The Slowest modem ever?
Thomas Munn
Am I right in assuming that 110 baud is the slowest they every made modems??
Thomas
David Ness
There may have been some earlier `experiments', but 110baud is
surely the first speed to gain any fairly wide distribution in the
computer context. I have a hunch that there were early teletypes
at even slower speeds, but to the best of my knowledge they were
never widely used with computers.
Ben Clifford
Thomas Munn (mu...@bigfoot.com) wrote:
: Am I right in assuming that 110 baud is the slowest they every made modems??
75 was used in viewdata modems (1200 from service provider to user, 75 from
user to service provider) - there wasn't much data to send up to the service,
just stuff that was typed in, and most people cannot type faster than 75 baud
anyway :-)
Ben
Tim Shoppa
In article <6ad4be$1...@nnrp4.farm.idt.net>,
Thomas Munn <mu...@bigfoot.com> wrote:
>Am I right in assuming that 110 baud is the slowest they every made modems??
As stated many times before, "the best way to get accurate information
on Usenet is to post inaccurate information".
Modems - and basic FSK (frequency shift keying) technology - dates back
at least to the 1920's. And I built a ELF receiver a couple of years
ago to listen to the encrypted ~0.1 baud FSK links used to communicate with
subs while they were submerged.
Tim. (sho...@triumf.ca)
Tom Van Vleck
CTSS supported TWX Teletypes in about 1963. I believe this was at 55 baud.
As I remember, these devices had mark and space inverted from the
Western Union network on purpose, to avoid tariff problems. On the MIT
Project MAC CTSS I think there was one phone line configured for this
speed. I should add something about this to
http://www.best.com/~thvv/terminals.html (as well as a description of
the IBM 7750 and the use of it by CTSS... weird computer, 48-bit word,
two instructions per word, memory divided into code memory and data
memory, specialzed for handling asynchronous telecommunications).
In article <34CA1D9D...@ibm.net>, dn...@ibm.net wrote:
> There may have been some earlier `experiments', but 110baud is
> surely the first speed to gain any fairly wide distribution in the
> computer context. I have a hunch that there were early teletypes
> at even slower speeds, but to the best of my knowledge they were
> never widely used with computers.
>
> Thomas Munn wrote:
> >
> > Am I right in assuming that 110 baud is the slowest they every made modems??
> >
> > Thomas
John A. Limpert
On Sat, 24 Jan 1998 16:20:28 GMT, mu...@bigfoot.com (Thomas Munn) wrote:
>Am I right in assuming that 110 baud is the slowest they every made modems??
I used to have a 45 baud modem that was used with a Model 19 Teletype
(60 WPM Baudot).
--
John A. Limpert
jo...@Radix.Net
Heinz W. Wiggeshoff
william m miller (w...@news.utk.edu) writes:
> I have a small 50 bps modem somewhere in my house.
I was going to chime in with smoke signals and jungle drums,
but my dim memories of Hollywood movies about these techniques
indicated a very high degree of information content for a few
smudges or booms in the air. Much greater than 50 baud.
George R. Gonzalez
Tim Shoppa wrote in message <6ad6pk$m4n$1...@nntp.ucs.ubc.ca>...
>In article <6ad4be$1...@nnrp4.farm.idt.net>,
>Thomas Munn <mu...@bigfoot.com> wrote:
>>Am I right in assuming that 110 baud is the slowest they every made
modems??
>
>As stated many times before, "the best way to get accurate information
>on Usenet is to post inaccurate information".
>
>Modems - and basic FSK (frequency shift keying) technology - dates back
>at least to the 1920's. And I built a ELF receiver a couple of years
>ago to listen to the encrypted ~0.1 baud FSK links used to communicate
with
>subs while they were submerged.
That's going back pretty far, but.. Good 'ol Alex Graham Bell
experimented with the "harmonic telegraph", which I think is basically
several telegraph signals onto one wire by frequency-division
multiplexing. This requires modems on both ends. About 1880? Baud
rate of maybe 1bps?
>
>Tim. (sho...@triumf.ca)
william m miller
I have a small 50 bps modem somewhere in my house.
