "retuning" required, or indeed
>possible. (The old tower, if I remember correctly, was in Virginia;
>the new tower is in far Northwest DC at the Maryland line.)
The old tower is next to Arlington Hospital. I wasn't aware they'd
abandoned it, at least for TV. They rent out space to others inc. WAVY
who was kicked out of their site up at Lee Highway when the ATT building
was sold.
But it does appear they are now up on RF Hill. Rabbitears IS useful!
>The rules have changed over time, and the FCC's approach to the rules
>has also changed. The FCC no longer models TV facilities using fuzzy
>photocopied charts derived from experiments done in the 1950s; now
>everything is done using the Longley-Rice propagation model.
...
>>No one has yet to offer a lucid explanation as to why their DTV coverage
>>was so much poorer than predicted.
>It seems widely agreed that the FCC's modeling did not accurately
>reflect real-world coverage of VHF DTV operations.
Indeed. Considering the complaining folks all had had viable NTSC
reception... Or did they move as well?
>It's the Media Bureau these days.
And, more importantly, Martin is gone as chair. Insiders tell me that
morale was so bad under him that when Copps took over as interum chair;
he got a overwheming standing ovation in the packed auditorum, BEFORE he
could say word one.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
------------------------------
Date: Tue, 28 Jul 2009 02:38:34 GMT
From: Tom Horne <hornetd@verizon.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: What is this device called
Message-ID: <Kwtbm.1314$646.872@nwrddc01.gnilink.net>
Robert Bonomi wrote:
> In article <QUnam.1071$MA3.310@nwrddc02.gnilink.net>,
> Tom Horne <hornetd@verizon.net> wrote:
>>> ***** Moderator's Note *****
>>>
>>> There were a variety of interface devices that were made available
>>> after the FCC mandated interconnection. I'm most familiar with the
>>> CDH, which was intended to connect POTS lines to customer provided
>>> equipment. It did the job, but it was too complicated: not only did it
>>> have separate supervision leads that were isolated from the talk path,
>>> but it had separate ringing leads as well. There might have been PBX's
>>> or other CPE which could access the CDH directly, but ordinary key
>>> equipment could not: to use it for CPE key equipment, you needed
>>> _another_ interface to match the CDH interface.
>>>
>>> Ma Bell had too many interfaces and they cost too much to install and
>>> rent: it was inevitable that the FCC would dictate type-acceptance and
>>> allow direct connections. I don't remember when that happended, but it's
>>> been the norm ever since.
>>
>> Yes Bill, but that doesn't help with stuff that is not type accepted.
>> Isn't the new term of art certified? I'm trying to devise a way to
>> patch the PSTN incoming calls to manual switchboards that predate
>> customer dialing. If you connect the interconnect terminals of some
>> of those boards it will look like an off hook condition to the PSTN.
>
>
> If you'd said -that- in the first place, you'd have gotten better first-round
> answers. <grin>
>
> Anything 'off the shelf' in the (even semi-) modern world is going to require
> quite a it of custom 'glue' logic to adapt that cordboard to the weirdness of
> the CPE side of the adapter box. You may as well just get one of the (many)
> registered, type-accepted, 'FCC part 68' qualified, 'phone line interface
> integrated circuits (whew!!), and roll your required custom interfacing logic
> around -that-. Such chips are only a few dollars (at most), quantity one.
>
I'm afraid that customizing chip logic is beyond my skill set. I was
hoping, vainly it seems, that there existed some box that took in a loop
supervised phone line and a supply of some form of power and put out a
voice pair, dry closure on ring, and some means to signal the outside
lines supervision state.
--
Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous
for general use." Thomas Alva Edison
------------------------------
Date: Tue, 28 Jul 2009 03:14:51 +0000 (UTC)
From: David Lesher <wb8foz@panix.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4lqfb$gsq$1@reader1.panix.com>
Richard <rng@richbonnie.com> writes:
>A sampling of channels on low VHF:
>Chan City
>5 Anchorage, AK
>3 Bethel, AK
>6 New Haven, CT
>3 Key West, FL
>6 Pelham, GA
>6 Wrens, GA
>2 Las Vegas, NV
And two DC ones the FCC staff will know well; if they can still
receive them at home....
