may for example be a thin sheet of mylar the side of the flexible support member 20 facing the contact conductors 13 is sprayed with a pressure sensitive semiconductor composition layer 22 which may for example be a mixture of any suitable resin e g acrylic resin such as r 20 sold by specialty coatings amp chemicals inc of north hollywood calif and molybdenum disulfide in one embodiment the liquid composition to be sprayed is made by mixing 5 to 10 milliliters resin 40 milliliters resin thinner and 8 5 grams of molybdenum disulfide of course it will be appreciated that numerous other resin and semiconductor material compositions may be used without departing from the spirit of the present invention specifically materials such as sponge iron powder and iron oxide tungsten carbide powder tin oxide powder boron powder or any other semiconductor material may be used although molybdenum disulfide is preferred because of its low noise lubricating characteristics the resultant cover 19 is glued or otherwise mechanically affixed to at least portions of the top of the insulative spacer 18 so that the pressure sensitive resistive layer 22 is in a normally spaced relationship i e the switch is normally open relative to the contact conductors 13 the glued or fixed cover is arranged to permit leakage of air otherwise an air passageway must be provided as referred to in other.