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Chuck Maurer
On Sat, 24 Jan 1998 11:58:05 -0500, David Ness <dn...@ibm.net> wrote:
>There may have been some earlier `experiments', but 110baud is
>surely the first speed to gain any fairly wide distribution in the
>computer context. I have a hunch that there were early teletypes
>at even slower speeds, but to the best of my knowledge they were
>never widely used with computers.
>
>Thomas Munn wrote:
>>
>> Am I right in assuming that 110 baud is the slowest they every made modems??
>>
>> Thomas
Way back in the 70's I saw a machine that appeared to be going about half of 110
baud. It was printing futures market data.
MFree60760
This probably has no bearing on hardware, but....
A terminal program I found for CP/M-86 has settings all the way down to 50
baud.
That's a heck of a noisy line, 50 baud........
Mike
Mfree6
07...@aol.com
Kin Hoong CHUNG
Heinz W. Wiggeshoff (ab...@FreeNet.Carleton.CA) wrote:
: william m miller (w...@news.utk.edu) writes:
: > I have a small 50 bps modem somewhere in my house.
: I was going to chime in with smoke signals and jungle drums,
: but my dim memories of Hollywood movies about these techniques
: indicated a very high degree of information content for a few
: smudges or booms in the air. Much greater than 50 baud.
Probably not... all you need is a decent compression algorithm for
the kind of messages you are likely to transmit :-)
Cheers,
Kin Hoong
Robert Billing
In article <thvv-24019...@thvv.vip.best.com>
th...@best.com "Tom Van Vleck" writes:
> CTSS supported TWX Teletypes in about 1963. I believe this was at 55 baud.
"The usual speed for a teleprinter is 50 bauds, which makes the unit
equal to 20 milliseconds,"
From "an introduction to Creed teleprinters and punched tape equipment"
published by Creed & Co Ltd, Croydon in January 1958.
On P26 of the same publication is "A computer input output code". This
was I think the code used on the Mercury for Autocode, this idea is
supported by the fact that there is a manual correction in my late
father's handwriting, and he was certainly using the Mercury at that
time.
BTW I wonder what happened to Creed? In their day they were the
British equivalent of Teletype, but I haven't seen any signs of them
for years.
--
I am Robert Billing, Christian, inventor, traveller, cook and animal
lover, I live near 0:46W 51:22N. http://www.tnglwood.demon.co.uk/
"Bother," said Pooh, "Eeyore, ready two photon torpedoes and lock
phasers on the Heffalump, Piglet, meet me in transporter room three"
black
John A. Limpert wrote in message <34ca3706...@news1.Radix.Net>...
>On Sat, 24 Jan 1998 16:20:28 GMT, mu...@bigfoot.com (Thomas Munn) wrote:
>>Am I right in assuming that 110 baud is the slowest they every made
modems??
>(60 WPM Baudot).
Almost certainly 45.5, that being a standard rates.
We need to be careful about terms though, was it really a basebnad modem
or just a telegraph line adapter?
As it climbed further and further from the plane of the ecliptic, the
Voyager
spaceprobe sent (is still sending??) telemetry data a lot slower than 1
bit/second
but at much greater than one baud. Contrast with a modern modem that sends
data around 33,000 bits/second but only 2400 baud. Modulation rate is not
the
same as information rate.
Tony Duell
: BTW I wonder what happened to Creed? In their day they were the
: British equivalent of Teletype, but I haven't seen any signs of them
: for years.
I seem to remember reading somewhere (possibly in the RSGB Teleprinter
Handbook, probably not) that they were taken over by ITT, or at least
there were ITT-Creed machines about....
I don't suppose anyone knows where to get a toothed drive belt for the
reader in a Creed 444... I've got one that's in good condition apart from
that. It's the same pitch as a standard ASR33 belt (which I have piles
of) but shorter.
: I am Robert Billing, Christian, inventor, traveller, cook and animal
-tony (Got a 7E, 444 and 6S1...)
Steve Quest
Thomas Munn (mu...@bigfoot.com) wrote:
: Am I right in assuming that 110 baud is the slowest they every made modems??
My first acoustic modem was 300 baud, but I used it at 110, 75,
and 50 baud to connect to the local college's mainframe. Rural phone
connections were too crappy to get clean data at the zippy 300 baud so I'd
have to drop to 110 (typically) and sometimes slower. This was mid 1970's
sq
--
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============================> /_\ no law abridging the freedom
MicroPower FM Broadcasting-/ /\_/\ of speech, or of the press.