7 WJLA
9 WUSA
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
------------------------------
Date: Tue, 28 Jul 2009 17:04:22 +0000 (UTC)
From: wollman@bimajority.org (Garrett Wollman)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Walter's Telephones
Message-ID: <h4nb2m$2cjs$1@grapevine.csail.mit.edu>
In article <h4lqfb$gsq$1@reader1.panix.com>,
David Lesher <wb8foz@panix.com> wrote:
>Richard <rng@richbonnie.com> writes:
>>A sampling of channels on low VHF:
[...]
>And two DC ones the FCC staff will know well; if they can still
>receive them at home....
>
>7 WJLA
>9 WUSA
No, those are on VHF-high, not VHF-low. (Our European Friends would
say "Band III, not Band I".)
-GAWollman
--
Garrett A. Wollman | The real tragedy of human existence is not that we are
wollman@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry
Opinions not those | grants to rare events of meanness such power to shape
of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness
------------------------------
Date: Tue, 28 Jul 2009 03:53:12 GMT
From: "Tony Toews \[MVP\]" <ttoews@telusplanet.net>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Skype apparently threatens Russian national security
Message-ID: <l1ss655nopkp660dcq7v205gqgsuc3muv6@4ax.com>
Thad Floryan <thad@thadlabs.com> wrote:
>Some background for Echelon, SORM, Carnivore, etc. can be read here:
A number of years back a client of mine was taken over by another company. As I
didn't trust the new IT department I installed OpenVPN on my laptop and my email
server so they couldn't snoop on any emails. This has worked quite well for me.
However this only ensures no one can snoop on emails between my email server and my
laptop. And very few people run their own web and mail servers.
We should really be using S/MIME encryption to encrypt the emails for the entire
connection from your computer to my computer so the NSA, CSIS (Canada's version of
the NSA and CIA), etc, can't snoop.. (Hows that for few acronyms guaranteed to
set off a few low level flags.) http://en.wikipedia.org/wiki/S/MIME You can use the
Thawte Web of Trust http://www.thawte.com/secure-email/web-of-trust-wot/ to get
yourself a free email certificate.
Programs such as Outlook Express/Windows Mail and Outlook do support S/MIME quite
nicely.
(Regretfully the email software I've been using since 1995, Eudora, has *lousy*
support for S/MIME. Apparently this is a fundamental architecture problem and
Eudora is no longer being upgraded. If I do need/want to start using S/MIME I'll
likely be using a dedicated email address just for those emails and use Outlook.
.Apparently Thunderbird is somehow being "upgraded"/"sideways changed" to beocme more
like Eudora but I haven't checked on that lately.)
I'd also like to see a lot more corporations using S/MIME encryption on their emails
as it's possible, for example, folks at your upstream provider could be snooping on
emails.
Now as to how S/MIME would work in a web browser for those who use Hotmail and Gmail?
I think Gmail now allows you to choose to always use a https or secured connection if
desired. That won't help if you're feeling particularly paranoid about the NSA and
the like but will help ensure that the folks at the coffee shop aren't snooping.
Tony (one of my job titles is paranoid pessimist)
--
Tony Toews, Microsoft Access MVP
Tony's Main MS Access pages - http://www.granite.ab.ca/accsmstr.htm
Tony's Microsoft Access Blog - http://msmvps.com/blogs/access/
Granite Fleet Manager http://www.granitefleet.com/
------------------------------
Date: Tue, 28 Jul 2009 19:38:16 -0700
From: Thad Floryan <thad@thadlabs.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Skype apparently threatens Russian national security
Message-ID: <4A6FB618.30808@thadlabs.com>
On 7/28/2009 9:22 AM, Tony Toews [MVP] wrote:
> Thad Floryan <thad@thadlabs.com> wrote:
>> [...]
