COM AT+CPAS: Query phone status
AT+CPAS=?
WAIT FOR OK
COM Check state in idle mode
AT+CPAS
WAIT FOR +CPAS: 0
MESSAGE Please call your mobile now (incoming call), so that your mobile is alerting. Press OK when ready...
COM check state while alerting
AT+CPAS
WAIT FOR +CPAS: 3
MESSAGE Now answer the phone, so that call is active... 
COM Check state in active mode
AT+CPAS
WAIT FOR +CPAS: 4
MESSAGE Call will be terminated now...
ATH
WAIT FOR OK
COM try to write a value...
AT+CPAS=1
WAIT FOR ERROR
