<s>
The	O
I.431/430	O
Networking	O
standards	O
are	O
recommendations	O
produced	O
by	O
the	O
ITU	O
.	O
</s>
<s>
They	O
are	O
Layer	B-Application
1	I-Application
specifications	O
for	O
ISDN	B-Protocol
networks	O
,	O
using	O
either	O
an	O
E1	O
or	O
T1	O
circuit	O
.	O
</s>
<s>
The	O
I.431	B-Protocol
standard	O
is	O
known	O
as	O
the	O
'	O
PRI	B-Protocol
Physical	B-Application
Layer	I-Application
 '	O
whereas	O
the	O
I.430	O
is	O
known	O
as	O
the	O
'	O
BRI	B-Protocol
Physical	B-Application
Layer	I-Application
 '	O
.	O
</s>
