We have a remote office of about 10 users tying back to a corporate office. We have a CTX100 at the remote office and CTX670 at the corporate connected over the internet with T-1 connections at both offices. The quality over the connection is often bad.

We have experimented with a toshiba IPT1020 single VoIP phone at the remote office and the quality is much better. Is there something fundamentally different about the communication used by the two?

Shared bandwidth is usually the problem. Make sure the protocol is set to G.729 and jitter buffer is set high enough, 40 should be ok.