Hello All I Perform normal audio call test with Freeswitch Server , not sending any dtmf tones or RTT/TTY but still i am getting TTY Message in freeswitch server and i received this event : TDD::RECV_MESSAGE I troubleshoot this issue i check mod_spandsp_dsp.c file and this function is printing an log [DEBUG] mod_spandsp_dsp.c:151 sofia/internal/ 1004@192.168.254.149 got TDD Message [V] and this put_text_msg function called from spandsp_tdd_decode_session function with this line : pvt->tdd_state = v18_init(NULL, FALSE, get_v18_mode(session), V18_AUTOMODING_GLOBAL, put_text_msg, pvt); can anyone give me idea when this v18_init line executing as per my understanding when it receive an Text message at that time it is executing but i dont know how it will detect text message from RTP while it is an just audio call. Please give me suggestions on how this v18_init is detecting text it is related to frequency or any other param and give reference of that file from where v18_init is getting text messages From RTP. Let me know if require any further details, Any help is greatly appreciated. Regards Devang Dhandhalya -- * <https://www.ecosmob.com/> * *Disclaimer* In addition to generic Disclaimer which you have agreed on our website, any views or opinions presented in this email are solely those of the originator and do not necessarily represent those of the Company or its sister concerns. Any liability (in negligence, contract or otherwise) arising from any third party taking any action, or refraining from taking any action on the basis of any of the information contained in this email is hereby excluded. *Confidentiality* This communication (including any attachment/s) is intended only for the use of the addressee(s) and contains information that is PRIVILEGED AND CONFIDENTIAL. Unauthorized reading, dissemination, distribution, or copying of this communication is prohibited. Please inform originator if you have received it in error. *Caution for viruses, malware etc.* This communication, including any attachments, may not be free of viruses, trojans, similar or new contaminants/malware, interceptions or interference, and may not be compatible with your systems. You shall carry out virus/malware scanning on your own before opening any attachment to this e-mail. The sender of this e-mail and Company including its sister concerns shall not be liable for any damage that may incur to you as a result of viruses, incompleteness of this message, a delay in receipt of this message or any other computer problems.