2
No signal quality
Weak signal quality
Acceptable signal quality Excellent signal quality
O
B
O
c
Fig. 1
O
O
b
O
O
c
O
O
d
O
O
a
O
O
e
O
O
i
O
O
g
O
O
f
O
O
h
O
1*
O
1(
No signal quality
Weak signal quality
Acceptable signal quality Excellent signal quality