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Frequently Asked Questions
RS232/RS485/RS422 QUESTIONS
14) IS RS422 4-WIRE THE SAME AS RS485 4-WIRE?
Answer: No, they are not. Although electrically similar, the signals are quite different. RS422 must cabled using a minimum of 4-wires (TX+, TX-, RX+, RX-), whereas RS485 can be cabled with a few as 2 wires (T/R+, T/R-) with GND and voltage reference lines added optionally in the RS485 4-wire configuration. Other differences in the standards include (a) RS422 can be operated in full-duplex mode, whereas RS485 is half-duplex, and (b) the nominal minimum input impedance of devices on the networks is not the same, and (c) the data rates possible at different cabling distances are different.