Douglas W. Jones,201H MLH,3193350740,3193382879
From article <6ad4be$1...@nnrp4.farm.idt.net>, by mu...@bigfoot.com (Thomas Munn):
> Am I right in assuming that 110 baud is the slowest they every made modems??
No. The old Baudot teletypes ran at 75 baud.
But the downlink datarate from some deep space probes is even lower, as is
the datarate used for ULF (ultra low frequency) radio signals to submarines.
The latter are mass produced (one per submarine in the US fleet), so they
almost certainly win for the lowest speed modems.
Doug Jones
jo...@cs.uiowa.edu
Joseph M. Newcomer
The slowest I ever heard of was the one that uploaded commands from
Earth to Voyager. 6 bits per second.
joe
On Sat, 24 Jan 1998 16:20:28 GMT, mu...@bigfoot.com (Thomas Munn)
wrote:
>Am I right in assuming that 110 baud is the slowest they every made modems??
>
>Thomas
Joseph M. Newcomer
newc...@flounder.com
http://www3.pgh.net/~newcomer
David Thompson
I worked for a news wire service and they still receive some 45 baud signals
(maybe 45.5). It was really a little faster (in characters per second)
since the word size was five or six bits (although you have shift in/out).
Watching this on a line monitor was pretty amazing. I would say the term
modem has to be applied pretty loosely to describe the equipment used for
transmission.
Thomas Munn wrote in message <6ad4be$1...@nnrp4.farm.idt.net>...
Carl R. Friend
Steve Quest, in article nr. <6ahd9k$8...@examiner.concentric.net>, wrote:
> My first acoustic modem was 300 baud, but I used it at 110, 75,
> and 50 baud to connect to the local college's mainframe.
That same FSK modem is good right on down to DC, so you can make
it as slow as you want. Those devices weren't tied to a set comms
bit-rate the way "new" ones are.
--
______________________________________________________________________
| | |
| Carl Richard Friend (UNIX Sysadmin) | West Boylston |
| Minicomputer Collector / Enthusiast | Massachusetts, USA |
| mailto:carl....@stoneweb.com | |
| http://www.ultranet.com/~engelbrt/carl/museum | ICBM: N42:22 W71:47 |
|________________________________________________|_____________________|
Tom Watson
In article <6ad4be$1...@nnrp4.farm.idt.net>, mu...@bigfoot.com (Thomas Munn)
wrote:
> Am I right in assuming that 110 baud is the slowest they every made modems??
>
Most (if not all) modems that were of the FSK variety will signal down to
DC (0 baud). For the Bell 103 type modems, the upper speed limit is
typically specified at 300 bps. Given "really good" line conditions, a
speed of 450 bps can be had.
These (bell 103 type) modems use frequency shift keying with a 200 Hz
shift, and with the higher data rates have problems with signal/noise
limits of discriminators. Two sets of frequencies are used for USA type
modems, 1070/1270 and 2025/2225 Hz. International standards use a
different (lower) set of frequencies.
The only problem with the lower data rates on the modem is that some
modems have a "space disconnect" "feature" that will terminate the call if
the modem is held at the space frequency for an extended period of time
(over 1 sec.).
Most currently available modems sold today have some sort of FSK
capability, usually conforming to the 103 standard. You can try your
modem to see if it has these standards, but it usually takes a few
commands to limit the speed to such a slow one.
As for other FSK transmission modes, there was a 1200/75 system used for a
while (before 1200 full duplex became popular). Given its improvement
over 300 bps, it was quite amazing. This standard (bell 202) continues to
this day in the form of caller ID messages on phone lines.
As for terminal equipment, the slowest 8 bit ascii stuff was 110 bps for
both directions (10 characters/sec). There were asymetrical ones 120
chars/sec outbound, 7.5 chars/sec inbound (1200/75), but they faded fast.
In the 5 bit "baudot" code, things were slower. Most of the early
teleprinters were 6 chars/sec (60 wpm), and used a 45.45 bits/sec rate.
These typically used current loops for transmission, and NOT modems.
Later on, Western Union DID use modems to transport data to its Telex
machines, but this was done only for simplicity reasons (an audio line was
easier to get than a current loop line).
Just some history.
