<s>
The	O
basic	B-Application
exchange	I-Application
telephone	I-Application
radio	I-Application
service	I-Application
or	O
BETRS	B-Application
is	O
a	O
fixed	O
radio	O
service	O
where	O
a	O
multiplexed	B-Architecture
,	O
digital	O
radio	O
link	O
is	O
used	O
as	O
the	O
last	O
segment	O
of	O
the	O
local	B-Architecture
loop	I-Architecture
to	O
provide	O
wireless	O
telephone	O
service	O
to	O
subscribers	O
in	O
remote	O
areas	O
.	O
</s>
<s>
BETRS	B-Application
technology	O
was	O
developed	O
in	O
the	O
mid-1980s	O
and	O
allows	O
up	O
to	O
four	O
subscribers	O
to	O
use	O
a	O
single	O
radio	O
channel	O
pair	O
,	O
simultaneously	O
,	O
without	O
interfering	O
with	O
one	O
another	O
.	O
</s>
<s>
BETRS	B-Application
may	O
be	O
licensed	O
only	O
to	O
state-certified	O
carriers	O
in	O
the	O
area	O
where	O
the	O
service	O
is	O
provided	O
and	O
is	O
considered	O
a	O
part	O
of	O
the	O
public	O
switched	O
telephone	O
network	O
(	O
PSTN	O
)	O
by	O
state	O
regulators	O
.	O
</s>
