Hi Ray,
To use the IMobilePresenceEvents interface you need to inciude
using Plantronics.Device.Common
using Plantronics.UC.Common
to your source file and add
Plantronics.Device.Common.dll
Plantronics.UC.Common.dll
to your project references.
This interface was invented to support older devices. For newer devices like Voyager Pro, Voyager Legend it is recommended that you use the IDeviceListeners interface and monitor for ATDStateChanged.
Wei Chu