<s>
GeoPort	B-Device
is	O
a	O
serial	B-Protocol
data	I-Protocol
system	O
used	O
on	O
some	O
models	O
of	O
the	O
Apple	B-Device
Macintosh	I-Device
that	O
could	O
be	O
externally	O
clocked	O
to	O
run	O
at	O
a	O
2	O
Mbit/s	O
data	O
rate	O
.	O
</s>
<s>
GeoPort	B-Device
slightly	O
modified	O
the	O
existing	O
Mac	B-Device
serial	B-Protocol
port	I-Protocol
pins	O
to	O
allow	O
the	O
computer	O
's	O
internal	O
DSP	B-Architecture
hardware	O
or	O
software	O
to	O
send	O
data	O
that	O
,	O
when	O
passed	O
to	O
a	O
digital-to-analog	O
converter	O
,	O
emulated	O
various	O
devices	O
such	O
as	O
modems	B-Application
and	O
fax	O
machines	O
.	O
</s>
<s>
GeoPort	B-Device
could	O
be	O
found	O
on	O
late-model	O
68K-based	O
machines	O
(	O
the	O
AV	O
series	O
)	O
as	O
well	O
as	O
many	O
pre-USB	O
Power	B-Device
Macintosh	I-Device
models	O
and	O
PiPPiN	B-Device
.	O
</s>
<s>
Some	O
later	O
Macintosh	B-Device
models	O
also	O
included	O
an	O
internal	O
GeoPort	B-Device
via	O
an	O
internal	O
connector	O
on	O
the	O
Communications	B-Device
Slot	I-Device
.	O
</s>
<s>
Apple	O
GeoPort	B-Device
technology	O
is	O
now	O
obsolete	O
,	O
and	O
modem	B-Application
support	O
is	O
typically	O
offered	O
through	O
USB	B-Protocol
.	O
</s>
<s>
Early	O
during	O
the	O
development	O
of	O
the	O
Apple	B-Device
Macintosh	I-Device
,	O
Apple	O
engineers	O
decided	O
to	O
use	O
the	O
Zilog	B-Device
8530	I-Device
"	O
Serial	B-Protocol
Communications	I-Protocol
Controller	O
"	O
(	O
SCC	O
)	O
for	O
most	O
input/output	B-General_Concept
tasks	O
.	O
</s>
<s>
Initially	O
the	O
engineers	O
had	O
envisioned	O
using	O
the	O
SCC	O
to	O
support	O
a	O
packet-based	B-Protocol
protocol	O
known	O
as	O
"	O
AppleBus	O
"	O
.	O
</s>
<s>
AppleBus	O
would	O
allow	O
peripheral	O
devices	O
to	O
be	O
plugged	O
into	O
a	O
daisy-chain	B-Application
configuration	O
in	O
a	O
manner	O
surprisingly	O
similar	O
to	O
the	O
modern	O
Universal	B-Protocol
Serial	I-Protocol
Bus	I-Protocol
.	O
</s>
<s>
Team	O
members	O
working	O
on	O
AppleBus	O
quickly	O
shifted	O
gears	O
,	O
producing	O
the	O
LocalTalk	B-Device
system	O
running	O
on	O
the	O
SCC	O
ports	O
rather	O
than	O
AppleNet	O
's	O
plug-in	O
expansion	O
card	O
.	O
</s>
<s>
LocalTalk	B-Device
relied	O
on	O
clocking	O
from	O
the	O
CPU	O
that	O
was	O
divided	O
down	O
to	O
produce	O
an	O
output	O
at	O
roughly	O
230.4kbit/s	O
.	O
</s>
<s>
This	O
allowed	O
the	O
entire	O
system	O
to	O
be	O
run	O
over	O
a	O
simple	O
three-wire	O
connection	O
,	O
or	O
two-wires	O
in	O
the	O
case	O
of	O
PhoneNet	B-Protocol
.	O
</s>
<s>
However	O
,	O
as	O
the	O
SCC	O
had	O
only	O
three	O
bytes	O
of	O
buffer	O
space	O
,	O
it	O
was	O
critical	O
that	O
the	O
ports	O
be	O
read	O
as	O
quickly	O
