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-   -   possible to use a modem (rj-11) to talk to a serial device? (http://www.linuxquestions.org/questions/linux-hardware-18/possible-to-use-a-modem-rj-11-to-talk-to-a-serial-device-4175451061/)

/dev/random 02-21-2013 02:01 AM

possible to use a modem (rj-11) to talk to a serial device?
 
I was wondering if it were possible to talk to a serial device with a 56k modem?

As far as I can tell, both use UART, both are serial devices, so I don't see why this wouldn't work? If I got or made a RJ-11 to Serial adaptor would this actually work through minicom?


The reason why I ask is I have a notebook that still has a modem that is fully functional in linux and I also have a fully managed dell switch (powerconnect 5324) instead of buying a USB to Serial adaptor (that always never works correctly) would it be possible to interface with my switch using my 56k modem?

TobiSGD 02-21-2013 06:42 AM

A modem converts digital data to analog signals. RS-232 does not use analog signals, so this won't work.

/dev/random 02-21-2013 01:06 PM

Hey TobiSGD,
Thanks for giving that lil peice of information.

I have read somewhere that older external modems used a db25 cable that can interface with the AUX port on some cisco/dell hardware thats why I assumed this would be possible in the first place, The other reason why I thought this would work is because I have used two modems before with no line, just hooked up directly to each other to transfer files back in the older days. Since a modem can be set to be either listen or call (DCE or DTE) I assumed this would work.

But it makes sense if the modem itslef converts the signals to another format then it wouldnt work.

Thanks anyways

jefro 02-21-2013 03:55 PM

The old way was a serial port to a modem, then modem over POTS to a modem then to serial. You can still do that but you'd need to setup up a faux POTS line.

To send digital data over a phone line one converts marks and spaces (plus and minus) to audio tone packages. That is how a modem like a 56K works.


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