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Teardown Of A 50 Year Old Modem

A Livermore Data Systems acoustically coupled modem from 1965 or thereabouts (in a wooden case).

 

https://hackaday.com/2019/03/29/teardown-of-a-50-year-old-modem/

 

Definitely pretty cool.

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Re: Teardown Of A 50 Year Old Modem

A Solid find if I do say so myself

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Re: Teardown Of A 50 Year Old Modem

I am a bit unclear as to what one did with a modem in 1965.

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Re: Teardown Of A 50 Year Old Modem


@amishgenius wrote:

I am a bit unclear as to what one did with a modem in 1965.


Connected a remote terminal to a stat mux on a timeshare system.

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Re: Teardown Of A 50 Year Old Modem

Yup - that's how you accessed Mainframes if you weren't in the same building (or same floor) as the IBM 360 or whatever.   LANs didn't exist yet and Direct Attach only went so far, so you needed a Modem to operate remotely.      Was also used for Teletype machines for sending Western Union Telegrams, News feeds (AP and UPI), sending data between remote sites - basically any time you needed to send ASCII messages long distances.

Jim

 

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Re: Teardown Of A 50 Year Old Modem

So it basically replaced the telegraph?

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Re: Teardown Of A 50 Year Old Modem

Sure, but then went beyond that to interactive computing with mainframes

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Re: Teardown Of A 50 Year Old Modem


@amishgenius wrote:

So it basically replaced the telegraph?


Originally, yes.   The first "teleprinter" was actually invented in the 1850s, and used to send messages between locations at up to 2000 words per minute - way faster than any telegraph could do.   But they were insanely complex, being mostly mechanical - used things like spinning motorized disks to encode the characters.   It wasn't till 1874 when Emile Baudot invented the idea of encoding characters as 5-bit codes (that's where the name Baud comes from) that this became practical.  In 1901 it was expanded to add things like a Carriage-Return and Line Feed to make it useful for sending formatted text rather than just a stream of characters.   During the early 1900s through the 1920s they kept making improvements in the system, but it's first big system use in the US was for sending real-time information by the FAA in 1928 for weather and flight data - by 1938 the FAA had a network covering 48 states with 20,000 miles of wire.

 

But with the advent of the direct switching telephone system (rotary dials and stepper relay switches) it made sense to use that network rather than dedicated cabling, so they came up with ways to encode the characters as different audio tones which is what a modem does.   Different coding schemes made things faster and faster (although I still had radio stations using 110 Baud teletypes for AP and UPI and network news feeds in 1980 on dedicated current-loop wiring from the phone company) up to the 56K modems many of us remember which used comp[lex trellis-encoding schemes to increase the throughoput of normal traffic - you could actually go faster with synchronous modems, but most users didn't use them - we used them to relay real-time data from moving vehicles on the AMPS cell system on one project I was involved with trying to fix the NorTel Cell System we ran at USWest in the early 90s - synchronous modems were actually the norm in the phone company and are still used for some things today like the stutter-dial tone system to indicate you have voice messages.   The first dedicated Internet DIA connection I ever used was a 14.4K modem on UUNET in 1991 on a USR modem, ran the whole company on that ...

Jim

 

" How can anyone trust Scientists? If new evidence comes along, they change their minds! " Politician's joke (sort of...)
"Humans are allergic to change..They love to say, ‘We’ve always done it this way.’ I try to fight that. "Admiral Grace Hopper, USN, Computer Scientist
"It's not Rocket Science! - Oh wait, Actually it is... "NASA bumper sticker
"Just because you can do something doesn't mean you should."my mantra in the Programming classes I used to teach once upon a time...
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Re: Teardown Of A 50 Year Old Modem


@eejimm wrote:

It wasn't till 1874 when Emile Baudot invented the idea of encoding characters as 5-bit codes (that's where the name Baud comes from) that this became practical.


I remember building baudot to ASCII converters (wire-wrapping and 7400-series TTL IC's) for ASR-33's when I was in high school.

 

TV newsrooms in Los Angeles still had teletype (rip and read, anyone?) network feeds in 1984.  There was at least one in the IBC for the 1988 Seoul Olympics.  We probably had 200 channels of stat muxes there, tied back to LA, NY, and London over dedicated satellite DS3s.

 


The first dedicated Internet DIA connection I ever used was a 14.4K modem on UUNET in 1991 on a USR modem, ran the whole company on that ...


We had a 56k DDS connection to NSFnet at our little dialup ISP 1990 ($3k per month, and running BGP on a Cisco 3000).

 

We sold dedicated 9.6 connections to business using Rockwell NetHoppers.

 

Fun times...