<s>
System	B-Device
Modules	I-Device
(	O
originally	O
known	O
as	O
System	B-Device
Building	I-Device
Blocks	I-Device
;	O
the	O
name	O
was	O
changed	O
around	O
1961	O
)	O
are	O
a	O
DEC	O
modular	O
digital	O
logic	O
family	O
which	O
preceded	O
the	O
later	O
FLIP	B-Device
CHIPs	I-Device
.	O
</s>
<s>
They	O
use	O
transistor	B-Application
inverter	O
circuits	O
,	O
with	O
the	O
transistors	B-Application
operating	O
saturated	O
,	O
to	O
avoid	O
dependence	O
on	O
tight	O
tolerances	O
;	O
they	O
use	O
-3V	O
and	O
0V	O
as	O
logic	O
levels	O
.	O
</s>
<s>
In	O
addition	O
,	O
special	O
modules	O
were	O
available	O
for	O
purposes	O
such	O
as	O
Input/Output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
converters	O
(	O
to	O
standard	O
internal	O
voltages	O
)	O
,	O
bus	O
drivers	O
,	O
lamp	O
and	O
solenoid	O
drivers	O
,	O
A/D	O
conversion	O
,	O
relays	O
,	O
core	O
memory	O
drivers	O
,	O
etc	O
.	O
</s>
