Planet Technology CAM-ISD48 用户手册

4.5  RS-485 Network and Impedance 

 

Transmission distances of RS-485 Bus 

The 0.56mm (24AWG) 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 with strong 

electromagnetic interference, or connects lots of equipment to the RS-485 bus, the 

maximum transmitting distance will be decreased. To increase the maximum 

transmitting distance, do the contrary, i.e. use thicker wire and keep the cable away 

from the interference. 

 

The RS-485 standard requires a daisy-chain connection among the equipments. 

There must be termination resistors of proper impedance (typically 120 ohms, 

within the range from 90 to 250 ohms) at both ends of the connection.

   

120Ω

120Ω

1#

2#

3#

4#

32#

 

120Ω

1#

2#

3#

31#

120Ω

D

A+

B-

A+

B-

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Main controller

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User’s manual 

                                                                                                     

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