<s>
Digital	B-General_Concept
Subscriber	O
Signalling	O
System	O
No	O
.	O
</s>
<s>
1	O
(	O
DSS1	B-Protocol
)	O
is	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
ISDN	B-Protocol
.	O
</s>
<s>
It	O
is	O
defined	O
by	O
ITU-T	O
I.411	O
(	O
ETS	B-Protocol
300	I-Protocol
102	I-Protocol
)	O
.	O
</s>
<s>
A	O
standard	O
developed	O
by	O
ETSI	O
for	O
Europe	O
is	O
known	O
as	O
Euro-ISDN	B-Protocol
or	O
E-DSS1	O
or	O
simply	O
EDSS1	O
(	O
European	O
DSS1	B-Protocol
)	O
.	O
</s>
<s>
DSS1/EDSS1	O
protocol	O
,	O
in	O
contrast	O
,	O
for	O
example	O
,	O
to	O
the	O
protocol	O
QSIG	O
,	O
designed	O
for	O
use	O
as	O
access	O
to	O
public	O
ISDN	B-Protocol
and	O
asymmetric	O
in	O
the	O
sense	O
that	O
it	O
suggests	O
a	O
link	O
with	O
the	O
network	O
side	O
at	O
one	O
end	O
(	O
digital	B-General_Concept
public	O
telephone	O
exchange	O
)	O
and	O
the	O
user	O
(	O
private	B-Device
branch	I-Device
exchange	I-Device
,	O
PBX	O
)	O
-	O
at	O
the	O
other	O
.	O
</s>
<s>
Since	O
the	O
market	O
for	O
ISDN	B-Protocol
equipment	O
was	O
open	O
,	O
ETSI	O
provided	O
guidance	O
to	O
suppliers	O
of	O
ISDN	B-Protocol
equipment	O
by	O
means	O
of	O
the	O
minimum	O
requirements	O
for	O
inter-connectivity	O
to	O
ISDN	B-Protocol
networks	O
.	O
</s>
<s>
These	O
documents	O
,	O
called	O
NET3	O
for	O
BRI	B-Protocol
and	O
NET5	O
for	O
PRI	B-Protocol
lines	I-Protocol
,	O
described	O
a	O
set	O
of	O
protocol	O
tests	O
terminals	O
should	O
comply	O
to	O
.	O
</s>
<s>
In	O
1989	O
,	O
26	O
network	O
operators	O
from	O
20	O
European	O
countries	O
decided	O
to	O
develop	O
EDSS1	O
as	O
a	O
pan-European	O
standard	O
to	O
replace	O
earlier	O
national	O
protocols	O
(	O
such	O
as	O
FTZ	B-Protocol
1	I-Protocol
TR	I-Protocol
6	I-Protocol
or	O
VN3	O
)	O
.	O
</s>
<s>
EDSS1	O
has	O
been	O
one	O
of	O
the	O
keys	O
to	O
the	O
success	O
of	O
the	O
ISDN	B-Protocol
within	O
European	O
countries	O
(	O
as	O
compared	O
to	O
,	O
for	O
example	O
,	O
the	O
U.S.	O
)	O
.	O
</s>
<s>
Non-European	O
countries	O
using	O
DSS1	B-Protocol
include	O
Australia	O
,	O
Brazil	O
,	O
Iran	O
,	O
India	O
,	O
Israel	O
,	O
New	O
Zealand	O
,	O
Pakistan	O
,	O
Peru	O
,	O
Singapore	O
,	O
South	O
Africa	O
,	O
Sri	O
Lanka	O
,	O
Taiwan	O
,	O
Palestine	O
,	O
Mexico	O
,	O
and	O
the	O
United	O
Arab	O
Emirates	O
.	O
</s>
<s>
The	O
DSS1	B-Protocol
protocol	O
knows	O
four	O
different	O
codesets	O
for	O
information	O
elements	O
.	O
</s>
