[comp.sys.apple] //GS serial interface question

mcgurrin@MITRE.ARPA.UUCP (05/11/87)

The Technical Intro to the //GS states that the serial ports are RS-422, 
configured to be compatible with RS-232.  Can someone explain to me how
this works, since 422 requires balanced signals while 232 does not?
Does it use normally unused pins of a 232 connection for the opposite 
direction of balanced lines when connected  to a 422 device?  How does the
//GS interface compare with the new EIA-530 standard?  What are the differences?
Any information on this or leads would be greatly appreciated.  Thanks!