Arch Linux

cryptopsii

Member

Registered: 2014-01-06

Posts: 10

tinkering with old 56k modem

Hi everyone,
Recently I was thinking about a way to replace a cisco SPA2102, a voip box with 2 RJ45 and RJ11 plug
with (of course) voip functionnality.

An old P4 box would be powerful enough for this and so much more but...
what about the RJ11? Problem I still need those because everyone in my house
would rather use a cordless phone connected to a base, which use a regulare phone line (RJ11).

Looking at even older computer I realised those old pci 56K modem did have an RJ11.
Now I was thinking, is there a way to somehow get the same functionnality of the spa2102
with a PC + 56K modem?

Something like asterisk on a linux machine would that care of the voip part,
but what about the interface between the PBX server , the modem and the phone?
I'm almost sure you can actually connect a modem to a phone, but how send audio
to the phone? Or when you open the phone, the modem would need to quickly talk
to the PBX server.  That seem very tricky.

And searching for keyword that involve Modem + phone is a nighmare on google...
What do you guys think?

progandy

Member

Registered: 2012-05-17

Posts: 5,280

Re: tinkering with old 56k modem

You might want to search for asterisk, fxs, gateway, 56k modem, ...
If I understand it correctly, you need an FXS port which supplies power, so your 56k modem won't work (FXO port, receives power)

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R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: tinkering with old 56k modem

I'd say not to bother with old 56k modems, at least not the ones you could buy dirt cheap, those are most probably what is called winmodems, all the processing was done in software so I guess you will not have much luck there.

I don't even know if there are any linux drivers for those, at best they will probably show up as a soundcard (mono in + mono out). Then there is also what progandy said, the "normal" phone line provides some power to the phone, even cordless phones which have their own power source might still rely on the power supplied by the phone line for signaling.

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R00KIE
Tm90aGluZyB0byBzZWUgaGVyZSwgbW92ZSBhbG9uZy4K

cryptopsii

Member

Registered: 2014-01-06

Posts: 10

Re: tinkering with old 56k modem

Okay, thanks.
FXS is what I will be looking for, a "real" modem
and FXO are the "fake" aka winmodem using a dsp
where everything is done in software.

I guess ill familiarize myself with asterisk first,
then ill see... if I still care about this.

progandy

Member

Registered: 2012-05-17

Posts: 5,280

Re: tinkering with old 56k modem

Okay, thanks.
FXS is what I will be looking for, a "real" modem
and FXO are the "fake" aka winmodem using a dsp
where everything is done in software.

That's not quite right. FXS and FXO have nothing to do with that. a "real" modem also has FXO ports. End devices like phones and computer modems normally connect to the telephone net, so they have an FXO port.
An FXS port provides the power and the connection to the rest of the world for your end devices. The phone socket on your wall is such an FXS port.
Maybe this will help
http://www.3cx.com/pbx/fxs-fxo/
http://en.wikipedia.org/wiki/Foreign_ex … cations%29
http://www.dceexpress.com/FXS_FXO_Discussion.htm

Last edited by progandy (2014-01-07 04:17:50)

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