Just when I was ready to work on the deployment of several hundred Asterisk SIP phones, I bumped into a serious potential show stopper: an echo.
I went to Astricon and attended the Echo Session. I also happen to know some (not a lot) about impedance matching, etc.
My problem is mainly related to the DTMF digits when my users call an IVR system, from a SIP phone to a PSTN IVR.
Would some of you folks out there (preferably knowledgeable) please dial into the Boston Verizon voice mail number from your SIP phone:
1-617-491-0012and then leave a message, for instance, in my voice mail:
617-576-2545(you don't have to leave anything) In fact, you will probably not be able to leave any message because the DTMF digits will not be recognized.
These are my settings:
Asterisk 1.2.0-beta2 Sipura 2100 Cisco AS-5300
A colleague called from his Linksys digital hardphone and was able to leave me a message (i.e. the DTMF digits were recognized by Verizon), but then when he tried from a Sipura ATA he failed.
It looks like it is worth purchasing the whole telephone (as opposed to a ATA+phone combination) if you want to prevent echo.
I tried changing the "FXS Port Input Gain" and "FXS Port Output Gain" from the -3 default to -2 and -1, but no luck.
TIA,
-Ramon F Herrera