<s>
The	O
Attachment	B-Protocol
Unit	I-Protocol
Interface	I-Protocol
(	O
AUI	O
)	O
is	O
a	O
physical	O
and	O
logical	O
interface	O
defined	O
in	O
the	O
original	O
IEEE	O
802.3	O
standard	O
for	O
10BASE5	O
Ethernet	O
and	O
the	O
previous	O
DIX	O
standard	O
.	O
</s>
<s>
The	O
physical	O
interface	O
consists	O
of	O
a	O
15-pin	O
D-subminiature	B-Protocol
connection	O
that	O
provides	O
a	O
path	O
between	O
an	O
Ethernet	O
node	O
's	O
physical	O
signaling	O
and	O
the	O
Medium	B-Protocol
Attachment	I-Protocol
Unit	I-Protocol
(	O
MAU	B-Protocol
)	O
,	O
sometimes	O
also	O
known	O
as	O
a	O
transceiver	O
.	O
</s>
<s>
An	O
AUI	O
cable	O
may	O
be	O
up	O
to	O
long	O
,	O
although	O
frequently	O
the	O
cable	O
is	O
omitted	O
altogether	O
and	O
the	O
MAU	B-Protocol
and	O
medium	B-Protocol
access	I-Protocol
controller	I-Protocol
MAC	B-Device
are	O
directly	O
attached	O
to	O
one	O
another	O
.	O
</s>
<s>
On	O
Ethernet	O
implementations	O
without	O
separate	O
MAU	B-Protocol
and	O
MAC	B-Device
,	O
the	O
AUI	O
is	O
omitted	O
.	O
</s>
<s>
AUI	O
connectors	O
became	O
rare	O
beginning	O
in	O
the	O
early	O
1990s	O
when	O
computers	O
and	O
hubs	B-Protocol
began	O
to	O
incorporate	O
the	O
MAU	B-Protocol
,	O
particularly	O
as	O
the	O
10BASE-T	B-Protocol
standard	O
became	O
more	O
common	O
and	O
use	O
of	O
10BASE5	O
(	O
thicknet	O
)	O
and	O
10BASE2	O
(	O
thinnet	O
)	O
declined	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
Fast	B-Protocol
Ethernet	I-Protocol
the	O
AUI	O
became	O
obsolete	O
,	O
and	O
was	O
replaced	O
by	O
the	O
Media	B-Protocol
Independent	I-Protocol
Interface	I-Protocol
(	O
MII	O
)	O
.	O
</s>
<s>
A	O
modified	O
form	O
using	O
a	O
smaller	O
connector	O
called	O
the	O
AAUI	B-Protocol
was	O
introduced	O
on	O
Apple	B-Device
Macintosh	I-Device
computers	I-Device
in	O
1991	O
,	O
and	O
its	O
use	O
discontinued	O
in	O
1998	O
.	O
</s>
<s>
An	O
AUI	O
connector	O
is	O
a	O
DA-15	B-Protocol
(	O
D-subminiature	B-Protocol
)	O
.	O
</s>
<s>
It	O
has	O
a	O
sliding	O
clip	O
in	O
place	O
of	O
the	O
thumbscrews	O
normally	O
found	O
on	O
a	O
D-connector	B-Protocol
to	O
hold	O
two	O
connectors	O
together	O
.	O
</s>
<s>
This	O
clip	O
permits	O
the	O
MAU	B-Protocol
and	O
MAC	B-Device
to	O
be	O
directly	O
attached	O
to	O
one	O
another	O
even	O
when	O
their	O
size	O
and	O
shape	O
would	O
preclude	O
the	O
use	O
of	O
thumbscrews	O
.	O
</s>
