# ACU primitives summary

NMS supports the generic ISDN protocol, but no longer supports the Omnitel stack. The following table summarizes the supported ACU message primitives and indicates which primitives are deprecated:

Message type | Description
--- | ---
ACU_ALERT_IN | Indicates an alert.
ACU_ALERT_RQ | Sends an alert message.
ACU_CALLID_IN | Delivers a callid or reports a failure to an application.
ACU_CALL_PROC_IN | Indicates incoming call proceeding information (receipt of SETUP ACK, CALL PROCEEDING messages).
ACU_CALL_PROC_RQ | Requests events indicating the progress of a call.
ACU_CLEAR_CO | Confirms that the call has been released.
ACU_CLEAR_IN | Indicates the release of a call.
ACU_CLEAR_RQ | Requests release of a call.
ACU_CLEAR_RS | Indicates a response to a release indication.
ACU_CONN_CO | Indicates a call connection confirmation.
ACU_CONN_IN | Signals an incoming call.
ACU_CONN_RQ | Requests establishment of an outgoing call.
ACU_CONN_RS | Answers an incoming call.
ACU_D_CHANNEL_STATUS_IN | Indicates status of D channel.
ACU_D_CHANNEL_STATUS_RQ | Requests status of the D channel.
ACU_DIGIT_IN | Receives called number digits in overlap receiving mode.
ACU_DIGIT_RQ | Requests called number digits in overlap receiving mode.
ACU_ERR_IN | Indicates an error.
ACU_FACILITY_IN | Indicates a specific facility.
ACU_FACILITY_RQ | Requests a specific facility.
ACU_NOTIFY_IN | Indicates that a NOTIFY message was received.
ACU_NOTIFY_RQ | Requests that a NOTIFY message be sent.
ACU_PROGRESS_IN | Indicates outgoing call progress information (receipt of PROGRESS message).
ACU_PROGRESS_RQ | Indicates progress request.
ACU_RESTART_IN | Indicates that a RESTART ACKNOWLEDGE message has been received.
ACU_SERVICE_CO | Indicates that a SERVICE ACKNOWLEDGE message has been received.
ACU_SERVICE_IN | Indicates that a SERVICE message has been received.
ACU_SERVICE_RQ | Requests that a SERVICE message be sent.
ACU_SETUP_ACK_IN | Acknowledges incoming call proceeding information.
ACU_SETUP_REPORT_IN | Signals that the ACU rejected or ignored an incoming call because it was not compatible (address or service filtering). The application must not answer this incoming call indication. This message is only for information purposes.
ACU_TRANSFER_CO | Indicates whether or not the attempted transfer was successful.
ACU_TRANSFER_RQ | Requests the transfer of two calls.