>> Some background for Echelon, SORM, Carnivore, etc. can be read here:
> [...]
> We should really be using S/MIME encryption to encrypt the emails for the entire
> connection from your computer to my computer so the NSA, CSIS (Canada's version of
> the NSA and CIA), etc, can't snoop.. (Hows that for few acronyms guaranteed to
> set off a few low level flags.) http://en.wikipedia.org/wiki/S/MIME You can use the
> Thawte Web of Trust http://www.thawte.com/secure-email/web-of-trust-wot/ to get
> yourself a free email certificate.
> [...]
The solution I use is GPG (GNU Privacy Guard), somewhat akin to PGP as
was mentioned at several of the URLs I cited in the earlier article. It
integrates well with many common email clients (e.g., Thunderbird, et al)
and is what I insist people use if they need to send me passwords, and it
provides choices as to the depth/style of encryption.
>From 1983 to 1995 I designed/manufactured/sold a telephony device for
secure data connections over the phone line, with later models incorporating
Motorola's MC6859 DES chip. First/earlier models required using an external
modem, later/final models incorporated a builtin modem, initially modules
from Cermetek (IIRC) and later the Telebit module for higher speeds.
There's a funny story about that MC6859 chip. Upon arriving (late) one
day at my office, I found a two foot high stack of documentation and several
tubes of sample chips, including the MC6859, left earlier by the Motorola rep.
Atop the pile of documentation was a black bordered, sternly worded "NOTICE"
stating (paraphrased) "Products incorporating this chip may not be exported
from the USA without prior approval from the Office of Munitions Control of
the US Department of State blah blah blah".
When examining the pretty purple-colored ceramic MC6859 chips with gold legs,
I turned one over and, WHOA!, emblazoned on its underside was "MALAYSIA".
So much for the technology never leaving the country. :-)
***** Moderator's Note *****
This thread reminds me of the debate about the "Clipper Chip", which
was a governemnt-backed program that would have mandated that any
encryption device include the capability for the government to decode
the data which was encrypted.
RSA Security and other commercial firms opposed the program, and it
was never implemented. However, any widespread use of encryption will
revive the debate: the methods aren't important, but the central
question is "Should Uncle Sam be entitled to listen in on my calls or
read my emails"?
------------------------------
Date: Tue, 28 Jul 2009 11:42:34 +0000 (UTC)
From: techie@tantivy.tantivy.net (Bob Vaughan)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Cellphone tower coverage Qs
Message-ID: <h4mo7a$s2d$1@news.stanford.edu>
In article <4A6DC5A3.9000104@thadlabs.com>,
Thad Floryan <thad@thadlabs.com> wrote:
>Today's SF Chronicle COMPUTING column has some Q&As about cellphones
>and this URL was mentioned: <http://cellreception.com/>
>
>Curious, I wanted to see where the local cell towers were located for
>my carrier (AT&T Mobility grandfathered all the way back to Cellular One).
>I seldom have fewer than 4 (out of 5) bars on my phone's display, so I
>figured there would be a hive of towers especially here, Silicon Valley.
>
>Visiting this URL:
>
><http://www.cellreception.com/towers/towers.php?city=los%20altos&state_abr=ca>
>
>and clicking "[*] AT&T", I wondered where the towers were and had to zoom
>out to see a few.
>
>There's a cluster of 3 flanking Moffett Federal Airfield about 3.5-4 miles
>north from my home, another grouping of 5 about 8-9 miles east between Santa
>Clara and San Jose, then two NW about 20-25 miles away in Burlingame. That's
>it for the places I normally would be concerned about coverage.
>
>This doesn't make any sense to me for two reasons:
>1. I have excellent signal strength at my home, and
>2. if I dial 911 (on the cellphone) from home I get the local city's 911
> center, and if I dial 911 while driving along I-280 all the way up to
> San Mateo (just south of Burlingame) I get the CHP 911 dispatch.
