I am working with an SPA8000 that is supplying dialtone to ESTech systems/ESI/IVX pbx phone systems. I have discovered that caller ID information is not being received by what they call their "legacy" or older model pbx's. I have confirmed that caller ID is in fact coming through to my analog test set and also sends the caller ID to an run of the mill caller ID box. I have also verified that the caller ID works properly through the ESI systems on normal AT&T analog lines. The strange thing is that caller ID works on ESI's newer "communication servers". I have spoken with ESI's tech support and have been told that no changes for those parameters have been changed. I also have the latest possible versions of software running on all of the older systems. If anyone on the forums have any suggestions or input on this issue I would greatly appreciate it.