Apple GeoPortThe back panel of all Power Macintosh models contain two I/O ports for serial telecommunication data.
Apple IIc Serial PortThis is the Apple implementation of the RS-232c interface for the Apple IIc (not IIc+) computer
Apple Macintosh RS-422It´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.
Apple Macintosh SerialThis connector is present on Macintosh 128K, 512K, and 512K enhanced.