User manual

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CharacteristicsofRs485Bus
TransmissiondistancesofRs485Bus
Connectionandterminationresistor
AsspecifiedbyRs485standard,Rs485Busisof
half-duplexeddatatransmissioncableswithchara-
cteristicimpedanceas120.Themaximumload
capacityis32unitloads(includingmaincontroller
andcontrolledequipment.)
Whenuserselectsthe0.56mm(24AWG)twist-
edpairwiresasdatatransmissioncable,themaxi-
mumtheoreticaltransmittingdistanceareasfoll-
ows:
Ifuserselectsthinnercables,orinstallsthePTZ
inanenvironmentwithstrongelectromagnetic
interference,orconnectslotsofequipmenttothe
Rs485Bus,themaximumtransmittingdistancew-
illbedecreased.Toincreasethemaximumtransm-
ittingdistance,dothecontrary.
TheRs485standardsrequireadaisy-chainConn-
ectionbetweentheequipment.Theremustbeter-
minationresistorswith120(asthepicture10-2.1).
Pleaserefertopicture10-2.2forsimpleconnection.
Dshouldnotexceed7m.
Ω
Ω
“”
10.4Rs485BusBasicKnowledge
120Ω
1#2#3#4#32#
Picture10-4.1
120Ω
120Ω
1#2#3#4#32#
D
A+
B-
A+
B-
Picture10-4.2
120Ω
2400BPS
4800BPS
9600BPS
1800m
1200m
800m
Baudrate
Maxdistance
19200BPS
600m
Picture10-4.3
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Theconnectionof120terminationresistor: Ω
40
Connectionmodefor120resistanceofequipment
terminal.Settingconnectionofterminalresistance
120inthebasecover.(RefertoPicture10-4.3):
Defaultoffactory(No.8digitofSW2isset
oncodeswitch)No.8digitofSW2isseton
codeswitchifneededtoconnect120resistance.
“OFF”
“ON”
Ω
Ω
Sw1
Sw2
Settingof120resistanceΩ
Appendix