Planet Technology DVR-471 - Manual (Page 21)

4/16-ch H.264 Digital Video Recorder
3.4 RS-485 interface
RS485 is use for connect to external device, such as keyboard or PTZ camera.
3.4.1 RS-485 Menu Setup
Enter LINK -> RS485 menu to set the parameters of RS-485 device which connected with
DVR (The parameters must the same with the device).