It's possible to connect RS-232 peripheral to the RS-422 port available on Macintosh computers. Use RXD- as RXD, TXD- as TXD, Ground RXD+, Leave TXD+ unconnected, GPi as CD.
(At the computer)
8 PIN MINI-DIN FEMALE at the computer.
|2||HSKi/CLK||Input Handshake or External Clock|
|3||TXD-||Transmit Data (-)|
|5||RXD-||Receive Data (-)|
|6||TXD+||Transmit Data (+)|
|7||GPi||General Purpose Input|
|8||RXD+||Receive Data (+)|