# Informational events

The following events, presented in alphabetical order, provide additional information during a fax session:

Event | Hex | Description
--- | --- | ---
NFXEVN_CANNOT_OPEN_FILE | 0x052007 | The specified file was not located by nfxSendFax, nfxReceiveFax, or nfxAnswerFaxPoll. On transmit, the function continues to the next file in the document queue.
NFXEVN_DOC_BEGIN | 0x052003 | Document transmission or reception started. After you receive this event, you can call nfxGetSessionStatus to verify the negotiated values.
NFXEVN_DOC_END | 0x052004 | Document transmission or reception ended. To retrieve additional status information, call nfxGetSessionStatus or nfxGetDocStatus.
NFXEVN_PAGE_BEGIN | 0x052001 | Page transmission or reception started. To retrieve additional status information, call nfxGetSessionStatus.
NFXEVN_PAGE_END | 0x052002 | Page transmission or reception ended. To retrieve additional status information, call nfxGetSessionStatus.
NFXEVN_POLLED | 0x052005 | The calling fax machine polled NaturalFax.
NFXEVN_PROCEDURE_INTERRUPT | 0x052006 | A procedure interrupt was received from the remote fax machine.
NFXEVN_REMOTE_IDENTIFIED | 0x05200A | The remote terminal information is available. You can check the session status to verify the remote SID and NSF.

## NFXEVN_DOC_END values

The following values can appear in the event value field of the NFXEVN_DOC_END event when NaturalFax successfully receives a fax:

Value | Hex | Description
--- | --- | ---
SUCCESS | 0 | Transmission of the document is complete.
CTA_REASON_RELEASED | 0x1007 | The remote fax machine disconnected the call. Check that events are being handled in a timely fashion. Check your host processor CPU loading. The application will also receive ADIEVN_CALL_DISCONNECTED before NFXEVN_SESSION_DONE.
NFX_T30_EOM | 1 | End of message received from remote fax terminal. More documents to follow.
NFX_T30_EOP | 2 | End of procedure received from remote fax terminal. No more documents will be transmitted.

## NFXEVN_DOC_END and NFXEVN_PAGE_END values

The following values can appear in the event value field of NFXEVN_DOC_END and NFXEVN_PAGE_END events when errors occur when NaturalFax is receiving a fax:

Value | Hex | Description
--- | --- | ---
CTAERR_FILE_WRITE_FAILED | 0x28 | The file is not open or is locked, or the expected amount of data could not be written. Verify that an incorrect handle was not used to close another file.
CTAERR_OUT_OF_MEMORY | 0x6 | Unable to allocate memory for queue, driver or context, for play or record buffers, or for temporary storage. When this error occurs on a DONE event, it may mean that there was insufficient memory on the board.
CTAERR_OUT_OF_RESOURCES | 0x8 | A NaturalFax DSP function could not be started. Check to see that you are using the proper board configuration for your application. Check that you have not exceeded the maximum number of fax operations for your hardware configuration.
CTA_REASON_RELEASED | 0x1007 | The remote fax machine disconnected the call. Check that events are being handled in a timely fashion. Check your host processor CPU loading. The application will also receive ADIEVN_CALL_DISCONNECTED before NFXEVN_SESSION_DONE.
CTA_REASON_STOPPED | 0x1002 | The fax function was stopped by calling nfxStopSession.
NFXERR_CARRIER_LOST | 0x05021D | The received signal fell below the level specified by NFX_RECEIVE_PARMS.threshold, and the fax session was terminated.
NFXERR_CONNECT_FAILED | 0x050201 | The called fax machine was not detected. Check that the number you are dialing is connected to a fax machine.
NFXERR_FAX_SERVICE | 0x050219 | A fatal error occurred in the FAX service.
NFXERR_FXM_SERVICE | 0x05021A | A fatal error occurred in the FXM service.
NFXERR_INTERNAL_ERROR | 0x58000 - 0x5FFFF | An unexpected internal error occurred.
NFXERR_NEGOTIATION_FAILED | 0x050202 | Failed T.30 fax negotiation at the beginning of a session or between documents. When transmitting, this error indicates that training failed (usually due to bad phone line quality) or that the transmitter and receiver capabilities do not match. When receiving, this error indicates that training failed.
NFXERR_NO_PPM | 0x050214 | The receiver has not received a correct post-page message.
NFXERR_PROTOCOL_ERROR | 0x050217 | A T.30 protocol error occurred.
NFXERR_QUEUE_EMPTY | 0x050206 | The specified document queue is empty.
NFXERR_RATE_TOO_LOW | 0x050210 | The receiving or transmitting fax terminal is attempting to receive or transmit at a rate lower than the minrate parameter.
NFXERR_REMOTE_DCN | 0x05021B | The remote terminal has sent an unexpected disconnect (DCN) command frame.
NFXERR_RETRAIN_NEGATIVE | 0x05021E | The page was received with errors, and NaturalFax has requested that the remote transmitter retransmit the last page.
NFXERR_SESSION_FAILED | 0x050209 | The fax session failed due to an unexpected event. May indicate a T.30 timeout or failure to receive a post-page message. Check your host processor CPU and I/O loading.