>
>My two questions:
>
>1. is that tower spacing "normal"? The "cellreception" site claims to have
> all registered towers in its database of 135,800 towers last updated in
> May 2009.
See the notes on the site. It mentions that it doesn't have listings for
towers that are not registered in the fcc database, nor for towers owned
by third parties. It also dosen't have listings for carriers co-located on
another carriers tower. I'm guessing that they are basing the database on
the FCC Antenna Structure Registration, and not a specific transmitter site
license. I'm not sure if individual cell sites are even listed in the FCC DB.
I suspect that Nextel sites are more likely to be listed, given that Nextel
is/was a SMR licensee with interconnect capabilities, and not a cellular
licensee. Different service, different rules.
I know of at least one tower (at Foothill College) that is not shown on
the map. I forget who is actually on that tower, but there were at least
3 carriers when I last looked. The site is owned/leased by one of the site
management companies (Spectrasite?), and not by a specific carrier.
It is likely that there are additional cell sites that are not located on
a tower at all, but are installed on the roof of a building (there is a
office building along El Camino, next next to WalMart and Trader Joe's
which I recall as having antennas on it.)
Other places where you may find antennas include flagpoles (there are
examples at Palo Alto fire stations 3 (Rinconada Park), and 4 (Mitchell
Park), lamp posts (the old Elks Lodge parking lot next to Dianah's),
and church steeples. There are also some micro sites mounted on utility
poles (Junipero Serra @ Stanford Ave).
>
>2. how/why would I get routed to CHP's 911 while on I-280 headed NW even
> just a mile or two from home while I get routed to the local city's 911
> if I call from home? [I'm not complaining because that's exactly what I
> want to happen]
>
>The reason I'm puzzled is that when the service was still Cellular One they
>claimed a tower within 1/2 mile of my home and even assisted getting service
>to function within the local food supermarket which had a metal roof and
>zero reception. Later, as Cingular, again I was informed new towers were
>being installed. To date since AT&T acquired the contract, I've received no
>indication of new towers, only claims of "service improvements" -- given I
>really have no quarrel with AT&T Mobility, I accept that claim.
>
>Perhaps I should be asking: is there a better resource showing cellphone
>coverage and/or tower locations by carrier?
I know Jeff Leiberman has/had a list of cell sites in the San Lorenzo
Valley area, but I haven't looked at it in quite a while. I don't know
if it lists anything down in the Santa Clara Valley.
>
>I'm still scratching my head wondering how cellphone service works here at
>all. :-)
>
--
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie @ tantivy.net |
| P.O. Box 19792, Stanford, Ca 94309 |
-- I am Me, I am only Me, And no one else is Me, What could be simpler? --
------------------------------
Date: Tue, 28 Jul 2009 20:03:12 -0700
From: Thad Floryan <thad@thadlabs.com>
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Cellphone tower coverage Qs
Message-ID: <4A6FBBF0.1050606@thadlabs.com>
On 7/28/2009 9:23 AM, Bob Vaughan wrote:
> In article <4A6DC5A3.9000104@thadlabs.com>,
> Thad Floryan <thad@thadlabs.com> wrote:
>> [...]
>> 1. is that tower spacing "normal"? The "cellreception" site claims to have
>> all registered towers in its database of 135,800 towers last updated in
>> May 2009.
>
> See the notes on the site. It mentions that it doesn't have listings for
> towers that are not registered in the fcc database, nor for towers owned
> by third parties. It also dosen't have listings for carriers co-located on
> another carriers tower.
Red-faced, thank you! I now see those notes. :-)
> [...]
> I know of at least one tower (at Foothill College) that is not shown on
> [...]
> It is likely that there are additional cell sites that are not located on
> a tower at all, but are installed on the roof of a building (there is a
> office building along El Camino, next next to WalMart and Trader Joe's
> which I recall as having antennas on it.)
