# What do the telephony and error codes mean?

#### The following error codes occur most frequently:

| **401** Access credentials incorrect | The identifier (SIP ID) or the password (SIP password) is incorrect.                                                         |
| ------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------- |
| **404** Phone number unknown         | The phone number does not exist, is not assigned to a line, or is not configured on the recipient's device/telephone system. |
| **486** Busy                         | The remote party reports that the subscriber is busy.                                                                        |
| **487** Hung up                      | The usual signal when the remote party hangs up.                                                                             |

#### Other commonly transmitted codes:

| **100** Call forwarding               | An attempt is being made to connect the call. This code is part of the normal call setup process.                                    |
| ------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ |
| **180** Ring signal                   | The ringing is signaled by the called party's device.                                                                                |
| **183** Connection setup              | The connection is currently being established. A ringing tone or announcement may be heard.                                          |
| **200** OK                            | The call was answered, or the device has registered with the server.                                                                 |
| **301** Permanently forwarded         | A permanent forwarding to another destination is set up.                                                                             |
| **302** Temporarily forwarded         | A temporary call forwarding is set up on the called party's phone.                                                                   |
| **400** Invalid request               | The request contains incorrect parameters. This usually means that you entered data into the wrong field in the phone configuration. |
| **403** Not allowed                   | The subscriber is not authorized to make this call.                                                                                  |
| **407** Proxy authentication required | For outgoing calls, the phone must authenticate itself to the server.                                                                |
| **408** No response (Request Timeout) | Usually occurs when your router or firewall partially or completely does not forward data packets to the phone.                      |
| **480** Temporarily unavailable       | This is received, for example, when the called party has activated DND/Do Not Disturb.                                               |
| **481** Call does not exist           | Occurs rarely, mostly when a status message has not reached its destination.                                                         |
| **482** Loop routing detected         | Loop routing often created by forwarding (A ➔ B ➔ A).                                                                                |
| **488** Call attempt not allowed      | Occurs when the codec used by the device, the encryption, or transmission method (e.g. video) is not supported.                      |
| **500** Server error                  | General server error.                                                                                                                |
| **502** Wrong gateway                 | The gateway (server) in the SIP request is incorrect.                                                                                |
| **503** Service not reachable         | The server's SIP service is temporarily unavailable.                                                                                 |
| **603** Rejected                      | The remote party rejected the call. This can happen manually or automatically.                                                       |


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