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2.2 Device connection
2.2.1 RS485 connection
Note: When the 485 bus high-frequency signal is transmitted, the signal wavelength is shorter than the transmission
line, and the signal will form a reflected wave at the end of the transmission line, which will interfere with the original
signal. Therefore, it is necessary to add a terminal resistor at the end of the transmission line so that the signal does not
reflect after reaching the end of the transmission line. The terminal resistance should be the same as the impedance of the
communication cable, the typical value is 120 ohms. Its function is to match the bus impedance and improve the
anti-interference and reliability of data communication.
2.2.2 Relay output connection