Busy Tone Detection - 3Com MSR 50 Series Configuration Manual

Busy Tone Detection

the calling number is sent to the IP network, and if the function is disabled, the
character "P" or "O" is sent.
In practice, there are various switches and these switches use different signaling
standards. Alike, the call progress tones played on these switches have different
indexes and spectral features. Therefore, it is impossible to identify the busy tones
with a fixed threshold value.
The automatic busy tone detection adopts the intelligent busy tone identification
technology to obtain a set of parameters most reflecting a busy tone feature
through sampling, calculation, and analysis of the input busy tone. You can
configure these parameters on the FXO interface to accomplish the busy tone
detection, thereby resolving the problem that different switches have different
busy tone indexes.
Attention should be paid to the following three points from the detection
perspective:
Busy tone frequency: Most busy tones contain one or two frequencies at
■
present.
Duty ratio: Duration ratio of high/low levels composing a busy tone signal, i.e.,
■
the common called make-break ratio. Different countries or regions have
different specifications about the duty ratio of a busy tone. The national
standard of China is 350 milliseconds/350 milliseconds (10% error allowed).
Detection threshold: threshold used to judge the signal energy. The signal
■
energy higher than the threshold is regarded a high level. Otherwise it is
regarded as a low level.
Figure 651 shows the typical network diagram for automatic busy tone detection.
Telephone A is connected to PBX A that connects to the FXO interface of Router A
via an ordinary telephone line. The connection of the peer end is similar.
Figure 651 Network diagram for automatic busy tone detection
PBX A
FXO
1002
Router A
Telephone A
010-1001
Perform an automatic busy tone detection test as follow:
1 Use Telephone A (010-1001) to dial the number 1002. The FXO interface on
Router A plays a dial tone to PBX A, which then transmits the tone to Telephone A.
Then dial the number 07552001. Telephone B rings. After Telephone B 2 is picked
up, the call is connected.
2 Hang up after hearing the access tone. At this time, PBX B plays a busy tone to
Router A through a line.
FXO Voice Subscriber Line
FXO
WAN
Router B
2247
PBX B
2002
Telephone B
0755-2001