RS-485 Cable 16
RS-485 Cable
Appendix 2
Appendix 2.1 General
RS-485 industrial buses are half-duplex communication buses whose characteristic impedance
is 120Ω. Its maximum load is 32 payloads (including drivers and receivers).
Appendix 2.2 RS-485 Transmission Distance
When using 0.56 mm (24AWG) twisted pair, depending on different baud rate, the maximum
theoretical transmission distances are listed. See Appendix table 2-1.
Appendix table 2-1 Theoretical maximum transmission distance
Baud rate
Maximum transmission distance
2400 bps
1800 m
4800 bps
1200 m
9600 bps
800 m
The maximum transmission distance might be reduced in the following conditions; otherwise,
maximum transmission distance will be increased.
When thinner communication cables are used;
The Camera is used in places with intense electromagnetic interference;
Too many devices are connected to the RS-485 cable.
Appendix 2.3 Frequently Occurred Problems
Customers tend to connect devices as the way displayed in Appendix figure 2-1. In this
condition, the terminal resistance must be connected to the two devices whose cable length is
the largest among all the devices (in Appendix figure 2-1, cable length between 1# and 15# is
the largest). However, this connection manner dose not comply with the RS-485 industrial bus
standard. As a result, problems like signal reflection and anti-interference capability reduction
might occur.
Appendix figure 2-1 The common manner of connecting devices
