2 Wire RS-485 Half Duplex Pinout
Frequently Asked Questions
Written by Wesley Moore
Updated at April 3rd, 2026
Brand:
- AMX
Models:
- Anything with an RS-485 serial port
Question:
How do you wire a 2 wire RS-485 connection?
Answer:
RS485 half-duplex can use just two wires to communicate with up to 32 device, one at a time. Each device has the ability to turn off its output drivers, so only the one device that is linking to the host outputs a signal on its TX lines. Terminating Resistors (RT) are connected across the ends of the A B wires.
RS485 allows multiple devices (up to 32) to communicate at half-duplex on a single pair of wires, plus a ground wire at distances up to 1200 meters (4000 feet). "Four-wire" networks have one master port with the transmitter connected to each of the "slave" receivers on one twisted pair.