--
t...@cagent.com (Home: t...@johana.com)
Please forward spam to: anna...@hr.house.gov (my Congressman), I do.
Charlie Gibbs
In article <34caa802...@news.dhc.net> cma...@dhc.net
(Chuck Maurer) writes:
>On Sat, 24 Jan 1998 11:58:05 -0500, David Ness <dn...@ibm.net> wrote:
>
>>Thomas Munn wrote:
>>
>>> Am I right in assuming that 110 baud is the slowest they every made
>>> modems??
>>
>Way back in the 70's I saw a machine that appeared to be going about
>half of 110 baud. It was printing futures market data.
It was probably some sort of Baudot machine (the most common example
might be a Teletype model 32) on the Telex network. These machines
sent the 5-bit Baudot code at 45.45 baud. Well, sort of... the start
bit and the 5 data bits took 22 milliseconds each, while the stop bit
was 31 ms long. This works out to 163 ms per character, or about 6
characters per second.
Then along came TWX with those speed-demon model 33s and 35s,
running at 10 characters per second (110 baud). Hot stuff.
--
cgi...@sky.bus.com (Charlie Gibbs)
Remove the first period after the "at" sign to reply.
danny burstein
Well, if you're really looking for slow digital signals, there's the 13
year sunspot cycle.
Or even better, the ?15 million year? warm-up/cool-down one
--
_____________________________________________________
Knowledge may be power, but communications is the key
dan...@panix.com
[to foil spammers, my address has been double rot-13 encoded]
Marco S Hyman
"Charlie Gibbs" <cgi...@sky.bus.com> writes:
> It was probably some sort of Baudot machine (the most common example
> might be a Teletype model 32) on the Telex network. These machines
> sent the 5-bit Baudot code at 45.45 baud. Well, sort of... the start
> bit and the 5 data bits took 22 milliseconds each, while the stop bit
> was 31 ms long. This works out to 163 ms per character, or about 6
> characters per second.
Yep. Called 60 WPM (words per minute). My first (and only :-) modem
was a ham radio terminal unit for a model 19 at 45.45 baud.
But what speed did the navy use on its vlf links used for
communications with submarines? For some reason I think it is
measured in seconds/bit, not bits/second. Anyone got a cite?
// marc
Lisa or Jeff
Per the last post, when did modems appear for teletypewriters instead
of 'current loop' devices?
I think the Bell System's TWX used current loop, somehow super imposed
on voice lines. They may have modulated the signal for carrier purposes
at the phone company, not customer location. (In 1939 they were getting
into carrier transmission and other techniques of multiplexing, which
included telegraph signals as well as voice.)
J. Chris Hausler
Thomas Munn <mu...@bigfoot.com> writes:
>Am I right in assuming that 110 baud is the slowest they every made modems??
>
This was the slowest speed used commonly for computers in the
1960's, however if you consider that a "modem" just translates
a baseband signal (like RS232) to a carrier signal and back
again, there were early digital telemetry systems for railroad
signalling which were only a few bps. There is currently a
group of Morse telegraph fans which use 103A type modems to simulate
a classic telegraph circuit. The early Radio Shack direct
connect modems are most popular with them. A 103A type modem will
work down to "DC" ;-)
Chris
Le Guerrier Louis-Luc
Steve Quest (Squ...@cris.com) wrote:
:
: Thomas Munn (mu...@bigfoot.com) wrote:
: : Am I right in assuming that 110 baud is the slowest they every made modems??
:
: My first acoustic modem was 300 baud, but I used it at 110, 75,
: and 50 baud to connect to the local college's mainframe. Rural phone
: connections were too crappy to get clean data at the zippy 300 baud so I'd
: have to drop to 110 (typically) and sometimes slower. This was mid 1970's
:
: sq
In the end 80s, I got a used Tandy 300 bps modem. I used it to connect to
my present network but that was quite slow. I got a 2400 in 1991 which I
still own and use from time to time. I've been heroically been able to sell
my 300 bps Tandy in 1993 for $10! And that thing couldn't even dial so you
need a phone to make the calls first.
Since then I've bought a 28800 bps modem from PPI and I like it very much. I
once tried to transfer at 300bps
with it just for fun. Is it possible to transfer
at a slower rate for such a modem? It would be quite oddball.
