[Tilt, TyTN II, MDA Vario III General] FactionOne:
It looks like there's good progress being made on this one then :)

OK, just some theory for my 2p's worth...

I'm not sure wireless plans should pose too much of an issue, I know things might be different in Belgium but here in the UK I don't know of too many drastic issues using 'analogue' modems over GSM. Of course all digital cellular traffic is exactly that, but in a voice call there's A/D and D/A at each end - for the simple fact that when I call my mum, I say "Hello, Mum!" and not 1100110101011100110111101110111110010111 (I know I'm being daft, but you see my point). The element of CSD not being available on service plans would I guess only come into play if you wanted your cellular provider to be your access layer to a network, namely the internet - in that way your GSM device would use a WAP access number to 'dial modem(s)' at your cellular provider and connect it to the internet via their (computer) network. That of course is what's largely unavailable with cellular telcos these days, as of course GPRS and UMTS connectivity have replaced that.

What you're actually trying to achieve though is simply a point-to-point 'analogue' call. Picture this - you have two human beings, who happen to have the amazing talent of being able to speak 'faxish' - If person A dials person B's number and screeches down the phone, so long as person B can hear the screeching and is able to screech back down the line, there's no reason the two can't negotiate and use an 'analogue' modem (/fax) connection.

In simple terms the problem with CSD not being available leads to the remote device (your modem/handset etc) dialling a number to negotiate a connection with an 'analogue' modem which simply isn't there anymore. Of course that problem isn't evident in this scenario though - your plan isn't for the cellular provider to give you access to a data network, you simply want to use them as transport between your modem and a similar device elsewhere - both completely accessible by a 'voice' number.

So, so long as you can make voice calls on your cellular plan, there is no real reason for your cellular service to bring your plan to an abrupt end.

This is all backed up by the fact that the TAM company I'm a field engineer for uses GSM modems in some of its communication. In some situations we have a GSM device which is for all intents and purposes a GSM phone with 'automatic answer' enabled, with an 'analogue' modem on its mic and speaker (it's not exactly that in electrical terms - but that's a fair description of what happens in effect). We dial into its voice number from a modem in the office and we have a data connection for our own proprietary data-link. In other equipment, the same thing happens in reverse - we have a GSM communications box containing a modem that, each night, automatically dials out from a GSM device to what is essentially a voice number with a modem sat at the end waiting to negotiate a similar connection.

There are no special service plans involved - they use standard SIM cards with standard packages - the only special deal in our case is that the 'outbound dialling' remote devices are prevented from dialling any number other than our modem lines, but this is done by our request to the provider(s) - we have Vodafone and Orange SIMs in use in this way, but I've no reason to expect any other provider wouldn't be able to deliver the same.

So, it all comes down to the device itself - back in the WM2003 and WM5 days 'tethered internet' seemed simply to be the provision of a modem, and it was just the choice of specific modem commands that caused it to route to an active GPRS/UMTS session - via a virtual (my term, not HTCs) dial-up connection.

This is all just theory to help back up the HyperTerminal examples above. I can't help wondering what would happen if you just set-up a standard dial-up modem connection from within XP using the HTC USB modem as the selected device, dialling (for example) 0845 665 3000 - which is an 'open' dial-up number from http://www.adial.co.uk/ - I can't help thinking that you'd get a PPP TCP/IP connection without any headaches. If that's the case there's no reason you couldn't use the same method to dial any modem to negotiate a similar connection, or indeed HyperTerminal to do anything less 'standard'...

Regards,

Rob.