In order to meet the needs of security monitoring, various devices of the system (matrix, hard recorded decoder) Data Interface RS-485 mode, the data in this format interface advantages of a long transmission distance, load capacity, and can be composed of four wire full-duplex communication bus, online any two devices can achieve two-way communication, and four-wire RS-422 bus can only achieve the main, two-way communication between the machine can not be a slave. The disadvantage is that there is a make to end, was the form of three-state, to bring about instability and even "stuck" phenomenon to the communication. If you can not communicate (out of control), the following aspects should find out the reasons:

(1) detecting the presence of the control signal output RS-485 port with a multimeter AC 10V files predictive controller (matrix, hard recording), to see whether the control signal output.

(2) Judgment that HDMI  Extender over fiber of RS-485 interface is normal, if the UA-B voltage is zero is considered abnormal.

PTZ parades can not control, this phenomenon is caused by two reasons: a) RS-485 port A + B-reversed; serious b) the system impedance does not match.