Finger glide-and-touch encodes symbols
Glancing Pad has a built in capability to trace and record all fingertip motions in the vicinity of the pad surface, and to detect touches to its surface. Both the off-pad track and the touch are crucial for the Glancing Pad operation. During operation fingers trace an 'endless' loop, and the touch to the pad instructs the underlying program how to locate a symbol-encoding segment within the loop. Actually, the start and end of segments are closely tied to the time of touch (e.g. the segment begins 0.3 sec before and ends 0.05 sec after the touch).
Along with initiating trajectory-processing, touch has another important role to play; it generates tactile information that the hand sensory apparatus sends to the brain. Such haptic feedback is necessary to precisely adjust the motion range, and especially the distances at which the fingers glide above the pad during the glance-encoding motions. Distancing of fingers from the pad has considerable tolerance range, but also has its limits; keeping the fingers too far above makes glancing less efficient, while being too close poses the risk of unintended touching. Good tactile feedback is necessary for the accuracy and confidence of user-performed encoding actions.
Capability to track the position of all fingers when they glide above the pad is critical for Glancing Pad function because each finger position aids in establishing the identity of the finger that came in contact with the pad (the finger to actually encode the symbol).
Tracking the motions of all fingers is necessary for quite another reason. If the data processing program encounters a defective or ambiguous trajectory, the accuracy of such trajectory may be verified and, if needed, corrected by analyzing and comparing traces produced by other fingers (notice that all the fingers of one hand tend to make a simultaneous and broadly similar motion). In situations when recorded signal is noisy or in any other way defective, such redundancy secures accurate decoding.