Rs485 Bus Faq - Qvis APOHD-PTZ20 User Manual

In this situation, we recommend RS485 distributor. This device can turn a star type connection into the
connection that conforms to the RS485 bus industry standard, which can avoid the above mentioned problems
and enhance communication reliability. See Figure 10-2.

10.4 RS485 Bus FAQ

Phenomenon Possible Reasons

Speed dome
can run self-
diagnosis but

I cannot
control it.



I can control
the speed

dome but the
movement is
not smooth


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Figure 10-2
Host address (baud rate) and
speed dome address (baud
rate) do not match;
Positive and negative end of
RS485 Bus are not connected
correctly;
Connection cable is loose；
RS485 Bus connections are cut
off;
RS485 Bus connections are
poor；
One of the RS485 buses is
offline；
The distance between host and
speed dome is too far；
Too many speed domes are
connected in parallel.
Solution

Modify host or speed dome setup ；

Switch RS485 positive end and
negative end；

Fix connection cable firmly；

Replace RS485 Bus.

Connect RS 485 Bus again；

Replace RS485 Bus；

Add terminal matching resistance；

Add RS485 distributor.
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