Tone generator

A positive temperature coefficient (PTC) resistance element for a seat belt monitoring system for an automobile that is adapted to provide timed audible and visual signals when operation of said automobile is initiated without the seat belt being properly buckled;

• said PTC resistance element being characterized by a body of PTC material having an anomaly temperature;
• said body having electrically conductive surface layers on opposite surfaces of said body, one of said conductive surface layers being adapted to be connected to a source of electrical power and said other conductive surface layer defining first, second and third contact areas electrically isolated from each other such that first, second and third PTC resistors are formed by each of said first, second and third contact areas respectively on said other conductive surface layer relative to said one conductive surface layer, said first contact area being adapted to be connected to an electrical ground, said second contact area being adapted to be connected to a lamp for providing said visual signal, and said third contact area being adapted to be connected to provide said audible signal;
• said second contact area being disposed intermediate said first and third contact areas and said first, second and third contact areas being apportioned so that said first PTC resistor is large enough to generate sufficient heat to cause said third PTC resistor to exceed said anomaly temperature within a predetermined time period, and said second PTC resistor is large enough so that its resistance below said anomaly temperature is small enough to permit the lamp to light brightly.