Earlier Power Macintosh and Quadra computers have the Ethernet icon, as in Figure 1, but with a different style of port. This is the Apple Attachment Unit Interface (AAUI) port. This type of port requires a transceiver, a small box that adapts the AAUI to the type of cabling used (such as RJ-45). On Power Macintosh computers that came with both an AAUI and RJ-45 port, you can use only one at a time.
Check out this page with various AAUI transievers. Asanté made one and farallon as well. In the olden days, this was great cause you could get a transiever that either went to RJ45 10t or 10base T (coaxial cable.. a few old copier/printers etc.. used this and some really old networks).