Pleas follow the steps in the following:
Step1. Try with the default settings
Step2. Use the dahdi_monitor to get the busy tone details
1)Log in MyPBX CLI via SSH.
2)Go to directory /persistent/ (cd /persistent).
3)Execute command “dahdi_monitor n –r rx.raw”, n is channel number, for example, if you want to monitor channel 1’s Caller ID signaling, the command is “dahdi_monitor 1 –r rx.raw”.
4)Call in to the PSTN line, wait for 5 seconds, hang up the call, wait for 5 seconds, call in to the same PSTN line again, wait for 5 seconds, then press Ctrl + c to stop the command.
5)Log in via ftp and get the file /persistent/rx.raw.
Step3. Use Cool Edit (a kind of software) to analyze the busy tone detail
Open the rx.raw file as
Sample Rate 8000
Formatted the rx.raw file as 16-bit Intel PCM (LSB, MSB)
Figure Sample Format As
Figure Raw data
Example busy tone signal waveform
Usually, the length of the sound (on time) and the silence (off time) of busy tone are the same. In the example below, one cycle of the busy tone is 250 ms on, 250 ms off.
Figure Busy Tone type 1
In the example below, one cycle busy tone is 210 ms on, 210 ms off, 210 ms on, 210 ms off, 210 ms on, 210 ms off 630 ms on, 210 off.
Figure busy tone type 2
Figure Busy tone type 3
Figure Polarity Reversal signal
Step4. Set up correct settings on PSTN trunk page
Figure Busy detection settings for busy tone type 1
Figure Busy Detection settings for busy tone type 2
Figure Busy Detection settings for busy tone type 3
Figure Busy Detection settings for Polarity Reversal