Fax modem?

Leon Stringer leon.stringer at ntlworld.com
Fri Nov 2 19:37:20 CET 2007

Patrick Smears wrote:
> On Fri, 2 Nov 2007, Jonathon Suggs wrote:
>> Just FYI, I'm about 97% positive that the ability to send faxes over GSM
>> is dependent upon the carrier.  In the case of T-Mobile (USA) you have
>> to call customer support and have them enable it.  I believe that there
>> is also a monthly charge as well (maybe ~$5/month).
> It certainly is carrier-dependent. In the UK, O2 consumer tariffs do not
> support it at all; their business tariffs do, but you have to ask them to
> enable it specifically (and then they give you separate fax & data
> numbers), though there is no extra charge for this. Not sure about the
> other UK operators.
>> Other carriers might be different, and it might "just work" but at least
>> here stateside then are going to nickel and dime you as much as they
>> can.  Besides, doesn't that require some out of band signalling (or
>> something similar that isn't in the base GSM spec)?
> AFAIK in GSM, fax calls are similar to data calls, where the network does
> the work of decoding the modem tones, so you get the full 9600bps of data
> (rather than having to try to decode the tones from GSM-encoded sounds!).  
> The network knows to do this based on either signalling from the calling
> end (eg if the call originates from a GSM phone), or based on the called
> number (eg if it is from a landline). This is why O2 give you the separate 
> numbers for fax/data - without them, you can make data calls but not 
> receive them, and you couldn't receive faxes (in fact you can't send them 
> either, but I don't know of a reason for this).
>> OT, does anybody actually still use fax machines?
> I occasionally get asked how to use the one in the office, so I assume 
> peope are still using it :-)
> -P

Thanks for all of your replies. I don't actually have a device as we'd 
need to be fairly confident it would work to trial one.

Yes fax capability is dependent on carrier (we're using O2 in the UK) 
but as I stated it needs to have support in the handset too. We've 
researched this extensively and can't find a handset currently on the 
market which works as a fax modem (even if they work as a data modem).

Our application is in the healthcare field: we have ECGs which can 
transmit the readings as a fax. This is done from a Bluetooth adapter in 
the ECG which is paired to a handset. This works quickly, synchronously 
and reliably which are all essential. Even if there were a non-fax 
solution which met these needs (MMS?) only fax transmission is supported 
by the ECG device. Any update is years away.

Our handsets are getting old and breaking, and we want to increase the 
number of ECG devices but we're stuck on the handset front. So I 
wondered if anyone could tell me whether this would work with the 
devices you're working on:

  - Definitely (i.e. you know for certain that the device will act as a 
Bluetooth fax modem)

  - Likely (i.e. all the support should be in the device but you've 
never seen it work)

  - Unlikely

  - Definitely not

Thanks again for your input so far,


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