i need to be notified when i call some one and he already have other call.so i need to know that i am on waiting
FYI, you need to mention what you're using (CUCM, CME, etc) and not just your problem, or what you want to do to get assistance.
I'll assume CUCM, there is no way to do what you're asking, the phone will ring for any call that arrives to the line as long as it's below the busy trigger.
There is no way to provide some other ring back tone or cadence for this.
The only option would be to have the phone do NOT ring, send the call to CUC, and then play the busy greeting to let them know you're on a call.
i have CUCM 10.5.there is no way that the caller have screen notification that th eother part have call
No, CUCM provides no way to do what you're asking.
The only option, would be to try presence enabled directories, but that would only work for users who call from within the enterprise, external callers would not see this.
Or if you have Jabber, see the status there.