incomming call suddenly disconnected in UC520 platform

i have following IP telephony system currently installed in
our office :
sometimes if outside person call us the reception IP phone ring
when he wants to pickup the call he does not hear any body
and the call disconnecting
please advice
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It might be connectivity issue between IP telephone and the server it is using for registration. Check with the IP telephoy provider and explain him about the problem you are facing. And also check your internet connectivity for any drops packet.
ashraf2002Author Commented:
actually all IP phones currently installed within our local LAN and the call manager in our local LAN too
In that senario Extension to extension or you can say calls in LAN will work fine but if some one calls you from outside then they will first hit the IP Telephony server ie.. VOIP server and for that outside calls you need to check what I mentioned above for call drops and quality.
And also remember if other person is all using some IP telephony service then same thing applies to him as well to have good communication. some time everything willl be fine on your side but problem on the outsider who is calling. Its all dependent on internet connection on both side.
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ashraf2002Author Commented:
we faced the problem with outside callers , they are call us on our FXO lines there is not any internet
connection between us
Defination of IP telephony: IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user. Much of IP telephony focuses on that challenge. For More click the link below,,,sid186_gci212388,00.html 
 IP Telephony Basics, 
ashraf2002Author Commented:
dear sir
i know the IP telephony basics i am CCNA voice certified i need a solution for my problem is that possible ?
best regards
just issue the command 'supervisory disconnect signal' under the fxo port and test this.This command may  be varying depends up on the router platform model


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IP Telephony

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