LT Security LTD3446HT - Manual (Page 12)

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Alarm input connection 1-N.C.
b) Sensor adopt N.O. output contact
Alarm input connection 1-N.O.
B、 Alarm output connection ：
Alarm output connection
2.3.3 RS-485/RS485 connection
Host have one standard RS-485/232 port, pin definition please refer to Pic.3. RS485 is used to control PTZ
decoder and camera, RS232 is used to debugging software and other communications expanding.
Host builds in many PTZ/camera protocols, it can connect 4 PTZ decoders/cameras at the same time, and each
channel corresponds to one. Default PTZ decoder/camera decoder is same as its channel number.