
Teardown of a 50-Year-Old Modem - peter_d_sherman
https://hackaday.com/2019/03/29/teardown-of-a-50-year-old-modem/
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C1sc0cat
Steve Garcia in BYTE (1983) had a DIY acoustically coupled modem ($20 in parts
)

I was (in the UK) sorely tempted to change a couple of components and get our
electronics shop to build a batch for a project we where doing to avoid the
huge GPO tax £300 for answer and £650 for answer origionate.

All Illegal of course - though that didn't stop us hacking the modems we did
buy to have variable gain.

For information we brought 6 modems (more than my salary at the time)

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keithpeter
UK 1976 I was doing a computer science O level at the local technical college
(Wednesday afternoon release from my school). There was a 19" rack modem with
accoustic coupler on the front and a dial to dial the number. That was
connected to a teletypewriter. We did some BASIC 'interactive' programming
(the main projects used coding sheets).

The system was vulnerable to thunder storms I remember (line noise). All good
fun.

~~~
C1sc0cat
I rember my first Job (based at Cranfield Uni) and we where a long way away
from the Exchange - Some times you had to whistle into the acoustic coupler to
get the carrier to pickup then quickly put the hand set in.

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jandrese
I wonder why the acoustic coupler was removed?

Eyeballing the pictures there is a lot of corrosion in there. It would
probably be difficult to bring this guy back to life, and even if you did it's
probably 300 baud or so.

~~~
jacquesm
300 would be quite amazing out of that. More like 75/75 for TTY connection.

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VectorLock
This makes me miss good swap meets. The MIT Swap has just been guys in vans
selling plastic trash for the last couple years.

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csours
Look at the big transformer, I was thinking "audio", and sure enough, it's an
acoustic coupled modem, as in "set the phone on the modem"

[https://en.wikipedia.org/wiki/Acoustic_coupler](https://en.wikipedia.org/wiki/Acoustic_coupler)

~~~
pwg
If you are referring to the large transformer clearly visible in the first
photo at the top, that is most likely the AC mains transformer that supplies
power to the modem. This device would have been built before the days of
switching power supplies, and linear power supplies (esp. 50 year old ones)
often begin with a step down transformer of about that size

~~~
tyingq
Guessing this board is the bridge rectifier and DC voltage divider that comes
right after the transformer:
[https://hackadaycom.files.wordpress.com/2019/03/pwr2.jpg](https://hackadaycom.files.wordpress.com/2019/03/pwr2.jpg)

~~~
pwg
That was my guess as well, given the four diodes on the right edge.

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iheartpotatoes
A tiny bit misleading: yes it was a teardown, but I was hoping we'd see a
discussion of the circuits, like the guy that built the analog video game
console a few weeks ago. Still cool tho.

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ngcc_hk
Only saw coupler in books and in war games the movie. Use digital modem Hayes
command etc already. Sad he did not do it. Nice to see how it works.

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SmellyGeekBoy
The modem itself is certainly interesting but the author's tone is very
condescending. Who is Hackaday's target audience, anyway?

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wanderingjew
Nerds. Who think they're smarter than everyone else. It's like Hacker News.
The tone really fits the audience well.

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kemonocode
"The probability of knowing what an acoustically coupled modem looks like is
inversely proportional to knowing what Fortnite is"

I happen to know about both, really. All I can see is a bitter boomer talking
down to anyone born from the mid-eighties onward. (The actual article is fine,
but that sentence sticks out like a sore thumb and makes the rest seem sour)

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peter_d_sherman
"The probability of knowing what an acoustically coupled modem looks like is
inversely proportional to knowing what Fortnite is"

...And yet, the author of the article seems to know what both are...
paradoxically... <g>

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empath75
Inversely proportional does not mean there is no overlap :)

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peter_d_sherman
Excellent Point!

I stand corrected!

:)

