Although there is no theoretical limit to the maximum of PBX's CAM can support there are processing limits that you will encounter. If these are large PBX's I would recommend you purchase a CAM license for each PBX and then use access each CAM license via your browser. Additionally, if the PBX's being utilized only support a serial connection then the CAM software will need to be either located at the same location as the phone system or may require a hardware buffer. Since hardware buffers usually cost significantly more than CAM I would recommend you install an additional license of the CAM software at these locations.