<s>
SP-1	B-Device
(	O
Stored	B-Device
Program	I-Device
1	I-Device
)	O
was	O
the	O
name	O
of	O
a	O
computerized	O
telephone	O
exchange	O
(	O
a	O
so-called	O
switching	O
office	O
)	O
manufactured	O
by	O
Northern	O
Electric	O
(	O
later	O
Northern	O
Telecom	O
and	O
now	O
Nortel	O
Networks	O
beginning	O
in	O
1972	O
)	O
in	O
Canada	O
.	O
</s>
<s>
As	O
indicated	O
by	O
the	O
name	O
"	O
Stored	O
Program	O
"	O
,	O
the	O
SP-1	B-Device
introduced	O
computer	B-Device
control	I-Device
to	O
the	O
telephone	O
switching	O
market	O
.	O
</s>
<s>
(	O
T	O
's	O
#1ESS	O
preceded	O
the	O
SP-1	B-Device
by	O
several	O
years	O
.	O
)	O
</s>
<s>
With	O
its	O
use	O
of	O
computer	O
hardware	O
and	O
software	O
control	O
,	O
the	O
SP-1	B-Device
marked	O
an	O
evolutionary	O
step	O
in	O
telephony	O
design	O
.	O
</s>
<s>
Like	O
the	O
previous	O
generation	O
of	O
systems	O
,	O
the	O
SP-1	B-Device
was	O
an	O
analog	O
switch	O
that	O
used	O
a	O
special	O
form	O
of	O
mechanical	O
relay	O
(	O
Minibar	O
crossbar	O
switch	O
)	O
to	O
provide	O
the	O
voice	O
connections	O
.	O
</s>
<s>
However	O
the	O
SP1	B-Device
replaced	O
the	O
previous	O
generation	O
's	O
complex	O
relay-based	O
controllers	O
(	O
markers	B-Device
)	O
with	O
a	O
modern	O
Harvard	B-Architecture
architecture	I-Architecture
electronic	O
computer	O
,	O
with	O
separate	O
data	O
and	O
program	O
memories	O
.	O
</s>
<s>
The	O
next	O
generation	O
of	O
systems	O
evolved	O
from	O
the	O
SP1	B-Device
design	O
to	O
replace	O
the	O
analog	O
switch	O
with	O
a	O
digital	O
technology	O
.	O
</s>
<s>
SP-1	B-Device
proved	O
the	O
feasibility	O
of	O
software-controlled	O
systems	O
for	O
telephony	O
.	O
</s>
<s>
It	O
set	O
the	O
stage	O
for	O
the	O
introduction	O
of	O
fully	O
digital	O
systems	O
with	O
the	O
development	O
of	O
the	O
DMS	O
(	O
Digital	B-Protocol
Multiplex	I-Protocol
Systems	I-Protocol
)	O
by	O
Nortel	O
in	O
the	O
1970s	O
.	O
</s>
<s>
(	O
Nortel	O
's	O
SL-1	O
(	O
PBX	O
)	O
was	O
Nortel	O
's	O
first	O
fully	O
digital	O
switching	B-Device
system	I-Device
,	O
and	O
it	O
was	O
introduced	O
in	O
service	O
in	O
1975	O
.	O
)	O
</s>
