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