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dial-in server

hello I would like to make a dial-in server, not for internet but for a Linux terminal i want to run it on a raspberry pi running rasbian I have been looking for ages I found mgetty but I can't  find a tutorial

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On 3/5/2019 at 9:50 AM, thomasdouwes said:

hello I would like to make a dial-in server, not for internet but for a Linux terminal i want to run it on a raspberry pi running rasbian I have been looking for ages I found mgetty but I can't  find a tutorial

Not sure how complicated you were wanting to get, but you could always connect a serial modem to the PI, something like this.

It uses an "enhanced" AT command set. I used something similar to this once with success, its worth a look, you might need a dedicated line if you want to use auto answer.

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well I misplaced my devboard, if I find it, ill post a pic. The exact one I used was the "ch1724" made by a company called "Cermetek", this is a link to the website, and this is a link to the documentation / typical application.

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On 3/8/2019 at 6:24 AM, CodeNova said:

Not sure how complicated you were wanting to get, but you could always connect a serial modem to the PI, something like this.

It uses an "enhanced" AT command set. I used something similar to this once with success, its worth a look, you might need a dedicated line if you want to use auto answer.

yes I have a usb to serial cable connected to the modem I would like it to be something like this or this also I still have a copper line

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22 hours ago, thomasdouwes said:

yes I have a usb to serial cable connected to the modem I would like it to be something like this or this.

So originally I suggested the "ch1724", for what I was doing, the modem module was very appealing. I was able to dial out with a custom terminal program, I felt like I had more control over the modem, and I didn't need any drivers. Since you have a usb modem (I'm assuming you got it to work with the PI), you might have luck with 'mgetty'. From what I have been reading, getting it set up should be doable. I'll post some links I found about the subject, hopefully you will find them useful.

PI modem setup

shell server

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3 hours ago, thomasdouwes said:

Thanks this worked minus the inittab which i do not have but a friend helped me use system ctl which works now to try and build an acustic coupeler so I can dial in over my mobile e.g http://eric-ode.tripod.com/acoustic_coupler.htm and https://youtu.be/uQqWHLZjOjA

That sounds like a really cool project, what did you have in mind?

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I want to build an acoustic coupler so I can put a retro handset for my mobile on it and dial into my raspberry pi dial in server

 and get a shell so I can, ssh into other computers, use a command line browser, or whatever else you can do from a command line.

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5 hours ago, thomasdouwes said:

I want to build an acoustic coupler so I can put a retro handset for my mobile on it and dial into my raspberry pi dial in server

 and get a shell so I can, ssh into other computers, use a command line browser, or whatever else you can do from a command line.

Neat, how did you plan on doing it? I was toying around with some NOS (new old stock) chips once, they worked pretty well. One in particular I think you should look at is the 74VHC943N or the MC145442B.

The 74VHC943N is a bit dated, but if you look hard enough you can still find them for sale, I found mine from a gray market reseller.

20190312112147.jpg.245957a0bee7e864d6c1c8251254a7a6.jpg

In the datasheet the manufacture provides an applications circuit for an acoustic coupler (74VHC942N).

image.png.59f4be3488508443f91eaf45b2695db7.png

That being said, I think there might be an easier solution to your problem, its called minimodem it 'uses the computers sound-card to encode/decode modem audio tones'. The software actually works pretty well, I've tested it a few times myself. By using your computers sound card, you could conceivably just connect your cellphone to your computers audio interface with just an aux cable, no need for an acoustic coupler.

So your setup might look something like this...

laptop->aux cables->Cellphone>> ----- POTS (plain old telephone service) ---->>Serial modem->raspberry PI->command-line goodness

Sadly after doing a bit of research on your behalf, I don't think you can expect speeds faster than 300bps due to the digital compression of audio on most modern cellphones.

 

Let me know how everything works out, and post an update, I would really enjoy seeing your progress.

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 300bps is fine but 1 my cell or mobile mic port is a mic port, not a line in and 2 you need Linux im running windows but I can use a VM also I tried this but with Skype and it did not work but the 73VHC942N looks good I was going to use old corded phone connected to a 9 volt battery and to a modem like this

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Is this recent? I don't see the year marked and haven't seen this happen in years, I am interested to see what you can do with this! Interesting project! I was researching an old tech term and found this page. My workbench is cluttered with pi and arduino projects.. trying to help build the smart future with old concepts. Do you document your projects to share with others? I'll need my other computer to update you guys with some projects I'm working on. I can't log into Trello right now but I'll share it soon, it might help with some innovative engineering ideas. Last week I made a wifi enabled thermoelectric generator system used as a sensor and simultaneously a remote temperature controller. 

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8 hours ago, sknate said:

Is this recent?

Yeah, its only about a week old. I would be interested to see your project. As far as documentation goes, if the occasion calls for it. This really is a 'computer' forum though. I joined in the hopes there would be more 'hobby electronics', sadly, its limited.

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