<s>
A	O
terminal	B-Protocol
adapter	I-Protocol
or	O
TA	O
is	O
a	O
device	O
that	O
connects	O
a	O
terminal	O
device	O
–	O
a	O
computer	O
,	O
a	O
mobile	O
communications	O
device	O
,	O
or	O
other	O
–	O
to	O
a	O
communications	O
network	O
.	O
</s>
<s>
In	O
ISDN	B-Protocol
terminology	O
,	O
the	O
terminal	B-Protocol
adapter	I-Protocol
connects	O
a	O
terminal	O
(	O
computer	O
)	O
to	O
the	O
ISDN	B-Protocol
network	O
.	O
</s>
<s>
The	O
TA	O
therefore	O
fulfills	O
a	O
similar	O
function	O
to	O
the	O
ones	O
a	O
modem	B-Application
has	O
on	O
the	O
POTS	O
network	O
,	O
and	O
is	O
therefore	O
sometimes	O
called	O
an	O
ISDN	B-Protocol
modem	I-Protocol
.	O
</s>
<s>
The	O
latter	O
term	O
,	O
however	O
,	O
is	O
partially	O
misleading	O
as	O
there	O
is	O
no	O
modulation	B-Application
or	O
demodulation	B-Device
performed	O
.	O
</s>
<s>
There	O
are	O
devices	O
on	O
the	O
market	O
that	O
combine	O
the	O
functions	O
of	O
an	O
ISDN	B-Protocol
TA	I-Protocol
with	O
those	O
of	O
a	O
classical	O
modem	B-Application
(	O
with	O
an	O
ISDN	B-Protocol
line	I-Protocol
interface	O
)	O
.	O
</s>
<s>
These	O
combined	O
TA/modems	O
permit	O
connections	O
from	O
both	O
ISDN	B-Protocol
and	O
analog-line/modem	O
counterparts	O
.	O
</s>
<s>
In	O
addition	O
,	O
a	O
TA	O
may	O
contain	O
an	O
interface	O
and	O
codec	B-General_Concept
for	O
one	O
or	O
more	O
analog	O
telephone	O
lines	O
(	O
aka	O
a/b	O
line	O
)	O
,	O
allowing	O
an	O
existing	O
POTS	O
installation	O
to	O
be	O
upgraded	O
to	O
ISDN	B-Protocol
without	O
changing	O
phones	O
.	O
</s>
<s>
Terminal	B-Protocol
adapters	I-Protocol
typically	O
connect	O
to	O
a	O
basic	B-Protocol
rate	I-Protocol
interface	I-Protocol
(	O
S0	B-Protocol
,	O
sometimes	O
also	O
U0	B-Protocol
)	O
.	O
</s>
<s>
On	O
the	O
terminal	O
side	O
,	O
the	O
most	O
popular	O
interfaces	O
are	O
RS-232	O
serial	O
and	O
USB	B-Protocol
;	O
others	O
like	O
V.35	O
or	O
RS-449	O
are	O
only	O
of	O
historical	O
interest	O
.	O
</s>
<s>
Devices	O
connecting	O
ISDN	B-Protocol
to	O
a	O
network	O
(	O
e.g.	O
</s>
<s>
Ethernet	O
)	O
commonly	O
include	O
routing	B-Protocol
functionality	O
;	O
while	O
they	O
technically	O
include	O
a	O
TA	O
function	O
,	O
they	O
are	O
referred	O
to	O
as	O
(	O
ISDN	B-Protocol
)	O
routers	B-Protocol
.	O
</s>
<s>
In	O
mobile	O
networks	O
,	O
the	O
terminal	B-Protocol
adapter	I-Protocol
is	O
used	O
by	O
the	O
terminal	O
equipment	O
to	O
access	O
the	O
mobile	O
termination	O
,	O
using	O
AT	B-Device
commands	I-Device
(	O
see	O
Hayes	B-Device
command	I-Device
set	I-Device
)	O
.	O
</s>
<s>
In	O
2G	O
(	O
such	O
as	O
GSM	O
or	O
CDMA	B-Protocol
)	O
,	O
the	O
terminal	B-Protocol
adapter	I-Protocol
is	O
a	O
theoretically	O
optional	O
while	O
in	O
3G	B-Architecture
(	O
such	O
as	O
W-CDMA	O
)	O
,	O
the	O
terminal	B-Protocol
adapter	I-Protocol
is	O
mandatory	O
and	O
is	O
part	O
of	O
the	O
mobile	O
termination	O
.	O
</s>
<s>
In	O
the	O
automation	B-Application
industry	O
,	O
a	O
terminal	B-Protocol
adapter	I-Protocol
is	O
a	O
passive	O
device	O
that	O
converts	O
a	O
connector	O
like	O
the	O
8P8C	O
(	O
RJ-45	O
)	O
modular	B-Architecture
connector	I-Architecture
or	O
9	B-Protocol
pin	I-Protocol
D-Sub	I-Protocol
into	O
a	O
terminal	O
block	O
to	O
facilitate	O
wiring	O
.	O
</s>
<s>
It	O
is	O
often	O
used	O
when	O
daisy	B-Application
chain	I-Application
wiring	O
is	O
necessary	O
on	O
a	O
multi-node	O
serial	O
communication	O
network	O
like	O
RS-485	O
or	O
RS-422	O
.	O
</s>
