[Gllug] Modem emulator

[Andrew Back]

On (13:06 10/05/10), Matthew King wrote:
> The scenario:
> 
> Home network's fancy router has a (56k) modem on it plugged directly
> into the phone line (actually it doesn't but the fact that Martin has
> one reminds me that I ought to get one).
> 
> While out, the house's connection to the internet breaks for whatever
> reason. Hoping it isn't the router itself, I pull out my mobile phone,
> dial my modem's number and ... hear screeching because I don't have a
> modem on this end.
> 
> Is there software available which can use the mobile network to send
> modem traffic? Is the codec even capable of it?

I doubt a GSM audio channel will work, as they tend to run at between 6.5
and 13 kbit/s and so the audio is obviously compressed. And IIRC GSM does
stuff like not using the channel when a mobile station is silent, with the
network inserting "comfort noise" so the fixed subscriber doesn't think the
line has gone dead. I'm not sure what modems would make of this.

GSM also has "circuit switched data" (as used mobile IP access pre-GPRS)
which could give you a 9.6k connection, but I'm pretty sure that the fixed
modem would have to be in the GSM network. I could be wrong...

What would be cool is if someone made a SIP enabled "virtual modem
application", that connected over 3G, WiFi or whatever, and then presented a
virtual serial port to which you can attach whatever you like, e.g. a
terminal or PPP.
 
> Alternatively, is there some other way to connect to the home (or some
> other) network when the ultra-reliable-unlike-19th-century-POTS DSL
> fails, other than an outgoing IP-based connection from the router using
> the modem?

Become a licensed radio amateur and set up a VHF/UHF AX.25 node, have 3G at
home, get an Inmarsat or Mobitex terminal, or some feathered friends and RFC
1149.

Cheers,

Andrew

-- 
Andrew Back
mailto:andrew at osmosoft.com
http://carrierdetect.com
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