Asterisk Check T1 Status Because Faxes Sent Via Hylafax Fail

If you have a Asterisk system being used for sending and receiving faxes and all of the sudden the faxes all start failing with various error messages the first thing that should be checked is the status of either the analog telephone lines, the T1’s, or the SIP provider you are using as a outbound proxy. Below I describe some of the error messages that may be received via Hylafax in this example as well as how to check the status of the T1’s themselves to make sure that there are no alarms present before you have to get into troubleshooting Hylafax in detail.

Possible Fax Failure Messages Received When Asterisk T1 Fails:

• Failure to train remote modem at 2400 bps or minimum speed; Giving up after 3 attempts to send same page
• RSPREC error/got DCN (sender abort); Giving up after 3 attempts to send same page
• COMREC error in transmit Phase B/got DCN; too many attempts to send
• Unspecified Transmit Phase C error; Giving up after 3 attempts to send same page
• No receiver protocol (T.30 T1 timeout); too many attempts to send
• No response to PPS repeated 3 times.; Giving up after 3 attempts to send same page
• Stop and wait failure (modem on hook); Giving up after 3 attempts to send same page
• Unable to transmit page (NAK at all possible signalling rates); too many attempts to send

When you see numerous errors like the above the first place to start looking into the issue should be on the outbound phone service line to verify that calls can actually be completed. One easy way to do this in Linux for a server running Asterisk and communicating with a T1 line would be to check the circuit status using the dahdi_scan as shown in the below example.

Verify T1 Circuit Status Using dahdi_scan:

As you can see above the card being scanned is a Digium TE410P which will allow up to 4 T1 circuits to be connected. In this example there are circuits plugged into ports one, two, and four. The T1 circuit plugged into port 2 is the route that fax calls take and as you can see above the circuit is showing as “alarms=RED” indicating an issue with the carrier. To resolve this type of issue simply call the T1 service provider and work with them.