<s>
In	O
electronics	O
,	O
emitter-coupled	B-General_Concept
logic	I-General_Concept
(	O
ECL	O
)	O
is	O
a	O
high-speed	O
integrated	O
circuit	O
bipolar	O
transistor	O
logic	B-General_Concept
family	I-General_Concept
.	O
</s>
<s>
ECL	O
's	O
major	O
disadvantage	O
is	O
that	O
each	O
gate	O
continuously	O
draws	O
current	O
,	O
which	O
means	O
that	O
it	O
requires	O
(	O
and	O
dissipates	O
)	O
significantly	O
more	O
power	O
than	O
those	O
of	O
other	O
logic	B-General_Concept
families	I-General_Concept
,	O
especially	O
when	O
quiescent	O
.	O
</s>
<s>
The	O
equivalent	O
of	O
emitter-coupled	B-General_Concept
logic	I-General_Concept
made	O
from	O
FETs	O
is	O
called	O
source-coupled	B-General_Concept
logic	I-General_Concept
(	O
SCFL	O
)	O
.	O
</s>
<s>
Originally	O
called	O
current-steering	O
logic	O
,	O
it	O
was	O
used	O
in	O
the	O
Stretch	B-Device
,	O
IBM	B-Device
7090	I-Device
,	O
and	O
IBM	O
7094	O
computers	O
.	O
</s>
<s>
It	O
was	O
also	O
used	O
to	O
make	O
the	O
ASLT	B-Algorithm
circuits	O
in	O
the	O
IBM	O
360/91	O
.	O
</s>
<s>
Older	O
high-end	O
mainframe	O
computers	O
,	O
such	O
as	O
the	O
Enterprise	B-Device
System/9000	I-Device
members	O
of	O
IBM	O
's	O
ESA/390	O
computer	O
family	O
,	O
used	O
ECL	O
,	O
as	O
did	O
the	O
Cray-1	B-Device
;	O
and	O
first-generation	O
Amdahl	O
mainframes	O
.	O
</s>
<s>
(	O
Current	O
IBM	O
mainframes	O
use	O
CMOS	B-Device
.	O
)	O
</s>
<s>
Beginning	O
in	O
1975	O
,	O
Digital	O
Equipment	O
Corporation	O
's	O
highest	O
performance	O
processors	O
were	O
all	O
based	O
on	O
multi-chip	O
ECL	O
CPUs	O
—	O
from	O
the	O
ECL	O
KL10	B-Device
through	O
the	O
ECL	O
VAX	B-Device
8000	I-Device
and	O
finally	O
the	O
VAX	B-Device
9000	I-Device
.	O
</s>
<s>
By	O
1991	O
,	O
the	O
CMOS	B-Device
NVAX	B-Device
was	O
launched	O
which	O
offered	O
comparable	O
performance	O
to	O
the	O
VAX	B-Device
9000	I-Device
despite	O
costing	O
25	O
times	O
less	O
and	O
consuming	O
considerably	O
less	O
power	O
.	O
</s>
<s>
The	O
MIPS	B-Device
R6000	I-Device
computers	O
also	O
used	O
ECL	O
.	O
</s>
<s>
Some	O
type	O
of	O
ECL	O
has	O
always	O
been	O
the	O
fastest	O
logic	B-General_Concept
family	I-General_Concept
.	O
</s>
<s>
Other	O
logic	B-General_Concept
families	I-General_Concept
ground	O
the	O
negative	O
end	O
of	O
the	O
power	O
supply	O
.	O
</s>
<s>
This	O
meant	O
that	O
interoperation	O
between	O
ECL	O
and	O
other	O
logic	B-General_Concept
families	I-General_Concept
,	O
such	O
as	O
the	O
popular	O
TTL	B-General_Concept
family	O
,	O
required	O
additional	O
interface	O
circuits	O
.	O
</s>
<s>
Positive	O
emitter-coupled	B-General_Concept
logic	I-General_Concept
,	O
also	O
called	O
pseudo-ECL	O
,	O
(	O
PECL	O
)	O
is	O
a	O
further	O
development	O
of	O
ECL	O
using	O
a	O
positive	O
5V	O
supply	O
instead	O
of	O
a	O
negative	O
5.2V	O
supply	O
.	O
</s>
<s>
Low-voltage	O
positive	O
emitter-coupled	B-General_Concept
logic	I-General_Concept
(	O
LVPECL	B-General_Concept
)	O
is	O
a	O
power-optimized	O
version	O
of	O
PECL	O
,	O
using	O
a	O
positive	O
3.3V	O
instead	O
of	O
5V	O
supply	O
.	O
</s>
<s>
PECL	O
and	O
LVPECL	B-General_Concept
are	O
differential-signaling	O
systems	O
and	O
are	O
mainly	O
used	O
in	O
high-speed	O
and	O
clock-distribution	O
circuits	O
.	O
</s>
