Thank you so much Mr Chris , about this modem it is famous modem wavecom , it support "AT Command " i used it before with plc siemens S7-400 ,it work nice with command AT and script in wincc explorer now i want to use it with plc Allen bradley SLC5/04, in programm created by rslogix 500 the "AT command" is included to send sms to phone i understand the settings of communication in PLC and in modem to communicate between them, also i understand the instruction of sending message in Rslogix AWT but i don't understand the relation between instruction AWT and data file (R6) and data file (ST9 ) and (B3) thank you very much