Truthful Mechanisms for One-Parameter Agents

Tire pressure monitors are incorporated in vehicles having pneumatic tires (14) to continuously or periodically measure the air pressure within the tires and to alert the driver should the pressure in one of the tires fall below a predetermined value. A self-contained battery powered rf transmitter unit (10) is affixed within the drop center (22) of each wheel (12) and includes a pressure sensing switch (84). The battery is contained within a housing (20) mounted to the external surface of the wheel adjacent a fill valve (30) through which electrical wires (50) are routed to the transmitter (11). The transmitter employs a programmable unijunction transistor (PUT) timer (56) which generates a pulse every 33 seconds when the air pressure within the tire is above a prescribed value. A receiver (13), located in the passenger compartment of the vehicle, receives the signal(s) from the transmitters and counts the number of signals received over a given time period established by a second internal PUT timer (266). If fewer than a predetermined number of pulses are received during any given time period, a fault condition is indicated and the driver is appropriately warned. The arrangement of the PUT timer circuits allows for independant selection of their respective peak point voltage, peak point current and valley current.