<s>
In	O
telecommunications	O
,	O
an	O
acoustic	B-Device
coupler	I-Device
is	O
an	O
interface	B-Protocol
device	O
for	O
coupling	O
electrical	O
signals	O
by	O
acoustical	O
means	O
—	O
usually	O
into	O
and	O
out	O
of	O
a	O
telephone	O
.	O
</s>
<s>
The	O
link	O
is	O
achieved	O
through	O
converting	O
electric	O
signals	O
from	O
the	O
phone	O
line	O
to	O
sound	O
and	O
reconvert	O
sound	O
to	O
electric	O
signals	O
needed	O
for	O
the	O
end	O
terminal	O
,	O
such	O
as	O
a	O
teletypewriter	O
,	O
and	O
back	O
,	O
rather	O
than	O
through	O
direct	O
electrical	B-Protocol
connection	I-Protocol
.	O
</s>
<s>
In	O
Australia	O
,	O
until	O
1975	O
the	O
PMG	O
,	O
a	O
Government	O
monopoly	O
,	O
owned	O
all	O
telephone	O
wiring	O
and	O
equipment	O
in	O
user	O
premises	O
and	O
prohibited	O
attachment	O
of	O
third	O
party	O
devices	O
,	O
and	O
while	O
most	O
handsets	O
were	O
connected	O
by	O
600	B-Protocol
series	I-Protocol
connectors	I-Protocol
,	O
these	O
were	O
rare	O
in	O
Australia	O
so	O
imported	O
equipment	O
could	O
not	O
be	O
directly	O
connected	O
in	O
any	O
case	O
,	O
despite	O
the	O
general	O
electrical	O
compatibility	O
.	O
</s>
<s>
This	O
decision	O
enabled	O
the	O
proliferation	O
of	O
later	O
innovations	O
like	O
answering	O
machines	O
,	O
fax	O
machines	O
,	O
and	O
modems	B-Application
.	O
</s>
<s>
His	O
acoustic	B-Device
coupler	I-Device
is	O
known	O
as	O
the	O
Weitbrecht	O
Modem	B-Application
.	O
</s>
<s>
The	O
Weitbrecht	O
Modem	B-Application
inspired	O
other	O
engineers	O
to	O
develop	O
other	O
modems	B-Application
to	O
work	O
with	O
8-bit	O
ASCII	O
terminals	O
at	O
a	O
faster	O
rate	O
.	O
</s>
<s>
Such	O
modems	B-Application
or	O
couplers	O
were	O
developed	O
around	O
1966	O
by	O
John	O
van	O
Geen	O
at	O
the	O
Stanford	O
Research	O
Institute	O
(	O
now	O
SRI	O
International	O
)	O
,	O
that	O
mimicked	O
handset	O
operations	O
.	O
</s>
<s>
One	O
would	O
dial	O
the	O
computer	O
system	O
(	O
which	O
would	O
have	O
telephone	O
company	O
datasets	O
)	O
on	O
one	O
's	O
phone	O
,	O
and	O
when	O
the	O
connection	O
was	O
established	O
,	O
place	O
the	O
handset	O
into	O
the	O
acoustic	O
modem	B-Application
.	O
</s>
<s>
Since	O
the	O
handsets	O
were	O
all	O
supplied	O
by	O
the	O
telephone	O
company	O
,	O
most	O
had	O
the	O
same	O
shape	O
,	O
simplifying	O
the	O
physical	O
interface	B-Protocol
.	O
</s>
<s>
A	O
microphone	B-Application
and	O
a	O
speaker	O
inside	O
the	O
modem	B-Application
box	O
would	O
pick	O
up	O
and	O
transmit	O
the	O
signaling	O
tones	O
,	O
and	O
circuitry	O
would	O
convert	O
those	O
audio	O
frequency-shift	O
keying	O
encoded	O
binary	O
signals	O
for	O
an	O
RS232	O
output	O
socket	O
.	O
</s>
<s>
The	O
practical	O
upper	O
limit	O
for	O
acoustic-coupled	O
modems	B-Application
was	O
1200	O
baud	O
,	O
first	O
made	O
available	O
in	O
1973	O
by	O
Vadic	O
and	O
1977	O
by	O
AT&T	O
.	O
</s>
<s>
1200	O
baud	O
endpoints	O
became	O
widespread	O
in	O
1985	O
with	O
the	O
advent	O
of	O
the	O
Hayes	O
Smartmodem	O
