Haptic sensations for tactile feedback computer interface devices. For example, an order quantity, a price level, andor a time period between sending any two consecutive orders may be randomized. A bulge and at least one projection are formed on the housing adjacent the front face of the base for engaging with a first face and an opposite second face of a panel, respectively. The cover is made of flat glass cooled by means of a model mould. Due to the low energy pulse, it can be necessary to apply a greater overall amount of energy per treatment area relative to other previous systems, but due to the relatively long period of time between pulses the operation is such that risk of injury is significantly reduced relative to prior systems.