[asterisk-users] line cut

[Rilawich Ango]

Hi all,
  I have a TDM400 with all FXO in it.  I can make outgoing out but the
call will be dropped between 20-30mins suddenly.  Below is the message
shown in the log in the time the call drop.
[Dec 10 23:23:32] DEBUG[3613] dsp.c: ast_dsp_busydetect detected busy,
avgtone: 200, avgsilence 75
[Dec 10 23:23:32] DEBUG[3613] dsp.c: Requesting Hangup because the
busy tone was detected on channel Zap/2-1
  It said that it detect a busy tone and that hangup.  I wonder why
there is a busy tone during the call.  Is it the setting problem?
Anyone can give me some advices?

ango