as	O
possible	O
to	O
prevent	O
a	O
buffer	B-General_Concept
overflow	I-General_Concept
and	O
loss	O
of	O
data	O
.	O
</s>
<s>
This	O
was	O
not	O
an	O
issue	O
for	O
networking	O
protocols	O
,	O
where	O
lost	O
packets	B-Protocol
are	O
assumed	O
and	O
dealt	O
with	O
in	O
the	O
network	B-Protocol
stack	I-Protocol
,	O
but	O
represented	O
a	O
serious	O
problem	O
for	O
RS-232	O
data	O
which	O
had	O
no	O
internal	O
form	O
of	O
flow	O
control	O
in	O
the	O
data	O
stream	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
performance	O
on	O
a	O
Mac	B-Device
Plus	I-Device
was	O
generally	O
limited	O
to	O
about	O
9600bit/s	O
in	O
RS-232	O
mode	O
,	O
and	O
could	O
only	O
reliably	O
maintain	O
half	O
of	O
that	O
if	O
LocalTalk	B-Device
was	O
active	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Apple	O
was	O
aware	O
of	O
these	O
problems	O
,	O
and	O
starting	O
with	O
the	O
Macintosh	B-Device
IIfx	I-Device
they	O
attempted	O
to	O
address	O
them	O
by	O
including	O
two	O
dedicated	O
"	O
Input/Output	B-General_Concept
Processors	O
"	O
(	O
IOP	O
)	O
,	O
customized	O
MOS	B-General_Concept
6502s	I-General_Concept
running	O
at	O
10MHz	O
.	O
</s>
<s>
The	O
IOPs	O
offloaded	O
the	O
low-level	O
driver	O
code	O
from	O
the	O
host	O
CPU	O
,	O
running	O
the	O
floppy	O
disks	O
and	O
serial	B-Protocol
ports	I-Protocol
,	O
only	O
interrupting	O
the	O
CPU	O
when	O
there	O
was	O
data	O
to	O
transfer	O
.	O
</s>
<s>
The	O
IIfx	O
also	O
introduced	O
a	O
DMA	B-General_Concept
mode	O
for	O
the	O
SCSI-bus	O
,	O
but	O
this	O
was	O
not	O
available	O
for	O
use	O
by	O
the	O
IOPs	O
.	O
</s>
<s>
The	O
IOPs	O
also	O
appeared	O
on	O
the	O
Quadra	B-Device
900	I-Device
and	O
Quadra	B-Device
950	I-Device
.	O
</s>
<s>
After	O
the	O
early	O
Quadra	O
machines	O
,	O
Apple	O
started	O
a	O
short-lived	O
experiment	O
including	O
AT&T	O
3210	O
digital	B-Architecture
signal	I-Architecture
processors	I-Architecture
(	O
DSP	B-Architecture
)	O
in	O
the	O
"	O
AV	O
"	O
series	O
machines	O
(	O
the	O
840AV	B-Device
and	O
660AV	B-Device
)	O
.	O
</s>
<s>
The	O
DSP	B-Architecture
was	O
primarily	O
intended	O
to	O
offer	O
audio	O
and	O
video	O
digitization	O
support	O
,	O
accessed	O
though	O
the	O
custom	O
60-pin	O
"	O
Digital	O
Audio/Video	O
"	O
(	O
DAV	O
)	O
port	O
on	O
the	O
rear	O
of	O
the	O
machines	O
.	O
</s>
<s>
DSPs	O
were	O
also	O
commonly	O
used	O
at	O
that	O
time	O
as	O
the	O
basic	O
building	O
block	O
of	O
high-speed	O
modems	B-Application
.	O
</s>
<s>
Using	O
the	O
relatively	O
advanced	O
3210	O
would	O
offer	O
higher	O
performance	O
than	O
existing	O
modems	B-Application
,	O
which	O
used	O
lower-end	O
DSPs	O
,	O
and	O
much	O
better	O
performance	O
than	O
softmodems	B-Device
