...
typedef
enum CALL_STATE
    {   CS_IDLE = 0,
        CS_INPROGRESS   = ( CS_IDLE + 1 ) ,
        CS_CONNECTED    = ( CS_INPROGRESS + 1 ) ,
        CS_DISCONNECTED = ( CS_CONNECTED + 1 ) ,
        CS_OFFERING     = ( CS_DISCONNECTED + 1 ) ,
        CS_HOLD         = ( CS_OFFERING + 1 ) ,
        CS_QUEUED       = ( CS_HOLD + 1 ) ,
        CS_LASTITEM     = CS_QUEUED
    } 	CALL_STATE;
...