Abstract: A system for monitoring tire pressure preferably at each and every tire to provide an indication of low, unsafe pressure to the operator of the vehicle. The system can be used in pleasure vehicles or commercial trucks and basically comprises a sensor unit mounted to the tire rim including an actuating switch and coupling coil, and a detector unit physically unattached to the sensor unit and also including a coupling coil and associated detecting and indicating circuitry. The sensor unit rotates with the tire and rim while the detector unit, which is preferably mounted to the brake shoe, is stationary enabling inductive coupling between sensor and detector units once each revolution of the wheel of the vehicle. The sensor unit is secured to the inner surface of the rim and is compressable to operate the actuating switch. The detector unit may be powered directly from the vehicle storage battery or may tie into an existing diagnosis system of the vehicle.

Abstract: A display panel or console is mounted in the driving compartment of the vehicle in a position to be observed by the driver and provides status information regarding, for example, the operability of the headlights or taillights, and position information concerned primarily with the position of the trailer relative to the cab and whether there is a "jacknife" condition. The system may also check the status of truck tire pressure and brake drum temperature to determine if the pressure is too low or the temperature too high. The lights, for example, are checked by monitoring the continuity to the filament. The existing lines to the lamp are pulsed with a filtered square wave signal and a resistance sensor determines continuity; a lack of continuity causing illumination of the associated status lamp of the display panel. In another arrangement a memory circuit is associated with each indicator circuit so that a fault condition is stored and remains stored even if corrected.

Abstract: Power lines within a building or other user location are connected through a fuse and a filter to an external power grid that supplies power at the usual 50 Hz or 60 Hz. Communications apparatus such as a central computer and a number of typewriters is connected to the power lines within the building at at least two locations and transmits communications signals over the power lines. The communications signals have a frequency different from the frequency of the electrical power supplied by the external power grid and preferably in the audio range. The filter is tuned to pass the electrical power but substantially to block passage of the communications signals. Two important advantages are that the power lines within the building double as communications lines and that the building presents a purely resistive load to the external power grid, so that the grid has an improved power factor.