The short answer is no, not every phone system. The intelli-CTi server has certainly extended the number of phone systems we can support including certain hosted VOIP systems etc. However, some vendors do not offer a suitable interface (API) for us to provide integration. There are some phone system systems, notably Asterisk based ones that provide a simple API, however, it lacks certain functions making it impossible to fully support it.
Our Telephone System Compatibility Guide is updated regularly with the latest status, but we always strongly recommend a full test of the system before ordering intelli-CTi using the product trial download.