using	O
the	O
host	O
CPU	O
.	O
</s>
<s>
However	O
,	O
the	O
60-pin	O
AV	O
connector	O
was	O
not	O
suitable	O
for	O
such	O
connections	O
,	O
and	O
users	O
expected	O
to	O
plug	O
"	O
modems	B-Application
"	O
into	O
the	O
modem	B-Application
port	O
.	O
</s>
<s>
Although	O
the	O
existing	O
serial	B-Protocol
ports	I-Protocol
could	O
be	O
adapted	O
to	O
run	O
in	O
"	O
AV	O
mode	O
"	O
in	O
the	O
same	O
fashion	O
that	O
the	O
older	O
versions	O
could	O
run	O
in	O
RS-232	O
or	O
networking	O
mode	O
,	O
the	O
line	O
adaptor	O
required	O
more	O
power	O
that	O
the	O
port	O
could	O
supply	O
.	O
</s>
<s>
Apple	O
solved	O
this	O
problem	O
by	O
adding	O
a	O
9th	O
pin	O
to	O
the	O
existing	O
8-pin	O
Mini-DIN	B-Protocol
connector	I-Protocol
.	O
</s>
<s>
The	O
result	O
was	O
GeoPort	B-Device
.	O
</s>
<s>
In	O
GeoPort	B-Device
mode	O
the	O
SCC	O
was	O
placed	O
in	O
a	O
high-speed	O
mode	O
using	O
external	O
clocking	O
,	O
similar	O
to	O
the	O
earlier	O
high-performance	O
LocalTalk	B-Device
replacements	O
.	O
</s>
<s>
The	O
DSP	B-Architecture
then	O
generated	O
signals	O
and	O
sent	O
them	O
over	O
the	O
serial	O
bus	O
to	O
the	O
adapter	O
,	O
which	O
converted	O
them	O
to	O
analog	O
and	O
amplified	O
them	O
to	O
telephone	O
levels	O
.	O
</s>
<s>
In	O
GeoPort	B-Device
mode	O
,	O
speeds	O
up	O
to	O
2Mbit/s	O
were	O
supported	O
.	O
</s>
<s>
One	O
widely	O
known	O
device	O
to	O
make	O
use	O
of	O
the	O
GeoPort	B-Device
was	O
Apple	O
's	O
own	O
"	O
GeoPort	B-Device
Telecom	O
Adapter	O
"	O
.	O
</s>
<s>
Initially	O
released	O
as	O
the	O
"	O
pod	O
"	O
with	O
the	O
AV	O
Macs	B-Device
in	O
1993	O
,	O
it	O
later	O
became	O
its	O
own	O
separate	O
product	O
in	O
early	O
1995	O
when	O
it	O
was	O
released	O
for	O
PowerPC-based	O
Macintosh	B-Device
machines	O
that	O
did	O
not	O
include	O
AV-related	O
hardware	O
out	O
of	O
the	O
box	O
.	O
</s>
<s>
Apple	O
later	O
incorporated	O
GeoPort	B-Device
lines	O
into	O
an	O
edge	O
connector	O
on	O
the	O
motherboard	O
of	O
certain	O
Mac	B-Device
models	O
known	O
as	O
the	O
Communication	B-Device
Slot	I-Device
,	O
preserving	O
them	O
on	O
the	O
later	O
Communication	B-Device
Slot	I-Device
II	O
.	O
</s>
<s>
Three	O
adaptors	O
would	O
eventually	O
be	O
sold	O
:	O
the	O
original	O
pod	O
,	O
the	O
internal	O
version	O
,	O
and	O
an	O
updated	O
pod	O
known	O
as	O
the	O
GeoPort	B-Device
Telecom	O
Adapter	O
II	O
.	O
</s>
<s>
In	O
practice	O
the	O
GeoPort	B-Device
Adaptors	O
tied	O
up	O
huge	O
amounts	O
of	O
CPU	O
time	O
,	O
and	O
led	O
to	O
performance	O
problems	O
throughout	O
the	O
system	O
.	O
</s>
<s>
SAGEM	O
also	O
introduced	O
an	O
ISDN	B-Protocol
adaptor	O
for	O
GeoPort	B-Device
,	O
the	O
"	O
Planet-ISDN	O
Geoport	B-Device
