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Common Fax Errors

The table below lists some of the most common fax error messages along with the likely reason and some troubleshooting steps for resolution.

If these steps to resolve your issue do not help, SignalWire Support can investigate what went wrong with our carrier peers. Please open a support request and include the Fax SID with the error. Per our carrier peers' requirements, these SIDs MUST be from the last 24 hours.

List of common errors​

Connection Failed​

Meaning: There was not receiver on the other end of the call to connect to.

Reason: The destination is not confirmed to receive facsimile transactions.

Troubleshooting Steps:

  • Retry
  • Contact the owner of the destination number to confirm compatibility and connectivity

Document generation error​

Meaning: There was an error while generating the document. This could be due to the file being deleted before sending.

Reason: Internal Service Error.

Troubleshooting Steps:

  • Retry
  • If the issue persists, contact SignalWire support

Failed to train with any of the compatible modems​

Meaning: A remote fax machine was detected, but the sending and receiving modems could not establish communication.

Reason: Connectivity issues.

Troubleshooting Steps:

  • Retry
  • If the issue persists, contact SignalWire support

Fax transmission not established​

Meaning: We could not detect a remote fax machine. This could be due to there being no fax machine on the receiving end or a lack of call clarity.

Reason: Connectivity issues, Carrier issues, T.38 Incompatibility issue.

Troubleshooting Steps:

  • Retry
  • Determine whether remote side was configured

Log entry lost​

Meaning: The call started but the log entry for the call was lost/incomplete. In practice, this is rare and may indicate a system problem.

Reason: Internal Service Error

Troubleshooting Steps:

  • Retry
  • If the issue persists, contact SignalWire support

No response after sending a page​

Meaning: The remote fax machine did not acknowledge that it received a page of the fax. Depending on the remote machine's behavior, it may still have printed the page and any preceding pages.

Reason: Connectivity issues

Troubleshooting Steps:

  • Retry
  • Contact destination to ensure delivery

Received no response to DCS or TCF​

Meaning: The bulk fax service could not successfully determine the remote machine's fax capabilities

Reason: Network or incompatibility issues.

Troubleshooting Steps:

  • Retry
  • Determine whether the remote side was configured for supported fax protocols (T.38/T.30).
  • Ensure the remote side's network is stable.
  • If failures only occur with one number, there's a chance that the remote fax machine is incompatible with our infrastructure.

The call dropped prematurely​

Meaning: The call dropped due to non-fax transmission error. It is likely that the receiver hung up.

Reason: Inbound to SignalWire: The destination is a voice number or not set up to receive faxes. Outbound: The destination is a voice number, or the destination returns ringing for so long that the transmission times out before the handshake can be established.

Troubleshooting Steps: Retry. Note: SignalWire Fax only supports the transmission of PDFs to fax-enabled destinations.

The HDLC carrier did not stop in a timely manner​

Meaning: The fax service initiated a fax transmission with the receiver, but there was synchronization (timing) error that could not be resolved.

Reason: Likely low-quality routes.

Troubleshooting Steps:

  • Retry
  • If network conditions persist, contact SignalWire Support to reach out carrier peer

Timed out waiting for initial communication​

Meaning: A call was established with the receiver, and the bulk fax service attempted to establish a fax session. However, there was no fax response from the receiver. This could be due to there being no fax machine on the receiving end or lack of call clarity.

Reason: No remote fax machine or poor quality routes.

Troubleshooting Steps:

  • Retry
  • If network conditions persist, contact SignalWire Support to reach out to carrier peer

Unexpected DCN while waiting for DCS DIS​

Meaning: "Unexpected DCN (Disconnect) while waiting for DCS (Digital Command Signal) or DIS (Digital Identification Signal)" implies that the fax machine received a disconnect signal unexpectedly during the initial negotiation phase, before the communication parameters were fully agreed upon.

Reason: Network or incompatibility issues.

Troubleshooting Steps:

  • Retry
  • Determine whether the remote side was configured for supported fax protocols (T.38/T.30).
  • Ensure the remote side's network is stable.
  • If failures only occur with one number, there's a chance that the remote fax machine is incompatible with our infrastructure.

Disconnected after permitted retries​

Meaning: The fax service attempted to send the same message multiple times unsuccessfully. This may be due to a call clarity issue.

Reason: Poor network conditions.

Troubleshooting Steps:

  • Retry
  • If network conditions persist, contact SignalWire Support to reach out to carrier peer

Far end cannot receive at the resolution of the image​

Meaning: The remote fax machine does not support receiving faxes sent by our service.

Reason: Quality is too high.

Troubleshooting Steps: Try lowering quality (Resolution is known as "quality" in Programmable Fax).

Received a DCN from remote after sending a page​

Meaning: The remote fax machine responded with a disconnect message after a page was sent successfully. Depending on the remote machine's behavior, it may have still printed the sent page and any preceding pages.

Reason: Poor network conditions.

Troubleshooting Steps:

  • Retry
  • If network conditions persist, contact SignalWire Support to reach out to carrier peer

Unexpected message received​

Meaning: The fax service received a message that it did not expect given the current context.

Reason: Protocol failure.

Troubleshooting Steps: Determine whether the expected number of pages matches the number of successfully transmitted pages. Failure may have been in tearing down the call.

Unexpected DCM after EOM or MPS sequence​

Meaning: The remote fax machine disconnected unexpectedly after receiving a page of a multi-page fax. Depending on the remote machine's behavior, it may have still printed the sent pages and any preceding pages.

Reason: Poor network conditions.

Troubleshooting Steps:

  • Retry
  • If network conditions persist, contact SignalWire Support to reach out to carrier peer

Document loading error​

Meaning: The fax service attempted to generate the message to send but a document was missing.

Reason: Internal Service Error

Troubleshooting Steps:

  • Retry
  • If the issue persists, contact SignalWire support

Invalid ECM response received from receiver​

Meaning: The "Invalid ECM (Error Correction Mode) response received from receiver" error indicates that there's an issue with the error correction process, where the receiving fax machine's response to a request for error correction didn't match expected parameters or was not understood by the sending machine.

Reason: Network or incompatibility issues.

Troubleshooting Steps:

  • Retry
  • If failures only occur with one number, there's a chance that the remote fax machine is incompatible with our infrastructure.