ECMA TR 87

From Open CSTA

A technical report on CSTA (or User Agent CSTA - uaCSTA). A few good diagrams explaining how things work.

It is important to note that telephones need not support uaCSTA directly - the PBX should support some kind of CSTA or at worst an API for controlling the PBX functions and for receiving telephony events. A uaCSTA gateway/proxy can then convert these and transport the messages to a CSTA-Application.