AUI stands for Attachment Unit Interface.
An AUI signal is analog digital.... :-)
Okay, what I mean is that there are pairs of wires that carry what
I believe is a "difference" signal representing the ones and zeros.
The MAU is what translates the AUI signals to the voltage levels
used on an Ethernet cable, which is *mostly* digital, except when
a collision occurs, where the voltage may drift to an intermediate
analog voltage for a few microseconds. It is the job of the MAU
to realize that this intermediate voltage *is* a collision, it then
drives the CI pair (if I recall correctly) on the AUI cable, which
is the "collision indication" pair. Because it is an analog voltage
detection, which varies by how many 1's and 0's collide, it is not
a "clean" way to detect collisions, which is just one of the reasons
why twisted-pair Ethernet (StarLAN 10) is so much nicer, since it
does *digital* detection of collisions, by seeing when two ports
are active at the same time on a hub. End of lesson 102....
Please read The Standard Disclaimer regarding information found in these pages.
To return to the top of the Corcoran document archives Click Here
If you came here directly from a search engine, and would like to view these pages in the proper frames from the top, Start Here
Or start at the very top of Mike Corcoran's home page