<s>
Differential	B-General_Concept
TTL	I-General_Concept
is	O
a	O
type	O
of	O
binary	O
electrical	O
signaling	O
based	O
on	O
the	O
transistor-transistor	B-General_Concept
logic	I-General_Concept
(	O
TTL	B-General_Concept
)	O
concept	O
.	O
</s>
<s>
Standards	O
implementing	O
differential	B-General_Concept
TTL	I-General_Concept
include	O
RS-422	O
.	O
</s>
<s>
Normal	O
TTL	B-General_Concept
signals	O
are	O
single-ended	O
,	O
which	O
means	O
that	O
each	O
signal	O
consists	O
of	O
a	O
voltage	O
on	O
one	O
wire	O
,	O
referenced	O
to	O
a	O
system	O
ground	O
.	O
</s>
<s>
A	O
differential	B-General_Concept
TTL	I-General_Concept
signal	O
consists	O
of	O
two	O
such	O
wires	O
,	O
also	O
referenced	O
to	O
a	O
system	O
ground	O
.	O
</s>
<s>
The	O
principle	O
is	O
similar	O
to	O
that	O
of	O
low-voltage	B-Architecture
differential	I-Architecture
signaling	I-Architecture
(	O
LVDS	B-Architecture
)	O
,	O
but	O
with	O
different	O
voltage	O
levels	O
.	O
</s>
<s>
Differential	B-General_Concept
TTL	I-General_Concept
is	O
used	O
in	O
preference	O
to	O
single-ended	O
TTL	B-General_Concept
for	O
long-distance	O
signaling	O
.	O
</s>
<s>
A	O
second	O
advantage	O
of	O
differential	B-General_Concept
TTL	I-General_Concept
is	O
that	O
the	O
differential	O
pair	O
of	O
wires	O
can	O
form	O
a	O
current	O
loop	O
.	O
</s>
<s>
Differential	B-General_Concept
TTL	I-General_Concept
is	O
the	O
most	O
common	O
type	O
of	O
high-voltage	B-General_Concept
differential	I-General_Concept
signaling	I-General_Concept
(	O
HVDS	B-General_Concept
)	O
.	O
</s>
<s>
Differential	B-General_Concept
TTL	I-General_Concept
signaling	O
was	O
used	O
in	O
the	O
Serial	B-Architecture
Storage	I-Architecture
Architecture	I-Architecture
(	O
SSA	O
)	O
standard	O
devised	O
by	O
IBM	O
,	O
but	O
this	O
is	O
mostly	O
obsolete	O
.	O
</s>
<s>
More	O
efficient	O
signaling	O
techniques	O
such	O
as	O
LVDS	B-Architecture
are	O
now	O
used	O
instead	O
.	O
</s>
