Woof! On Tue, 07 Oct 2008 13:30:15 -0400, M. Ranganathan <[EMAIL PROTECTED]> wrote:
> What is the difference between : > Detect T38 on CED > -- and -- > Detect T38 on PRE-AMBLE ? CED is the 2100 Hz tone the recieving fax machine emits when it goes to answer a call. It tells the calling FAX machine that a fax machine answered, and not a person. The trouble is CED is the exact same frequency that data modems use (it was actually intended to trigger the disabling of echo cancelation). Some devices like credit card swipers still use dialup, so switching to T.38 on CED might cause the gateway to incorrectly switch to T.38 on data calls. The PREAMBLE is the V.21 training sequence the two Fax modems send to each other to exchange capabilities. This is different from data modem tones (well, not if you still use 300 baud modems) so it is much safer to trigger on. It takes longer to get to PREAMBLE (both sides have to realize the other can hear them), so it might just be a timing thing that it didn't work. --Woof! _______________________________________________ sipx-dev mailing list [email protected] List Archive: http://list.sipfoundry.org/archive/sipx-dev Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-dev
