The capacitive sensing system

The touchpad has a voltage source applied to each corner.  This creates a uniform voltage field -monitored by a microprocessor- across the surface of the pad. Touching the pad disturbs the uniform field and induces a current to flow.  By analysing these induced current flows, the position of the finger (or pointer) on the pad can be calculated.

The projected capacitive system

OCC was asked to modify existing touchpad technology to allow glass of a thickness of up to 5cm to be placed in front of the touchpad. This enabled the creation of weatherproof, vandalproof systems. The input device can now be placed inside a shop and entries made from outside. This feature has been widely used in the computer systems of tourist information kiosks.