Louis-Luc
bma...@iglou.com
On 1998-01-24 sho...@alph02.triumf.ca(TimShoppa) said:
>Modems - and basic FSK (frequency shift keying) technology - dates
>back at least to the 1920's. And I built a ELF receiver a couple
>of years ago to listen to the encrypted ~0.1 baud FSK links used to
>communicate with subs while they were submerged.
>Tim. (sho...@triumf.ca)
Perhaps you might know something about why the FCC limits 56K modems to a
maximum speed of 53 Kbps. Is there something special about 56 KHz, or some
multiple of that frequency?
Net-Tamer V 1.08X - Test Drive
Robert Billing
> Perhaps you might know something about why the FCC limits 56K modems to a
> maximum speed of 53 Kbps. Is there something special about 56 KHz, or some
> multiple of that frequency?
Without doing the arithmetic I suspect that they are trying to avoid
the sort of problem that the EBU[1] have made for themselves.
The EBU has chosen a sampling frequency for digital television, which
is a direct submultiple of not only the civil and military aviation
distress channels, but the bottom ILS channel as well.
[1] European Broadcasting Union
--
I am Robert Billing, Christian, inventor, traveller, cook and animal
Charlie Gibbs
In article <tsw-260198...@cypher.cagent.com> t...@cagent.com
(Tom Watson) writes:
>Most (if not all) modems that were of the FSK variety will signal
>down to DC (0 baud). For the Bell 103 type modems, the upper speed
>limit is typically specified at 300 bps. Given "really good" line
>conditions, a speed of 450 bps can be had.
I managed to push mine to 600 bps. At this speed I got an error
every 50 or 100 bytes, but that was good enough to read messages
off a local BBS (Frog Hollow, which is still running, although
on MUCH newer hardware). And the difference in speed was quite
impressive at the time. Frog Hollow had an S-100 modem card that
could run as fast as 710 baud. Apparently 450 baud worked quite
well, but I didn't want to take the time to hack my serial port
to run at such an oddball speed.
BTW a friend and I hacked auto-dial into our manual modems by
installing a relay in series with the phone line and driving
it off the DTR line. A home-brewed driver for MEX gave us the
ability to pulse-dial as fast as 20 pulses per second if the
central office could handle it - it was almost as fast as tone
dialing. If we didn't see a carrier after a timeout interval,
we assumed the line was busy and dialed again. We had automatic
redial on busy, working through a list of phone numbers, and
the machine would beep loudly when it finally got a connection,
so I could be off doing something else while waiting to get
through to a busy BBS. All on an IMSAI running CP/M. Heaven.
Dr. Peter Kittel
In article <34fd181d....@206.210.64.12> newc...@flounder.com (Joseph M. Newcomer) writes:
>
>The slowest I ever heard of was the one that uploaded commands from
>Earth to Voyager. 6 bits per second.
I just read about the old Pioneer probe, now being outside our planetary
system. The article said it needs several seconds per bit.
--
Best Regards, Dr. Peter Kittel // http://www.pios.de of PIOS
Private Site in Frankfurt, Germany \X/ office: peterk @ pios.de
Ron Hunsinger
> Perhaps you might know something about why the FCC limits 56K modems to a
> maximum speed of 53 Kbps. Is there something special about 56 KHz, or some
> multiple of that frequency?
As I understand it, it's not so much a question of frequency as power. The
higher the frequency, the more power there is in a signal of a given
amplitude.
Reducing the amplitude is tantamount to reducing the number of bits per
sample, so they can't do that and still get 56K bits per second. (There's a
hard limit of 8K samples per second.)
So the problem is that at 56K bits per second, the signal can have more
power than is considered safe for any human ears that might happen to
listen in on the line. They're trying to get a waiver, or at least
relaxation, of the guideline, but until then 53K uses all the power that's
permitted.
To put the problem in sharp relief, consider the plight of someone like a
phone operator or repair person who is wearing a headset and must be able
to tap into lines more or less at random. Each time they touch a line
carrying a 56K connection, they get a loud blast through an earpiece that
they can't quickly remove. OHSA would like that person to be able to reach
retirement with their hearing still intact.
The safety issue seems a little more important than getting an extra 5%
speed through a line that is nominally an audio connection. Especially
since, if you really need the extra speed, you can go to ISDN. Presumably,
repair people know whether a line is digital (ISDN) or audio, and know
better than try to listen in on the former.
