D
D
X
X
E
E
S
S
e
e
r
r
i
i
e
e
s
s
NEC INFRONTIA ISDN BUSINESS COMMUNICATION SYSTEM
R
R
e
e
g
g
i
i
s
s
t
t
e
e
r
r
i
i
n
n
g
g
a
a
D
D
E
E
C
C
T
T
H
H
a
a
n
n
d
d
s
s
e
e
t
t
o
o
n
n
t
t
h
h
e
e
D
D
X
X
E
E
9
9
6
6
+
+
(
(
I
I
n
n
s
s
t
t
r
r
u
u
c
c
t
t
i
i
o
o
n
n
s
s
f
f
o
o
r
r
t
t
h
h
e
e
C
C
u
u
s
s
t
t
o
o
m
m
e
e
r
r
)
)
DHAH Handset
DHAL Handset