I am working on CCM 5.0 and Cisco IP Phone 7961. I have a problem at locations that when my enduser place a call to a particular IP Phone and when call is connected,end user can hear my voice but i cannot hear the voice of end user. Here is nothing related to Mute button. This problem occurs in few locations and all network IP Phones going good. Please suggest something what is wrong here as this can be major issue,and Protocol i m using is SCCP.Please ask anything related to this query that you need to solve this proble.