Thank You for Your time and answer, Jasper: > chat -E -s -V -f $modem_chat_script <$modem_device >$modem_device Excuse me for my previous messages - I did not see this Your message. So, that's what I did: $ /usr/sbin/chat -E -s -V -f /tmp/qq </dev/ttyUSB0>/dev/ttyUSB0 Failed in /tmp/qq I have: atd*#06# Do You know what can be the reason?