.
.
QMD Install manual D06400210010G PTZ Dome Camera
26
one to another by the software in the camera.
5.5
RS485 Network and Impedance
Transmission distances of RS485 Bus
The 0.56mm (AWG#24) twisted pair or higher grade wires are recommended for
data transmission cable
The maximum theoretical transmitting distances, for the AWG#24, are as follows:
Baud Rate
Maximum Transmitting Distance
2400 Bps
1800m
4800 Bps
1200m
9600Bps
800m
If user selects thinner cables, or installs the dome in an environment surrounded by
strong electromagnetic interference, or connects lots of equipment to the RS485
bus, the maximum transmitting distance will decrease. To increase the maximum
transmitting distance, do the opposite way, i.e. use thicker or more gauged wire and
keep the cable away from the interference source.
Connection and terminator resistor
The RS485 requires daisy-chain connection among the equipments. There must be
terminator resistors for impedance matching (typically 120 ohms, within the range
from 90 to 250 ohms). Terminators are to be located at both ends of each RS-485
net.
120Ω
120Ω
1#
2#
3#
4#
32#
. . . . .
120Ω
1#
2#
3#
31#
120Ω
D
A+
B-
A+
B-
. . . . .
. . . . .
Main controller
