I have a small PBX in my office with some SPA921 & SPA942. I have the following problem.
Whenever I place a call through my ISDN line I cannot hear the far-end ring back tone. However when I use x-lite or my iPhone's SIP software everything runs smooth. I checked the admin guide on CISCO site and on page 147 it is written:
"The call progress tone pass-through feature lets you hear call progress tones (such as ringing) that are generated from the far-end network."
However I cannot find such option in my IP phones, neither any other information on both admin/user guides.
Any help is appreciated.