AddTapi.NET 4.0 adds TapiLinePickup methods to pick up a call ringing on another extension. These methods can also be used to pick up a call-waiting call. TapiAddressSupportsPickupCallWaiting property indicates if the telephony hardware supports call-waiting call pickup.

The application can use TapiAddressGetForwardingInfo method to obtain call forwarding information for the address. Forwarding information describes when incoming calls are forwarded and the destination number(s) for call forwarding. New TapiAddressForwardModes property describes forwarding modes supported by the telephony hardware. AddTapi.NET fires ForwardingInfo event when call forwarding information changes.

New version adds TapiCallDeviceSpecificInfo, TapiLineDeviceSpecificInfo and TapiAddressDeviceSpecificInfo properties allowing applications to obtain device-specific information about calls, lines and addresses.

AddTapi.NET 4.0 fires ReInit event when TAPI requires re-initialization. The application can handle this event to shutdown and re-initialize its use of TAPI without application restart. This is especially useful for long-running TAPI applications and services.

Version 4.0 adds Generated event that fires when DTMF digit generation has terminated. The application can use event arguments to find out if the generation was completed successfully or if it was canceled.

When the application opens a line for incoming calls, version 4.0 checks for existing calls on the line and adds them to the TapiLineCalls collection. AddTapi.NET 4.0 also obtains call information and call state for all existing calls automatically.

- Added OutOfOrder, Forwarded, Pickup, Cancelled and BadAddress to the TapiDisconnectMode enumeration to provide more information about the reason for call disconnect.

- Improved compatibility with NeoSpeech and Scansoft Text-to-Speech engines.

- Added TapiLineProviderInfo and TapiLineSwitchInfo properties.

- New MonitorTones flag in TapiAddressCallFeatures indicates if TapiCallWaitForSilence(Int32, Int32) is supported by the telephony hardware.

- Fixed "Cannot find a request that matches reply message" errors that were occuring with some telephony hardware.

- Fixed an error with SIPTAPI telephony service provider.

- Fixed a problem with non-directed TapiCallPark(String) on some systems.