Fax with Asterisk 1.8


do i need to modify chan_sip for T.38 fax. i am able to send fax by using spandsp if i use G711, but T.38 fax gives me following error “error initializing channel ‘SIP/channel’ in T.38 mode” and FAXERROR has “T38_NEG_ERROR”. Do i need to get a license? i am using SIP trunk for fax call. please guide


Did you enable T38 fax in sip.conf?



yes i have


but the error is T38_NEG_ERROR, which means i am not getting T.38 synched or provider is not sending on T.38


What is your error correction setting? Default setting is FEC, but you can also set Redundancy. You have to ask your provider which type of redundancy its T.38 implementation supports.


Yes you need to modify and correct all the mistakes and then only you will be able to correct all your mistakes and make the device working.