the device is contained and protected by a two - part , hollow , elongated , plastic housing . this housing is comprised of a top half 1 and a bottom half 2 as best depicted in fig2 . fig1 to 3 illustrate how clips 3 hold the top housing half 1 against the bottom housing half 2 and also compress a gasket 4 which serves to seal the union against contaminants such as water . the gasket 4 also clamps the printed circuit board 5 tightly in place against the bottom housing half 2 . the top housing half has two apertures . fig1 and 2 show the window aperture 6 which permits viewing of the digital display 7 which is attached to the printed circuit board 5 below . fig4 shows the flexible lead aperture 8 through which the flexible lead 9 is passed . the flexible lead 9 is a part of one of the layers of the multilayered top panel 10 , which is attached with pressure - sensitive adhesive 11 to the top housing half 1 . the top panel 10 contains membrane switches 12 which are used to control the functions of the device . the portion of the top panel that covers the window aperture 10 is transparent and forms a display window 13 . both the window aperture 6 and the flexible lead aperture 8 are completely covered by the top panel which extends sufficiently beyond them to form a protective seal when the panel is pressed down and adheres itself to the top housing half . fig2 and 3 illustrate how the device is attached to a ski 14 . two thin plastic strips 15 have pressure - sensitive adhesive on one side and a dense pattern of bulb - headed stems , which exetend on axes perpendicular to the plane of the plastic strip , on the other side . one plastic strip is adhered to the top face and rear end of a ski while the other plastic strip is adhered to the bottom side of the bottom housing half 2 . when the device is pressed down upon the ski such that the plastic strip on the bottom of the divice is over the plastic strip on the ski , the two plastic strips engage positively with each other forming a secure method of holding the device to the ski that does not cause permanent damage to the ski such as with screw holes . for the purpose of explanation , this fastening system may be thought of as a kind of plastic velcro ( velcro is a registered trademark ). means are provided to attach to the device a restraint , such as a strap or cord , which may also be attached to the ski , such as to the binding of the ski . this restraint ring 16 is an integral part of the bottom housing half 2 . in the event of an accident whereby the device could become dislodged from the primary fastening system comprised of the two plastic strips , the device could still remain attached to the ski by virtue of said restraint which would prevent the device from being flung off to either strike someone or become lost . the restraint should not attach the device directly to the skier as this could result in injury to the skier in the event of such an accident . fig5 illustrates the toothed wheel 17 tightly attached to the stainless steel shaft 18 and to the magnets 19 . the shaft , hence the wheel , is free to rotate in the recesses of the bifurcated part of the plastic housing that are formed when the top housing half 1 is attached to the bottom housing half 2 . an economical bearing of sufficient quality is thus formed allowing the wheel to rotate with respect to the device and ski . the hall effect sensor 20 is supported in the top housing half 1 as shown in fig2 . the sensor is placed so that it may detect magnetic field changes induced by the passage of the magnets attached to the wheel . for example , in fig5 let the top magnet be oriented so that its north pole points out of the right hand face of the toothed wheel 17 while the bottom magnet is oriented so that its south pole points out of this same side . a rotation of the wheel will be indicated by the hall effect sensor 20 when the magnetic field is sensed to have changed back to its original polarity . this indication is then sent to the microcomputor 21 via the conductive leads ( not shown ) of the hall effect sensor 20 . fig3 exaggerates the protrusion of the wheel from the plane formed by the bottom of the ski . this is done so that the wheel may be more easily recognized as such . in actuality , the wheel would only extend about one - sixteenth of an inch . the cross - sectional view of the device in fig2 shows the major components of the printed circuit board 5 . they comprise the microcomputer 21 , a battery 22 , and the digital display 7 . other support electronics such as resistors , capacitors and a crystal are not shown in order to simplify the figure .
the device accurately calculates , retains and digitally displays the average speeds of and / or distances traveled by a skier . these functions are performed non - mechanically thereby allowing the ski to perform naturally . the device can be easily installed upon and removed from the ski without the use of tools and can mount upon the ski without causing any permanent damage to the ski .