Error Code	Display-Text	Description
10	VoIP not available	Busy tone - SIP stack is not running -> no VoIP call possible
20	Invalid IP address	Busy tone - Invalid IP dial info
30	VoIP config error: 0x30	Memory allocation failed
31	VoIP config error: 0x31	No entry for SIP Domain
33	VoIP config error: 0x33	No entry for SIP authentication name
34	VoIP config error: 0x34	No entry for SIP authentication password
300	VoIP status code:: 0x300	This status response is appropriate if the callee can be reached at several different locations and the server cannot or prefers not to proxy the request.
301	VoIP status code:: 0x301	The user can no longer be found at the address in the Request-URI, and the requesting client SHOULD retry at the new address given by the Contact header field. The requestor SHOULD update any local directories, address books, and user location caches with this new value and redirect future requests to the address(es) listed.
302	VoIP status code: 0x302	The requesting client SHOULD retry the request at the new address(es) given by the Contact header field. The Request-URI of the new request uses the value of the Contact header field in the response. The temporary URI may have become out-of-date sooner than the expiration time, and a new temporary URI may be available.
305	VoIP status code: 0x305	The requested resource MUST be accessed through the proxy given by the Contact field. The Contact field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 (Use Proxy) responses MUST only be generated by User Agent Servers (UASs).
380	VoIP status code: 0x380	The call was not successful, but alternative services are possible. The alternative services are described in the message body of the response. Formats for such bodies are not defined here, and may be the subject of future standardization.
400	VoIP status code: 0x400	The request could not be understood due to malformed syntax. The Reason-Phrase SHOULD identify the syntax problem in more detail, for example, "Missing Call-ID header field".
401	VoIP status code: 0x401	The request requires user authentication. This response is issued by User Agent Servers (UASs) and registrars, while 407 (Proxy Authentication Required) is used by proxy servers.
402	VoIP status code: 0x402	Reserved for future use.
403	VoIP status code: 0x403	The server understood the request, but is refusing to fulfill it. Authorization will not help, and the request SHOULD NOT be repeated.
404	VoIP status code: 0x404	The server has definitive information that the user does not exist at the domain specified in the Request-URI. This status is also returned if the domain in the Request-URI does not match any of the domains handled by the recipient of the request.
405	VoIP status code: 0x405	The method specified in the Request-Line is understood, but not allowed for the address identified by the Request-URI. The response MUST include an Allow header field containing a list of valid methods for the indicated address.
406	VoIP status code: 0x406	The resource identified by the request is only capable of generating response entities that have content characteristics not acceptable according to the Accept header field sent in the request.
407	VoIP status code: 0x407	This code is similar to 401 (Unauthorized), but indicates that the client MUST first authenticate itself with the proxy. This status code can be used for applications where access to the communication channel (for example, a telephony gateway) rather than the callee requires authentication.
408	VoIP status code: 0x408	The server could not produce a response within a suitable amount of time, for example, if it could not determine the location of the user in time. The client MAY repeat the request without modifications at any later time.
410	VoIP status code: 0x410	The requested resource is no longer available at the server and no forwarding address is known. This condition is expected to be considered permanent. If the server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 (Not Found) SHOULD be used instead.
413	VoIP status code: 0x413	The server is refusing to process a request because the request entity-body is larger than the server is willing or able to process. The server MAY close the connection to prevent the client from continuing the request.
414	VoIP status code: 0x414	The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret.
415	VoIP status code: 0x415	The server is refusing to service the request because the message body of the request is in a format not supported by the server for the requested method. The server MUST return a list of acceptable formats using the Accept, Accept-Encoding, or Accept-Language header field, depending on the specific problem with the content.
416	VoIP status code: 0x416	The server cannot process the request because the scheme of the URI in the Request-URI is unknown to the server.
420	VoIP status code: 0x420	The server did not understand the protocol extension specified in a Proxy-Require or Require header field. The server MUST include a list of the unsupported extensions in an Unsupported header field in the response.
421	VoIP status code: 0x421	The User Agent Server (UAS) needs a particular extension to process the request, but this extension is not listed in a Supported header field in the request. Responses with this status code MUST contain a Require header field listing the required extensions.
423	VoIP status code: 0x423	The server is rejecting the request because the expiration time of the resource refreshed by the request is too short. This response can be used by a registrar to reject a registration whose Contact header field expiration time was too small.
