Hi all, I encounter a strange problem when trying to fax thro' asterisk. I am able to fax to other fax machine except for a particular fax machine. The moment asterisk dial the fax number, it will hangup. I have checked the HANGUPCAUSE value. It is 42 ,AST_CAUSE_SWITCH_CONGESTION. I notice something different when I dial the number directly with a mobile phone. The moment the fax machine pick up on the far end, it play a strange tone before the usual fax machine noise appear. My guess is that it is this tone that cause asterisk to hangup. Unfortunately, I am not able to provide a make of the fax machine. Anyone have any idea how can I overcome this? Base on what I have read on voip-info.org, it seems like the fax machine is implementing a zapateller like feature on the far end. Thanks in advance. Appreciate any help rendered. Regards, Chin