Adapter	O
"	O
,	O
or	O
SPIGA	O
,	O
which	O
they	O
now	O
sell	O
in	O
a	O
USB	B-Protocol
version	O
.	O
</s>
<s>
Global	O
Village	O
also	O
produced	O
a	O
variant	O
of	O
its	O
compact	O
Teleport	O
Modems	B-Application
for	O
Apple	O
Performas	O
and	O
third-party	O
Mac	B-Device
computers	I-Device
that	O
used	O
the	O
9th	O
pin	O
to	O
supply	O
power	O
,	O
but	O
these	O
were	O
true	O
hardware	O
modems	B-Application
,	O
not	O
GeoPort	B-Device
devices	O
.	O
</s>
<s>
Apple	O
's	O
first	O
two	O
QuickTake	B-Device
digital	O
cameras	O
(	O
100	O
and	O
150	O
)	O
also	O
supported	O
the	O
GeoPort	B-Device
protocol	O
for	O
transfer	O
between	O
the	O
camera	O
and	O
GeoPort-equipped	O
Macintosh	B-Device
computers	I-Device
.	O
</s>
<s>
During	O
the	O
evolution	O
of	O
GeoPort	B-Device
,	O
the	O
telecommunications	O
market	O
was	O
undergoing	O
major	O
changes	O
with	O
the	O
introduction	O
of	O
newer	O
all-digital	O
PBX	B-Device
systems	O
.	O
</s>
<s>
A	O
number	O
of	O
these	O
companies	O
offered	O
some	O
sort	O
of	O
computer	O
telephony	O
integration	O
,	O
although	O
they	O
were	O
all	O
based	O
on	O
their	O
own	O
standards	O
,	O
typically	O
connected	O
to	O
the	O
computers	O
via	O
a	O
serial	B-Protocol
port	I-Protocol
at	O
relatively	O
low	O
speeds	O
.	O
</s>
<s>
Although	O
these	O
signals	O
could	O
have	O
been	O
routed	O
using	O
existing	O
networking	O
standards	O
like	O
Ethernet	O
,	O
most	O
companies	O
used	O
custom	O
systems	O
,	O
like	O
Switch56	B-Device
.	O
</s>
<s>
Apple	O
started	O
an	O
effort	O
to	O
promote	O
GeoPort	B-Device
as	O
a	O
standardized	O
computer	O
interface	O
to	O
PBX	B-Device
systems	O
.	O
</s>
<s>
They	O
envisioned	O
different	O
GeoPort	B-Device
adapters	O
for	O
different	O
back-end	O
systems	O
;	O
a	O
Switch56	B-Device
interface	O
could	O
be	O
used	O
with	O
Northern	O
Telecom	O
systems	O
,	O
while	O
another	O
would	O
be	O
used	O
to	O
connect	O
to	O
the	O
InteCom	O
switches	O
that	O
Apple	O
used	O
.	O
</s>
<s>
Apple	O
claimed	O
that	O
the	O
"	O
same	O
GeoPort	B-Device
phone	O
pod	O
will	O
be	O
able	O
to	O
support	O
TAPI	B-Library
applications	O
on	O
a	O
Windows	O
PC	O
and	O
Telephone	O
Manager	O
applications	O
on	O
a	O
Mac.	O
"	O
</s>
<s>
To	O
connect	O
those	O
systems	O
to	O
the	O
Macintosh	B-Device
,	O
in	O
particular	O
,	O
Apple	O
created	O
the	O
Macintosh	B-Device
Telephony	O
Architecture	O
(	O
MTA	O
)	O
and	O
promoted	O
it	O
as	O
a	O
standardized	O
telephony	O
application	B-Application
program	I-Application
interface	I-Application
.	O
</s>
<s>
The	O
MTA	O
consisted	O
primarily	O
of	O
three	O
parts	O
,	O
the	O
"	O
Telephone	O
Manager	O
"	O
which	O
handled	O
call-control	O
,	O
the	O
"	O
Telephone	O
Tool	O
"	O
that	O
