public static extern ACSFunctionRet_t attSendDTMFToneExt(ref PrivateData_t privateData, ref ConnectionID_t sender, ref ATTConnIDList_t receivers, [MarshalAs(UnmanagedType.LPStr)] string tones, short toneDuration, short pauseDuration);
public static extern Acs.RetCode_t attSendDTMFToneExt( [In, Out] Acs.PrivateData_t privateData, Csta.ConnectionID_t sender, ref ATTConnIDList_t receivers, string tones, short toneDuration, short pauseDuration);