>
> Other places where you may find antennas include flagpoles (there are
> examples at Palo Alto fire stations 3 (Rinconada Park), and 4 (Mitchell
> Park), lamp posts (the old Elks Lodge parking lot next to Dianah's),
> and church steeples. There are also some micro sites mounted on utility
> poles (Junipero Serra @ Stanford Ave).
>
>> 2. how/why would I get routed to CHP's 911 while on I-280 headed NW even
>> just a mile or two from home while I get routed to the local city's 911
>> if I call from home? [I'm not complaining because that's exactly what I
>> want to happen]
It's possible those "undocumented" towers at Foothill College and other
sites north-westwards is probably why I get the CHP's 911 dispatch while
along I-280 instead of the local municipalities' 911 centers.
The 20 mile "gap" between Los Altos/Mountain View and Burlingame as depicted
on cellreception's site was puzzling, especially so given all the hills and
other radio obstructions along I-280.
Again, thank you for the info!
I'm going to poke around and followup if/when I find sites with
better/more information. It's odd (to me) the FCC wouldn't have ALL
cellphone (tower) transceivers in their database given how tightly they
seem to regulate the spectrum.
------------------------------
Date: Tue, 28 Jul 2009 09:48:07 EDT
From: Wesrock@aol.com
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Cellphones and driving
Message-ID: <d5a.4c6ca40d.37a05b97@aol.com>
In a message dated 7/27/2009 9:07:14 PM Central Daylight Time,
Wesrock@aol.com writes:
> ***** Moderator's Note *****
>
> They could install high-speed readers for cars with transponders,
> and promote the service and the time saved in the 'Fly By'
> lane. That would cost very little in relative terms, especially
> compared to the value of the time wasted by all those motorists.
I had not really considered that they did not have transponders since
they have been used on all the toll roads I have driven on in Kansas,
Oklahoma or Texas. It would be nice if the three states could agree
on an interchange, especially since they all use the same system, from
a firm with headquarters in Houston, and at least for the Oklahoma
turnpikes the bill (statement of usage--you have to prepay in $40
increments) comes out of Houston.
There are some transponder lanes in Oklahoma which have "ramp speed
75" signs posted on the entrance to those lanes.
--
Wes Leatherock
wesrock@aol.com
wleathus@yahoo.com
------------------------------
Date: Tue, 28 Jul 2009 10:16:37 -0700 (PDT)
From: hancock4@bbs.cpcn.com
To: redacted@invalid.telecom.csail.mit.edu
Subject: Pop song phone number goes up for auction
Message-ID: <bea626a5-32a3-4708-b3dd-00e61567d0fa@g23g2000vbr.googlegroups.com>
A telephone number related to the Jenny song is up for auction. For
details see:
http://www.kyw1060.com/--Jenny-s---Phone-Number-Goes-Up-For-Auction/4888510
------------------------------
Date: Tue, 28 Jul 2009 13:15:09 -0500
From: bonomi@host122.r-bonomi.com (Robert Bonomi)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Cellphones and driving
Message-ID: <fL-dnQox-qWw3fLXnZ2dnUVZ_jmdnZ2d@posted.nuvoxcommunications>
In article <pan.2009.07.27.07.26.42.838735@myrealbox.com>,
David Clayton <dcstar@myrealbox.com> wrote:
>On Sun, 26 Jul 2009 16:02:26 -0400, John David Galt wrote:
>
>> David Clayton wrote:
>>> Too many people reject attempts to reduce any problem if the proposed
>>> solution isn't somehow "perfect" in obtaining a 100% solution to the
>>> issue.
>>>
>>> I rather have 70% (or whatever the compliance rate actually is) less
>>> people using phones while driving because that reduces that particular
>>> risk to everyone else by that amount, if 30% continue to indulge in that
>>> sort of risky behaviour then it is still far better than the original
>>> situation.
