American Fibertek Net I/O N-664 - Manual (Page 9)

9
Connecting RS485 four-wire
To connect to a serial port in RS485 4-wire mode, you will need a DB9 connector wired
as indicated. Four connections will need to be made for the two data transmit lines and
the two data receive lines. Do not make any other connections to any other pins on the
DB9 connector.
Connecting RS485 two-wire
To connect to a serial port in RS485 4-wire mode, you will need a DB9 connector wired
as indicated. Two pairs of pins on the DB9 will need to be bridged together. Two
connections will then need to be made to the bridged pins for the two bidirectional data
lines. Do not make any other connections to any other pins on the DB9 connector.