<s>
Digital	B-General_Concept
Subscriber	O
Signalling	O
System	O
No	O
.	O
</s>
<s>
2	O
(	O
DSS2	B-Protocol
)	O
,	O
as	O
the	O
successor	O
to	O
DSS1	B-Protocol
,	O
is	O
also	O
a	O
digital	B-General_Concept
signalling	O
protocol	O
(	O
D	O
channel	O
protocol	O
)	O
used	O
for	O
the	O
B-ISDN	B-Protocol
.	O
</s>