>>
>> The vast majority of drivers are still phoning while driving (not a
>> scientific survey, just my personal observation).
>>
>> If we want drivers to obey this law, then let's increase the penalty
>> and/or create more enforcement mechanisms (for instance, have the red
>> light camera operators look for people phoning). Otherwise, repeal it.
>
>Hey, I reckon that any driver caught illegally using a phone should have
>the phone immediately confiscated and smashed to bits before their eyes.
>
>Give that sort of enforcement a few months of use and then see the
>compliance rate soar...... :-)
>
>--
>Regards, David.
>
>David Clayton
>Melbourne, Victoria, Australia.
>Knowledge is a measure of how many answers you have, intelligence is a
>measure of how many questions you have.
>
>***** Moderator's Note *****
>
>My first reaction to David's idea was "Get Real!" ... but then I
>remembered seeing film of a Connecticut State Trooper confiscating a
>radar detector, so now I'm not sure if it's such a far-fetched
>idea. Any lawyers want to weigh in?
The U.S. Constitution forbids 'takings' without 'just compensation', in general.
Things that are present in a place where they are forbidden to be can be
confiscated -- *temporarily* -- to remove them from the forbidden locale. But
they must be returned to the 'lawful' owner thereof, later, when request/demand
is made, *OR* the owner must be reimbursed the fair value thereof.
This is precisely _why_ the TSA handles detected 'forbidden' objects the way
they do -- you can either _keep_ your object, and make other arrangements for
your (or -its-) travel, or you can 'donate' it to the government, and proceed
with your scheduled travel. They do _NOT_ "confiscate" anything. <rolls eyes>
------------------------------
Date: Tue, 28 Jul 2009 21:18:39 -0500
From: gordonb.zrsqu@burditt.org (Gordon Burditt)
To: redacted@invalid.telecom.csail.mit.edu
Subject: Re: Cellphones and driving
Message-ID: <fNudnf98kMziLPLXnZ2dnUVZ_ridnZ2d@posted.internetamerica>
> The U.S. Constitution forbids 'takings' without 'just compensation',
> in general. Things that are present in a place where they are
> forbidden to be can be confiscated -- *temporarily* -- to remove
> them from the forbidden locale. But they must be returned to the
> 'lawful' owner thereof, later, when request/demand is made, *OR*
> the owner must be reimbursed the fair value thereof.
If that's true, please explain "civil forfeiture" and how, for
example, some antique store owner at an airport carrying enough cash
to go on an antiques-buying trip to numerous auctions gets his cash
confiscated (and he can't get it back) because he can't prove it
wasn't drug money. Or, for that matter, explain how a homeowner or
landlord can lose his home because his kid (or tenant's kid) has a pot
garden in the back yard. Or how some cities confiscate cars of the
wives and mothers of men/boys caught soliciting prostitutes.
> This is precisely _why_ the TSA handles detected 'forbidden' objects
> the way they do -- you can either _keep_ your object, and make other
> arrangements for your (or -its-) travel, or you can 'donate' it to
> the government, and proceed with your scheduled travel. They do
> _NOT_ "confiscate" anything. <rolls eyes>
My proposed solution to the penalties for driving under the influence of
(hands-free) cell phones:
1. You get a minimum of 24 hours in jail, with the phone. It will ring
often, all night. If you answer it, the 24 hours restarts and you
get a nasty electric shock. For the severely addicted, this may be
a life sentence.
2. You lose your phone number, and it will be forwarded to a recording
for the next year (and you have to pay for this) explaining that
you're not responsible enough to use a cell phone, with NO
forwarding number given.
3. You have to pay the early termination fee on your cell phone contract.
***** Moderator's Note *****
The Fifth Amendment states that
"... nor shall private property be taken for public use, without just
compensation."
I doubt that items confiscated because they were used in the
commission of a crime are considered to be "for public use", but I'll
defer to the constitutional scholars among us.
------------------------------
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