My DVR has a rs232 port and the spec says "RS-232 connector (ISP. For RD control)". What is that used for? I am looking for a way to connect a pc as a controller for the PTZ cameras. I want to use remote access to a pc next to the dvr for veiwing and controlling the cameras and backing up the recordings when the dvr is full. Have been looking for a pc application for controlling the ptzs but have not had any luck with that.