Fax¶

Class 1 fax (T.30, MH coding, V.27ter, V.29 and V.17 up to 14400 bit/s), sending PDFs and images and receiving into PDFs, on the SIP line (audio, or T.38 when the far end asks for it) and the line to another phone. A call answered is a fax or a data call by what the caller sends (D-Modem's adaptive answer, AT+FAA=1, on unless the settings turn it off): a fax machine's CNG, a V.8 fax call or T.38 from the far end and the modem says FAX, and the app's fax receiver takes the call by itself; a modem's handshake and it says DATA, then its CONNECT, for the terminal and the bridges. Error correction mode (T.30 Annex A) when the other machine has it: the page in numbered HDLC frames, those a noisy line spoils sent again. Tested against efax, against D-Modem's own T.30 machine (native-test's t30_line, on a clean line and a noisy one), and over SIP with T.38 between the app's engine and dmodemd (sip_fax_line).