[asterisk-dev] Proposal for T.38 transparent gateway design in Asterisk

[Lee Howard]

Kevin P. Fleming wrote:
> Klaus Darilion wrote:
>
>   
>> Further, FAXOPT should be allow configure the faxdetection flexible, 
>> e.g. CNG and/or CED tone, incoming or outgoing)
>>     
>
> CED tone is not a reliable discriminator for FAX. CNG tone is, for
> detection of calling FAX machines, and is already supported by
> chan_dahdi (and could easily be supported by the other TDM channel
> drivers as well).

CNG isn't reliable, either.  A faxmodem dialing with ATDT<number>@ will 
not produce CNG, and many fax callers will do this in order to not 
disturb the receiver if they happen to call a human instead of a machine.

Fax detection is not entirely reliable either way ... neither detecting 
CED nor detecting CNG.

Thanks,

Lee.