And ordinary phone customers might accidentally dial a number connected to
a 56K modem, and get their ears blasted by the modem's carrier signal.
Accidentally dialling an ISDN phone number doesn't have the same risk.
-Ron Hunsinger
Heinz W. Wiggeshoff
Ron Hunsinger (hns...@sirius.com) writes:
>
> As I understand it, it's not so much a question of frequency as power. The
> higher the frequency, the more power there is in a signal of a given
> amplitude.
> ... [Someone listening to a line] ...
> carrying a 56K connection, they get a loud blast through an earpiece that
> they can't quickly remove. OHSA would like that person to be able to reach
> retirement with their hearing still intact.
Bingo! The best way to discourage telemarketers, aside from the
answering machine. 'Pump up the volume.'
Seriously, I read somewhere that telco line and switching equipment was
the limiting factor. Of course, they MIGHT want you to pay for ISDN.
Ian Stirling
Ron Hunsinger <hns...@sirius.com> wrote:
:> Perhaps you might know something about why the FCC limits 56K modems to a
:> maximum speed of 53 Kbps. Is there something special about 56 KHz, or some
: As I understand it, it's not so much a question of frequency as power. The
: To put the problem in sharp relief, consider the plight of someone like a
: phone operator or repair person who is wearing a headset and must be able
: to tap into lines more or less at random. Each time they touch a line
: carrying a 56K connection, they get a loud blast through an earpiece that
: they can't quickly remove. OHSA would like that person to be able to reach
: retirement with their hearing still intact.
<snip>
Well, the proper way to design the things is with limiters...
there is no reason why other equally loud noises can't be coming
down the line.
--
Ian Stirling. Designing a linux PDA, see http://www.mauve.demon.co.uk/
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Edward Rice
In article <34CA1D9D...@ibm.net>,
David Ness <dn...@ibm.net> wrote:
> There may have been some earlier `experiments', but 110baud is
> surely the first speed to gain any fairly wide distribution in the
> computer context. I have a hunch that there were early teletypes
> at even slower speeds, but to the best of my knowledge they were
> never widely used with computers.
FAA weather data was distributed (until oh-too-recently) at 55-baud.
And I think there was a 45-baud version before that, not positive about
that.
Edward Rice
In article <6aej04$h4v$1...@shadow.skypoint.net>,
"George R. Gonzalez" <g...@foundsys.com> wrote:
> That's going back pretty far, but.. Good 'ol Alex Graham Bell
> experimented with the "harmonic telegraph", which I think is basically
> several telegraph signals onto one wire by frequency-division
> multiplexing. This requires modems on both ends. About 1880? Baud
> rate of maybe 1bps?
I thought that multiplexed telegraphy was early Edison. If a good keyer
can manually send about 25 WPM, that's 25x5 characters at roughly four bits
per typical character, or 500 bits (trits, really -- dash or dot or space)
per minute. So, call it about 10-baud.
Isaac
On Wed, 28 Jan 1998, Ron Hunsinger wrote:
[snip]
> So the problem is that at 56K bits per second, the signal can have more
> power than is considered safe for any human ears that might happen to
> listen in on the line. They're trying to get a waiver, or at least
> relaxation, of the guideline, but until then 53K uses all the power that's
> permitted.
[snip]
Please, please let this be a troll....
-Isaac
Ron Hunsinger
In article <000034D07...@mauve.demon.co.uk>, Ian Stirling
<000034D07...@mauve.demon.co.uk> wrote:
> Well, the proper way to design the things is with limiters...
> there is no reason why other equally loud noises can't be coming
> down the line.
But there is a reason -- there's a regulation against it. No one is
permitted to send louder signals through the line.
It's just like walking down the street. They (the powers that be) can
either set a legal limit for how loud automobiles can be, or they can issue
everyone earplugs, or both. Guess which option why took.
Same with the phone company. They could make a regulation against signals
over a certain loudness, or they could spend a small fortune putting
limiters not only in all their own equipment (to protect their own
personell) but also in all the other equipment out there (to protect them
from lawsuits), or they could do both.
Putting sound-limiting circuits on all existing equipment would be
exhorbitant. Even if they put such limiters on the equipment they use
internally (and for all I know they've already done that), they still need
some regulatory limit to protect them from lawsuits. The cutoff was
probably arrived at more or less ad hoc, but it was set before 56K had
entered the scene, and happens to be just too low to permit 56K.
