Office-based CSD/USSD Server?



It’s possible to have 2 GSM modems dial one another to set up a data connection. If there is a central office, with, say, 100 satellite modems, having the office modem dial each satellite modem (or vice-versa) in turn is not a good solution.

If the satellites could dial a number for which there could be numerous (virtual) lines then that would be an advantage. A VOIP phone system would appear to fit the bill for this. Are there any standard products that provide such a dial-up service that would allow numerous remote GSM modems to connect to an office LAN using CSD?



Yes, that is the fundamental scalability problem with any circuit-switched arrangement!

I guess you should look to how ISPs do (or did) this to support dial-up customers…

In principle, it should be possible for the networks to provide this sort of thing as an “interworking function” - but I suspect they’d rather you used GPRS these days…


ISDN-30, etc,… :question:

Edit - something like this: :question:

“120-Port, V.92/V.110/V.90/ISDN, Dial-Up Remote Access Server (RAS)”


Eek! $10,000 for one of those!


There’s always a catch! 8)


This might be the right sort of device - supporting “modem over IP”:


I guess another possibility could be to use USSD for inbound messages.

" You need to approach every operator and get a SMPP account opened with the operator"

Has anyone done this?

Is there a guide anywhere on how to install a handler on the mobile network to catch them?


I guess that’s the real killer?!

Could you not just use SMS?


Yes but SMS messages can sometimes be queued. For hours.


True - possibly even days?


Example: viewtopic.php?f=11&t=4499&p=18133#p18133


Fixed link: