I have an RS422 or RS485 device with serial terminals labeled TXA, TXB, RXA and RXB. My other RS22/RS485 devices have terminals labeled TX+, TX-, etc or DOUT+, DOUT-, etc. Do I connect TXA to RX+ or RX-?

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In RS422/RS485 A is equivalent to - and B is equivalent to +. A typical 4-wire connection would look like this:

RS485              RS485  
device 1           device 2
TXA----------------RX- or DIN-
TXB----------------RX+ or DIN+

RXA----------------TX- or DOUT-
RXB----------------TX+ or DOUT+

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[Originally Published On: 06/29/1999 09:03 AM]