The cutoff could be raised. The risk of hearing damage isn't all or
nothing, and maybe a somewhat higher cutoff would still be safe enough.
But it can't be raised arbitrarily. The additional risk (if any) has to be
assessed and weighed against the benefits. That's what the modem makers are
hoping will happen, but it won't happen overnight or without a lot of
discussion and hearings and studies.
-Ron Hunsinger
anborg
Edward Rice wrote:
>
> In article <34CA1D9D...@ibm.net>,
> David Ness <dn...@ibm.net> wrote:
>
> > There may have been some earlier `experiments', but 110baud is
> > surely the first speed to gain any fairly wide distribution in the
> > computer context.
I have been away and missed some of this thread. However, there seems to
be a problem here. Teletype systems never used modems. These were
successors to wire telegraphy and used DC. Since it was possible to send
telegraph signals by telegraph key and sounder at 45-50 wpm, the
starting point was what was then called 45 wpm.
Best regards,
Art Borg
Ian Stirling
Isaac <is...@pobox.com> wrote:
: On Wed, 28 Jan 1998, Ron Hunsinger wrote:
: [snip]
:> So the problem is that at 56K bits per second, the signal can have more
:> power than is considered safe for any human ears that might happen to
:> listen in on the line. They're trying to get a waiver, or at least
:> relaxation, of the guideline, but until then 53K uses all the power that's
:> permitted.
: [snip]
: Please, please let this be a troll....
Nope, it's true.
--
Ian Stirling. Designing a linux PDA, see http://www.mauve.demon.co.uk/
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"I am the Emperor, and I want dumplings." Austrian Emperor, Ferdinand I.
John A. Limpert
On Sun, 01 Feb 1998 17:56:18 -0500, anborg <anb...@eagle.seed.net.tw>
wrote:
>I have been away and missed some of this thread. However, there seems to
>be a problem here. Teletype systems never used modems. These were
>successors to wire telegraphy and used DC. Since it was possible to send
>telegraph signals by telegraph key and sounder at 45-50 wpm, the
>starting point was what was then called 45 wpm.
Some Teletype systems did use modems. The 60 mA (later 20 mA) current
loop interface was just used as the local interface to the modem.
Current loops don't work too well with radios or AC coupled voice lines.
With the right sort of modem you could put a voice and teletype data
signal on a single phone line (speech plus in NASA jargon) or multiplex
a bunch of teletype data signals onto a single voice channel. The first
computer terminal that I ever used was a KSR-28 Teletype with a built-in
Bell FSK modem.
--
John A. Limpert
jo...@Radix.Net
Edward Rice
In article <34D4FD...@eagle.seed.net.tw>,
anborg <anb...@eagle.seed.net.tw> wrote:
> ... Teletype systems never used modems...
Well, I've used Teletype-brand terminal devices that communicated at
110-baud, and they had modems connected which we used to dial the system we
wanted to use. Maybe your experience was different.
jmfb...@ma.ultranet.com
comm wires were expensive and required localitity. Our system
(installed 1970) used a PDP-8/I that had a bank of dial-ins.
That way anybody on campus who had the pleasure of "owning"
a terminal could call in and log into the system. (I think
I have the details right, but it was a long time ago.)
Now these terminals had [what was then called] acoustic couplers
where one used a regular phone and connected the thing you hold
in your hand to the acoustic coupler, making sure that the rubber
surrounded each end completely, else one had noise on the line
causing disasters.
/BAH
/BAH
Ian Stirling
Ron Hunsinger <hns...@sirius.com> wrote:
: In article <000034D07...@mauve.demon.co.uk>, Ian Stirling
: <000034D07...@mauve.demon.co.uk> wrote:
:> Well, the proper way to design the things is with limiters...
:> there is no reason why other equally loud noises can't be coming
:> down the line.
: But there is a reason -- there's a regulation against it. No one is
: permitted to send louder signals through the line.
Oh, there is a regulation?
that does not strike me as a particularly good reason not to fit
limiters.
--
Ian Stirling. Designing a linux PDA, see http://www.mauve.demon.co.uk/
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Among a man's many good possessions, A good command of speech has no equal.