The line cannot be opened due to a persistent condition, such as that of a serial port being exclusively opened by another process.

The specified device identifier or line device identifier is invalid or out of range.

The bearer mode is invalid, the bearer mode is not available, or the call's bearer mode cannot be changed to the specified bearer mode.

All call appearances on the specified address are currently in use.

The maximum number of outstanding call completions has been exceeded.

The maximum number of parties for a conference has been reached, or the requested number of parties cannot be satisfied.

The dialable address contains dialing control characters that are not processed by the service provider.

The dialable address contains dialing control characters that are not processed by the service provider.

The dialable address contains dialing control characters that are not processed by the service provider.

The dialable address contains dialing control characters that are not processed by the service provider.

The application requested a TAPI version or version range that is either incompatible with, or cannot be supported by, the Telephony API implementation and the corresponding service provider.

The application requested an extension version range that is either invalid or cannot be supported by the corresponding service provider.

The Telephon.ini file cannot be read or understood properly by TAPI because of internal inconsistencies or formatting problems. For example, the [Locations], [Cards], or [Countries] section of the Telephon.ini file may be corrupted or inconsistent.

The line device is in use and cannot currently be configured, allow a party to be added, allow a call to be answered, allow a call to be placed, or allow a call to be transferred.

A specified address is either invalid or not allowed. If invalid, the address contains invalid characters or digits, or the destination address contains dialing control characters, W, @, $, or ?, that are not supported by the service provider. If the address is not allowed, the specified address is either not assigned to the specified line or is not valid for address redirection.

The specified address identifier is either invalid or out of range.

The specified address mode is invalid.

The specified address state contains one or more bits that are not LINEADDRESSSTATE.

The application handle or the application registration handle is invalid.

The specified application name is invalid. The application name should not contain any non-displayable characters, and should be zero-terminated.

The specified bearer mode is invalid.

The specified completion is invalid.

The specified call handle is not valid.

The specified call parameters are invalid.

The specified call privilege parameter is invalid.

The specified select parameter is invalid.

The current state of a call is not a valid state for the requested operation.

The specified call state list is invalid.

The permanent card identifier could not be found in any entry in the [Cards] section in the registry.

The completion identifier is invalid.

The specified call handle for the conference call is invalid or is not a handle for a conference call.

The specified consultation call handle is invalid.

The specified country/region code is invalid.

The line device has no associated device for the given device class, or the specified line does not support the indicated device class.

The line device handle is invalid.

The dialing parameters are invalid.

The specified digit list is invalid.

The specified digit mode is invalid.

The specified termination digits are not valid.

The service provider extension version number is invalid.

The specified group identifier is invalid.

The specified call, device, line device, or line handle is invalid.

The device configuration may not be changed in the current line state.

The permanent location identifier could not be found in any entry in the [Locations] section in the registry.

The specified media list is invalid.

The list of media types (modes) to be monitored contains invalid information, the specified media type parameter is invalid, or the service provider does not support the specified media type.

The number given in MessageID is outside the range specified by the NumCompletionMessages member.

A parameter or structure that a parameter points to contains invalid information, a country/region code is invalid, or the specified forward list parameter contains invalid information.

The park identifier is invalid.

The specified park mode is invalid.

One or more of the specified pointer parameters are invalid, or a required pointer to an output parameter is NULL.

An invalid flag or combination of flags was set for the Privileges parameter.

The specified rate is invalid.

The RequestMode indicator is invalid.

The specified terminal identifier is invalid.

The specified terminal modes parameter is invalid.

Timeouts are not supported or a value falls outside the valid range.

The specified custom tone does not represent a valid tone or is made up of too many frequencies or the specified tone structure does not describe a valid tone.

The specified tone list is invalid.

The specified tone mode parameter is invalid.

The specified transfer mode parameter is invalid.

No lines were found that match the requirements specified in the CallParams parameter.

The specified call is not a conference call handle or a participant call.

The specified device identifier, which was previously valid, is no longer accepted because the associated device has been removed from the system since TAPI was last initialized. Alternately, the line device has no associated device for the given device class.

Either Tapiaddr.dll could not be located or the telephone service provider for the specified device found that one of its components is missing or corrupt in a way that was not detected at initialization time. The user should be advised to use the Telephony Control Panel to correct the problem.

Insufficient memory to perform the operation, or unable to lock memory.

There currently is no request pending of the indicated mode, or the application is no longer the highest-priority application for the specified request mode.

The application does not have owner privilege to the specified call.

The application is not registered as a request recipient for the indicated request mode.

The operation failed for an unspecified or unknown reason.

The operation is not available, such as for the given device or specified line.

The service provider currently does not have enough bandwidth available for the specified rate.

Insufficient resources to complete the operation. For example, a line cannot be opened due to a dynamic resource overcommitment.

More requests are pending than the device can handle.

The TotalSize member of a structure does not specify enough memory to contain the fixed portion of the specified structure.

A target for the call handoff was not found.

The application invoking this operation is the target of the indirect handoff.

The operation was invoked before TAPI was initialized.

The string containing user-user information is too long.

TAPI reinitialization has been requested, all applications should shut down its usage of TAPI.

The specified address is blocked from being dialed on the specified call.

The billing mode of the call was rejected

The requested Feature parameter is invalid.

A telephony service provider that does not support multiple instances is listed more than once in the [Providers] section in the registry. The application should advise the user to use the Telephony Control Panel to remove the duplicated driver.

The specified agent identifier is invalid.

The application referenced an agent group that is not valid.

The application used an invalid password.

The application referenced an agent state that is not valid.

The specified agent activity is not valid

Use of the dial modifier (:) is not supported.

The user cancelled the call.

The application referenced an address type that is not valid.

The agent session state is invalid.

The call has been disconnected.

The TAPI service is not running.