AVUE G55IR-WB36N – Outdoor 36X Long Range IR PTZ - Manual (Page 43)

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Characteristics of Rs485 Bus
Transmission distances of Rs485 Bus
Connection and termination resistor
As specified by Rs485 standard, Rs485 Bus is of
half-duplexed data transmission cables with chara-
cteristic impedance as 120 . The maximum load
capacity is 32 unit loads (including main controller
and controlled equipment.)
When user selects the 0.56mm(24AWG)twist-
ed pair wires as data transmission cable, the maxi-
mum theoretical transmitting distance are as foll-
ows:
If user selects thinner cables, or installs the PTZ
in an environment with strong electromagnetic
interference, or connects lots of equipment to the
Rs485 Bus, the maximum transmitting distance w-
ill be decreased. To increase the maximum transm-
itting distance, do the contrary.
The Rs485 standards require a daisy-chain Conn-
ection between the equipment. There must be ter-
mination resistors with 120 (as the picture 10-2.1).
Please refer to picture 10-2.2 for simple connection.
D should not exceed 7m.
Ω
Ω
“ ”
10. 4 Rs485 Bus Basic Knowledge
120Ω
1# 2# 3# 4# 32#
Picture 10-4.1
120Ω
120Ω
1# 2# 3# 4# 32#
D
A+
B-
A+ B-
Picture 10-4.2
120Ω
2400BPS
4800BPS
9600BPS
1800m
1200m
800m
Baud rate Max distance
19200BPS 600m
Picture10-4.3
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The connection of 120 termination resistor: Ω
40
Connection mode for 120 resistance of equipment
terminal. Setting connection of terminal resistance
120 in the base cover. (Refer to Picture 10-4.3):
Default of factory (No.8 digit of SW2 is set
on code switch)No.8 digit of SW2 is set
on
code switch if needed to connect 120 resistance.
“ OFF”
“ ON”
Ω
Ω
Sw1 Sw2
Setting of 120 resistance Ω
Appendix