Almost every DVR has the ability to control a multitude of devices using the RS485 protocol. RS485 uses 2 wires to send and receive data to and from these devices. All the devices in an RS485 “network” are connected in parallel with one another. This is a very simple form of communication and relies mainly on the address that is given to each device.
The most common type of device that would be controlled in a security surveillance environment is a PTZ camera. Each PTZ camera on the system must be given a unique identification number. The method of setting this number varies from camera to camera, but normally this is accomplished either by setting a switch on the camera or through the on-screen display or OSD. At this point, you should also take note of the baud rate of the PTZ and the protocol that the PTZ uses (Usually Pelco-D).
Once each PTZ camera is given a unique ID, then the DVR can be configured. Each camera on the DVR that will be controlled will have settings that need to be configured. Just match up these settings with the settings that are configured in the camera. At this point, you should be able to control your PTZ.
There are many other types of devices that can be controlled using RS485. The setup is identical for those devices as well.