mapped	O
Telephone	O
Manager	O
commands	O
onto	O
specific	O
hardware	O
,	O
and	O
finally	O
a	O
set	O
of	O
telephony-related	O
Apple	B-Operating_System
Events	I-Operating_System
that	O
would	O
allow	O
simple	O
operation	O
from	O
any	O
scripting-aware	O
Macintosh	B-Device
program	O
.	O
</s>
<s>
MTA	O
was	O
essentially	O
Apple	O
's	O
analog	O
of	O
Microsoft	O
's	O
TAPI	B-Library
or	O
Novell	O
's	O
TSAPI	B-Application
.	O
</s>
<s>
To	O
promote	O
the	O
system	O
,	O
in	O
late	O
1994	O
Apple	O
organized	O
the	O
Versit	B-Protocol
alliance	O
along	O
with	O
AT&T	O
,	O
IBM	O
and	O
Siemens	O
to	O
attempt	O
to	O
standardize	O
the	O
commands	O
that	O
the	O
PBX	B-Device
systems	O
responded	O
to	O
.	O
</s>
<s>
Novell	O
announced	O
that	O
they	O
would	O
adapt	O
TSAPI	B-Application
to	O
work	O
on	O
top	O
of	O
the	O
Versit	B-Protocol
standards	O
.	O
</s>
<s>
All	O
of	O
these	O
efforts	O
were	O
hampered	O
by	O
a	O
lack	O
of	O
standardization	O
among	O
PBX	B-Device
vendors	O
,	O
and	O
their	O
lack	O
of	O
real	O
support	O
for	O
GeoPort	B-Device
adapters	O
.	O
</s>
<s>
After	O
two	O
years	O
of	O
effort	O
with	O
little	O
to	O
show	O
for	O
it	O
,	O
Apple	O
eventually	O
gave	O
up	O
on	O
Versit	B-Protocol
,	O
and	O
telephony	O
in	O
general	O
.	O
</s>
<s>
The	O
main	O
problem	O
was	O
that	O
the	O
various	O
PBX	B-Device
companies	O
relied	O
on	O
vendor	O
lock-in	O
to	O
keep	O
their	O
existing	O
customers	O
coming	O
back	O
to	O
them	O
for	O
newer	O
products	O
,	O
so	O
the	O
very	O
concept	O
of	O
a	O
standardized	O
system	O
was	O
seen	O
as	O
a	O
problem	O
rather	O
than	O
a	O
solution	O
.	O
</s>
<s>
Additionally	O
there	O
was	O
no	O
support	O
for	O
high-speed	O
serial	O
on	O
the	O
basic	O
PC	O
,	O
so	O
users	O
would	O
have	O
to	O
buy	O
an	O
add-on	O
card	O
if	O
they	O
were	O
going	O
to	O
use	O
GeoPort	B-Device
,	O
at	O
which	O
point	O
it	O
made	O
just	O
as	O
much	O
sense	O
to	O
buy	O
a	O
custom	O
adaptor	O
on	O
a	O
different	O
card	O
.	O
</s>
<s>
The	O
GeoPort	B-Device
was	O
dropped	O
,	O
along	O
with	O
SCSI	B-Architecture
and	O
ADB	B-Device
,	O
when	O
Apple	O
introduced	O
the	O
iMac	B-Device
in	O
1998	O
;	O
early	O
demonstration	O
models	O
had	O
a	O
software	B-Device
modem	I-Device
based	O
on	O
the	O
GeoPort	B-Device
Telecom	O
Adapter	O
's	O
technology	O
,	O
but	O
this	O
was	O
replaced	O
with	O
a	O
hardware	O
56K	O
modem	B-Application
by	O
the	O
time	O
the	O
iMac	B-Device
shipped	O
.	O
</s>
<s>
The	O
table	O
below	O
shows	O
the	O
name	O
and	O
purpose	O
of	O
the	O
various	O
pins	O
in	O
the	O
GeoPort-enabled	O
serial	B-Protocol
connector	I-Protocol
when	O
used	O
in	O
GeoPort	B-Device
,	O
RS-422	O
(	O
LocalTalk	B-Device
)	O
and	O
RS-232	O
modes	O
.	O
</s>
