Abstract: A ball/socket switch having a sensing arm affixed to the ball and mounted in relation to a pneumatic tire such that deflation of the tire causes the sensing arm to move the ball in the socket. Preferably, both the ball and the socket are injection molded of glass-filled nylon or ABS plastic. First and second electrical conductors, one affixed to the ball and the other affixed to the socket are normally maintained out of contact by a spring loaded ball detent mechanism. When the deflation of a pneumatic tire causes the ball to move in the socket by an adequate amount, the electrical conductors contact one another. A suitable power source and indicator connected in series with the electrical conductors results in a visual and/or audio indication of conductor contact and, thus, a visual and/or audio indication that the associated pneumatic tire is deflated.