<s>
The	O
IBM	B-Device
1750	I-Device
,	I-Device
2750	I-Device
and	I-Device
3750	I-Device
Switching	I-Device
Systems	I-Device
were	O
telephone	O
exchange	O
systems	O
produced	O
by	O
IBM	O
from	O
the	O
1960s	O
to	O
the	O
1990s	O
.	O
</s>
<s>
IBM	O
engineers	O
in	O
the	O
IBM	O
La	O
Gaude	O
Research	O
Laboratory	O
,	O
north-west	O
of	O
Nice	O
in	O
France	O
,	O
developed	O
an	O
electronic	O
Private	B-Device
Automatic	I-Device
Branch	I-Device
Exchange	I-Device
:	O
the	O
first	O
stored-program-controlled	O
PABX	O
to	O
be	O
marketed	O
and	O
installed	O
in	O
the	O
world	O
.	O
</s>
<s>
Before	O
1969	O
only	O
electromechanical	O
Strowger	B-Device
and	O
Crossbar	O
PABXs	O
were	O
available	O
.	O
</s>
<s>
The	O
family	O
of	O
IBM	B-Device
1750	I-Device
,	I-Device
2750	I-Device
and	I-Device
3750	I-Device
Switching	I-Device
Systems	I-Device
was	O
developed	O
from	O
the	O
IBM	B-Device
1800	I-Device
.	O
</s>
<s>
Each	O
system	O
included	O
twin	O
stored-program	B-Device
controllers	I-Device
(	O
each	O
with	O
32K	O
or	O
64K	O
main	O
storage}	O
;	O
some	O
600,000	O
lines	O
of	O
code	O
;	O
emergency	O
and	O
every-night	O
automatic	O
switchover	O
;	O
twin	O
disks	O
(	O
none	O
for	O
the	O
2750	O
)	O
;	O
and	O
solid-state	O
switching	O
.	O
</s>
<s>
Extension	B-Application
,	O
trunk	O
and	O
tie	O
lines	O
were	O
connected	O
by	O
discrete	O
transistors	B-Application
on	O
plug-in	O
panels	O
.	O
</s>
<s>
The	O
French	O
engineers	O
in	O
IBM	O
La	O
Gaude	O
in	O
the	O
late	O
1960s	O
developed	O
a	O
prototype	O
system	O
based	O
on	O
the	O
IBM	O
1130	O
to	O
handle	O
500	O
telephone	B-Application
extensions	I-Application
and	O
some	O
20	O
trunk	O
lines	O
to	O
the	O
local	O
telephone	O
exchange	O
.	O
</s>
<s>
They	O
then	O
developed	O
the	O
marketable	O
IBM	O
2750	O
Switching	O
System	O
,	O
code	O
named	O
Carnation	O
,	O
with	O
IBM	B-Device
1800	I-Device
computers	I-Device
–	O
two	O
1800s	O
for	O
fail-safe	O
redundancy	O
–	O
each	O
with	O
32K	O
or	O
later	O
64K	O
of	O
magnetic-core	O
memory	O
,	O
and	O
IBM	B-Algorithm
Solid	I-Algorithm
Logic	I-Algorithm
Technology	I-Algorithm
(	O
SLT	O
)	O
,	O
but	O
no	O
disks	O
(	O
disk	O
storage	O
was	O
new	O
and	O
very	O
expensive	O
then	O
)	O
.	O
</s>
<s>
Maximising	O
reliability	O
,	O
each	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
had	O
its	O
own	O
transistorised	B-Application
switching	O
network	O
with	O
crosspoint	O
switching	O
.	O
</s>
<s>
The	O
2750	O
had	O
large	O
40cm-by-30cm	O
plug-in	O
extension	B-Application
packs	O
each	O
handling	O
only	O
four	O
telephone	B-Application
extensions	I-Application
with	O
standard	O
PTT	O
50-volt	O
telephones	O
.	O
</s>
<s>
The	O
Assembler-language	B-Language
program	O
was	O
loaded	O
using	O
punched	O
paper	O
tape	O
,	O
needing	O
some	O
90	O
minutes	O
for	O
each	O
of	O
the	O
two	O
CPUs	B-General_Concept
.	O
</s>
<s>
An	O
attached	O
IBM	O
Selectric	O
typewriter	O
let	O
customers	O
change	O
system	O
facilities	O
such	O
as	O
the	O
extension	B-Application
numbers	O
of	O
telephones	O
of	O
repositioned	O
staff	O
.	O
</s>
<s>
The	O
2750	O
was	O
very	O
quiet	O
as	O
it	O
was	O
transistorised	B-Application
with	O
no	O
moving	O
parts	O
other	O
than	O
the	O
cooling	O
fans	O
in	O
the	O
cabinets	O
,	O
compared	O
with	O
the	O
noisy	O
,	O
electro-mechanical	O
Strowger	B-Device
PABX	O
systems	O
then	O
everywhere	O
across	O
Europe	O
.	O
</s>
<s>
Early-1970s	O
computers	O
had	O
hardly	O
any	O
typewriter-like	O
terminals	O
and	O
certainly	O
no	O
screens	O
–	O
the	O
IBM	O
Switching	O
Systems	O
introduced	O
the	O
novelty	O
of	O
simple	O
digital-data	O
capture	O
from	O
every	O
touch-tone	O
telephone	B-Application
extension	I-Application
.	O
</s>
<s>
Non-dialled	O
connection	O
(	O
an	O
off-hook	O
extension	B-Application
automatically	O
dials	O
an	O
extension	B-Application
)	O
.	O
</s>
<s>
These	O
multiple	O
interconnected	O
systems	O
had	O
central	O
operating	O
and	O
control	O
functions	O
,	O
tie-line	O
busy	O
back-up	O
or	O
rerouting	O
via	O
the	O
public	O
network	O
,	O
traffic	O
saturation	O
control	O
,	O
tie-line	O
access	O
restriction	O
,	O
network	O
numbering	O
up	O
to	O
7	O
digits	O
,	O
remote	O
paging	O
,	O
camping-on	O
a	O
remote	O
extension	B-Application
,	O
and	O
adding	O
a	O
third	O
party	O
remotely	O
.	O
</s>
<s>
In	O
1987	O
IBM	O
started	O
to	O
market	O
the	O
ROLM-derived	O
IBM	B-Device
8750	I-Device
Business	I-Device
Communications	I-Device
System	I-Device
in	O
Austria	O
,	O
Belgium	O
,	O
France	O
,	O
Germany	O
,	O
Italy	O
,	O
Luxemburg	O
,	O
and	O
the	O
UK	O
.	O
</s>
<s>
The	O
8750	O
had	O
from	O
91	O
to	O
3000	O
telephone	B-Application
extensions	I-Application
;	O
up	O
to	O
1000	O
simultaneous	O
conversations	O
;	O
a	O
computer	O
based	O
on	O
a	O
Motorola	B-Device
68020	I-Device
;	O
up	O
to	O
16	O
IBM	O
8755	O
Operator	O
Consoles	O
;	O
a	O
30MB	O
fixed	O
disk	O
;	O
main/satellite	O
working	O
with	O
3750s	O
and	O
1750s	O
;	O
digital	O
trunks	O
in	O
Belgium	O
,	O
Italy	O
and	O
the	O
UK	O
;	O
and	O
used	O
ISDN	B-Protocol
and	O
Systems	B-Architecture
Network	I-Architecture
Architecture	I-Architecture
(	O
SNA	O
)	O
networks	O
.	O
</s>