1200A	O
,	O
though	O
it	O
used	O
an	O
RJ11	O
jack	O
and	O
was	O
not	O
an	O
acoustic	B-Device
coupler	I-Device
.	O
</s>
<s>
Such	O
devices	O
facilitated	O
the	O
creation	O
of	O
dial-up	O
bulletin	B-Application
board	I-Application
systems	I-Application
,	O
a	O
forerunner	O
of	O
modern	O
internet	O
chat	O
rooms	O
,	O
message	B-Application
boards	I-Application
,	O
and	O
e-mail	O
.	O
</s>
<s>
Usually	O
,	O
a	O
standard	O
telephone	O
handset	O
was	O
placed	O
into	O
a	O
cradle	O
that	O
had	O
been	O
engineered	O
to	O
fit	O
closely	O
(	O
by	O
the	O
use	O
of	O
rubber	O
seals	O
)	O
around	O
the	O
microphone	B-Application
and	O
earpiece	O
of	O
the	O
handset	O
.	O
</s>
<s>
A	O
modem	B-Application
would	O
modulate	O
a	O
loudspeaker	O
in	O
the	O
cup	O
attached	O
to	O
the	O
handset	O
's	O
microphone	B-Application
,	O
and	O
sound	O
from	O
the	O
loudspeaker	O
in	O
the	O
telephone	O
handset	O
's	O
earpiece	O
would	O
be	O
picked	O
up	O
by	O
a	O
microphone	B-Application
in	O
the	O
cup	O
attached	O
to	O
the	O
earpiece	O
.	O
</s>
<s>
Acoustic	B-Device
couplers	I-Device
were	O
sensitive	O
to	O
external	O
noise	O
and	O
depended	O
on	O
the	O
widespread	O
standardization	O
of	O
the	O
dimensions	O
of	O
telephone	O
handsets	O
.	O
</s>
<s>
Once	O
they	O
were	O
made	O
legal	O
and	O
the	O
AT	O
command	O
set	O
became	O
standard	O
for	O
modems	B-Application
,	O
direct	O
electrical	B-Protocol
connections	I-Protocol
to	O
telephone	O
networks	O
rapidly	O
became	O
the	O
preferred	O
method	O
of	O
attaching	O
modems	B-Application
,	O
and	O
the	O
use	O
of	O
acoustic	B-Device
couplers	I-Device
dwindled	O
.	O
</s>
<s>
Acoustic	B-Device
couplers	I-Device
were	O
still	O
used	O
until	O
at	O
least	O
the	O
late	O
1990s	O
by	O
people	O
travelling	O
in	O
areas	O
of	O
the	O
world	O
where	O
electrical	B-Protocol
connection	I-Protocol
to	O
the	O
telephone	O
network	O
is	O
illegal	O
or	O
impractical	O
.	O
</s>
<s>
Many	O
models	O
of	O
TDDs	O
(	O
Telecommunications	O
Device	O
for	O
the	O
Deaf	O
)	O
still	O
have	O
a	O
built-in	O
acoustic	B-Device
coupler	I-Device
,	O
which	O
allow	O
more	O
universal	O
use	O
with	O
pay	O
phones	O
and	O
for	O
911	O
calls	O
by	O
deaf	O
people	O
.	O
</s>
<s>
An	O
acoustic	B-Device
coupler	I-Device
(	O
a	O
Novation	O
CAT	O
300	O
baud	O
model	O
)	O
is	O
prominently	O
shown	O
early	O
in	O
the	O
1983	O
film	O
WarGames	B-Application
,	O
when	O
character	O
David	O
Lightman	O
(	O
portrayed	O
by	O
actor	O
Matthew	O
Broderick	O
)	O
places	O
a	O
telephone	O
handset	O
into	O
the	O
cradle	O
of	O
a	O
film	O
prop	O
acoustic	O
modem	B-Application
to	O
accentuate	O
the	O
act	O
of	O
using	O
telephone	O
lines	O
for	O
interconnection	O
to	O
the	O
developing	O
computer	O
networks	O
of	O
the	O
period	O
—	O
in	O
this	O
case	O
,	O
a	O
military	O
command	O
computer	O
.	O
</s>
<s>
The	O
earliest	O
major	O
motion	O
picture	O
depicting	O
an	O
acoustic	B-Device
coupler	I-Device
was	O
probably	O
the	O
1968	O
Steve	O
McQueen	O
film	O
Bullitt	O
.	O
</s>
