<s>
A	O
telecommunication	B-Device
control	I-Device
unit	I-Device
(	O
TCU	O
)	O
,	O
line	O
control	O
unit	O
,	O
or	O
terminal	O
control	O
unit	O
(	O
although	O
terminal	O
control	O
unit	O
may	O
also	O
refer	O
to	O
a	O
terminal	O
cluster	O
controller	O
)	O
is	O
a	O
Front-end	B-General_Concept
processor	I-General_Concept
for	O
mainframes	B-Architecture
and	O
some	O
minicomputers	B-Architecture
which	O
supports	O
attachment	O
of	O
one	O
or	O
more	O
telecommunication	O
lines	O
.	O
</s>
<s>
Many	O
of	O
these	O
TCUs	O
can	O
support	O
RS-232	O
when	O
it	O
is	O
required	O
,	O
although	O
there	O
are	O
other	O
serial	B-Protocol
interfaces	O
as	O
well	O
.	O
</s>
