In our system we have a 2821 router with IOS version c2800nm-advipservicesk9-mz.124-15.T10.bin. There is an FXo card on it and an analog line is connected to that. I can receive faxes successfully on this system by using T.37 but there are some problems about offramp. I can send fax to our T.38 system or other T.37 systems but the problem is about sending faxes to fax machines.
There is a setting on fax machines called rings to answer which configures the ring times before the machine sends a fax tone ( fax machines that have both fax and phone). On most machines this setting is 5. The default time in our country before the service provider disconnects the call if the called party does not answer the call is 60 sec's. But during offramp process, I realized that this time is about 35 sec's so I try to send a fax to the fax machine, the machine rings for 5 times but before one or two secs the fax machine send a fax tone, our router drops the connection.
I made some tests on the line to understand if the line has some problems, I connected an analog phone to the line and called somewhere. It ringed for 10 times. Also, to understand if problem is about FXO, I have made the same test with softphone. In that case it also ringed for 60 secs and then disconnected.
So I am sure that there is some problem about T.37 system and analog line. I am trying to fing a way to increase the time that the router waits for before droping the connection with the remote fax machine.
I would be very appreciated if you can help me..