Abstract: A circuit is provided for a tractor/trailer combination to provide a warning in the tractor of an event such as low tire pressure occurring at the trailer utilizing only conventional wiring connections between the tractor and trailer. When low tire pressure occurs, a flasher circuit on the trailer flashes the trailer marker lamps which are normally energized so that the flashing lamps are visible to the operator. The electrical pulses in the marker lamp circuits are sensed by a detector in the tractor to illuminate an indicator lamp in the tractor. A time delay circuit controlling the flasher circuit for providing a self-check function, and for allowing manual flashing of the lamps without triggering the self-check operation.

Abstract: A display indicating events in a motor vehicle includes sensors for signalling the occurrence of each event and a display for sequentially and singly providing at a display window messages corresponding to each sensed event. When an event is sensed, a series of index impulses sequentially indexes the display from a reference condition and simultaneously triggers a counter which registers an output corresponding to each message. A coincidence circuit determines when the counter state is consistent with the sensed event to terminate the index impulse. In the preferred embodiment, the messages are carried by a rotating drum and a switch sensitive to drum position is used to verify that the drum position corresponds to the counter state.