[asterisk-dev] Listening to a remote dialtone on a DAHDI/PRI has been suppressed in 1.6.1 ?

[Pavel Troller]

Hi!
  I'm new on this list, let me introduce myself shortly first.
  I'm a switching systems expert, working for one of major operators in Czech
Republic as well being an associated professor at Czech Technical University,
lecturing the same subject. My main focus is concentrated on "big" switches,
like Siemens EWSD or Nortel CallServer 2000, as well as some PBXes, especially
Ericsson MD110/MX1, Siemens HiPath etc. I'm working with Asterisk mainly as my
hobby, but I'm also using it in my work, currently we run a Meetme conference
and Customer Announcement System on Asterisk at our telco.
  And now, my first question: I've upgraded my Asterisk from 1.6.0.9 to 1.6.1.0
and I've found that I cannot listen to the dialtones from remote exchanges on 
overlapped outgoing calls over DAHDI/PRI (i.e. Dial(DAHDI/g1) without a number,
with empty SETUP sent). 
  I've reviewed chan_dahdi.c and I've found, that the following change:

        case SIG_PRI:
        case SIG_BRI:
        case SIG_BRI_PTMP:
        case SIG_SS7:
                /* We'll get it in a moment -- but use dialdest to store pre-setup_ack digits */
                p->dialdest[0] = '\0';
+               p->dialing = 1;
                break;

around line 2710 is causing this. I've commented this line out and I have my
dialtones back.
  I would like to ask, why this change has been made and whether it is 
necessary. I'm using overlap mode dialling very often and I (and my users too)
like to hear the dialtones as we are traversing through our networks :-). Is
there another way to open the audio path immediately, i.e. using some new 
config option, yet unknown to me ? 

  With regards, Pavel Troller