Nitsuko is ok, it used to be Tie communications which was number three in telephone system sales at one point. Now, it is owned by NEC America I believe.
Anyway, for dropped calls, my first two questions are always:
1. when it goes away, does the line key light go out or not?
2. does it happen on calls in, calls out or both?
If the light goes out, the line is likely being disconnected from the KSU itself. Either it is dropped by the telco, or you may have a hardware/trunk problem. If the light stays on and you lose audio, then you more than likely have an internal hardware problem (trunk card, trunk port, station card, station port, station, wire)
Hope that helps It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com