Patent Issue Delays Warning System

Legal worries over patents are blocking adoption of an official standard for trailer-to-tractor warning communications.

The patent issue frustrates backers of the electronic protocol called PLC4Trucks because they face a looming federal deadline to establish an accepted way to warn the driver of a faulty antilock braking system in a trailer.

PLC4Trucks, a “powerline carrier” method that works over existing wiring between the tractor and trailer, has been unofficially adopted by truck manufacturers as the way of warning a driver of an ABS malfunction. Truck and component makers want the Society of Automotive Engineers’ sanction, but say they will move forward without it if necessary.

The engineers association has said it would not allow the sanction because the technology is patented.

The PLC4Trucks protocol relies on a “multiplexing” device that allows a lone wire to carry multiple coded messages. Thus, a warning signal can be transmitted over the auxiliary circuit of today’s seven-circuit trailer wiring and the seven-pin connector between trailer and tractor. The signal illuminates a warning light on the instrument panel, which should immediately get a driver’s attention, federal regulators insist.

For now, the warning light is at the rear of an ABS-equipped trailer, requiring the driver to look into the sideview mirror to see it.

For the full story, see the June 28 print edition of Transport Topics. Subscribe today.