Touch device detection

A contact detection apparatus comprises an interactive surface arranged to detect a contact point; an interface responsive to the detection of a contact point and adapted to determine whether the contact point is a pen event or a touch event and a processor for processing data associated with the contact point on the basis of the determination. A pen event is a contact carried out by an active pen device that is able to communicate with the interface, preferably through a communication back-channel. The interface may include pen detection circuitry to detect a pen and preferably includes circuitry for wirelessly transmitting an interrogation signal responsive to the detection of a contact point and the wireless detection is enabled to detect a wireless signal transmitted by the pen in response to receiving the pen interrogation signal. A touch event is carried out by a finger, thumb or passive pen or stylus. The data associated with the contact point may be marked with a pen event flag or a touch event flag based on the determination of a contact being a pen event or a touch event. The invention is said to improve the functionality of interactive surfaces such as electronic whiteboards.