480	VoIP status code: 0x480	The callee�s end system was contacted successfully but the callee is currently unavailable (for example, is not logged in, logged in but in a state that precludes communication with the callee, or has activated the "do not disturb" feature). The response MAY indicate a better time to call in the Retry-After header field. The user could also be available elsewhere (unbeknownst to this server). The reason phrase SHOULD indicate a more precise cause as to why the callee is unavailable. This value SHOULD be settable by the User Agent (UA). This status is also returned by a redirect or proxy server that recognizes the user identified by the Request-URI, but does not currently have a valid forwarding location for that user.
481	VoIP status code: 0x481	This status indicates that the User Agent Server (UAS) received a request that does not match any existing dialog or transaction.
482	VoIP status code: 0x482	The server has detected a loop. An element MAY check for forwarding loops before forwarding a request.
483	VoIP status code: 0x483	The server received a request that contains a Max-Forwards header field with the value zero.
484	VoIP status code: 0x484	The server received a request with a Request-URI that was incomplete.
485	VoIP status code: 0x485	The Request-URI was ambiguous.
486	VoIP status code: 0x486	The callee�s end system was contacted successfully, but the callee is currently not willing or able to take additional calls at this end system.
487	VoIP status code: 0x487	The request was terminated by a BYE or CANCEL request.
488	VoIP status code: 0x488	The response has the same meaning as 606 (Not Acceptable), but only applies to the specific resource addressed by the Request-URI and the request may succeed elsewhere.
491	VoIP status code: 0x491	The request was received by a User Agent Server (UAS) that had a pending request within the same dialog.
493	VoIP status code: 0x493	The request was received by a User Agent Server (UAS) that contained an encrypted MIME body for which the recipient does not possess or will not provide an appropriate decryption key.
500	VoIP status code: 0x500	The server encountered an unexpected condition that prevented it from fulfilling the request.
501	VoIP status code: 0x501	The server does not support the functionality required to fulfill the request. This is the appropriate response when a User Agent Server (UAS) does not recognize the request method and is not capable of supporting it for any user.
502	VoIP status code: 0x502	The server, while acting as a gateway or proxy, received an invalid response from the downstream server it accessed in attempting to fulfill the request.
503	VoIP status code: 0x503	The server is temporarily unable to process the request due to a temporary overloading or maintenance of the server.
504	VoIP status code: 0x504	The server did not receive a timely response from an external server it accessed in attempting to process the request.
505	VoIP status code: 0x505	The server does not support, or refuses to support, the SIP protocol version that was used in the request. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client, other than with this error message.
513	VoIP status code: 0x515	The server was unable to process the request since the message length exceeded its capabilities.
600	VoIP status code: 0x600	The callee�s end system was contacted successfully but the callee is busy and does not wish to take the call at this time.
603	VoIP status code: 0x603	The callee�s machine was successfully contacted but the user explicitly does not wish to or cannot participate.
604	VoIP status code: 0x604	The server has authoritative information that the user indicated in the Request-URI does not exist anywhere.
606	VoIP status code: 0x606	The user�s agent was contacted successfully but some aspects of the session description such as the requested media, bandwidth, or addressing style were not acceptable.
701	VoIP status code: 0x701	Release Reason: Bye received => disconnect from the remote party
703	VoIP status code: 0x703	Release Reason: sip timeout => LINE disconnect general request timeout
704	VoIP status code: 0x704	Release Reason: sip error => LINE disconnect general internal error
705	VoIP status code: 0x705	Release Reason: out of memory=> "wrong dialing tone" Memory allocation failure
706	VoIP status code: 0x706	can't get a transaction
751	VoIP status code: 0x751	Codec negotiation between caller and callee failed
810	VoIP status code: 0x810	General socket layer error: user of socket not authorized
811	VoIP status code: 0x811	General socket layer error: used socket number is not valid
812	VoIP status code: 0x812	General socket layer error: socket is not connected
813	VoIP status code: 0x813	General socket layer error: memory error on socket layer
814	VoIP status code: 0x814	General socket layer error: socket is not reachable
815	VoIP status code: 0x815	General socket layer error: illegal operation on the socket interface
	IP registration missing	- System start up is not finished - IP network is not working (Ethernet connection not available) - STUN has not determined the type of NAT - SIP stack is running but registration data is missing - SIP registration is invalid