Cellular modems keep Republic on track.

Keeping a million-dollar, 2,000-horsepower piece of equipment operational is a full-time task. For Greenville, S.C.-based Republic Locomotive, cellular technology has made that job a little easier...and a lot more productive.

In 1992, Republic Locomotive introduced the RD20 model diesel electric locomotive. The RD20 is powered by a 2,000-horsepower Detroit Diesel engine, which features a DDEC (Detroit Diesel Electronic Control) microprocessor, the most advanced engine control system available for locomotive appplications. The system reduces maintenance costs, reduces fuel consumption and emissions, improves engine protection and allows for advanced diagnostics.

What makes the control unit unique is that it has access capabilities via a cellular communications link. The cellular system, provided by Advanced Cellular Communications (Charlotte, N.C.), provides remote diagnostic capabilities that allow a technical staff to monitor or diagnose the RD20 Locomotive from locations near or far.

Packaged within the control system is a ZyXel cellular modem, which allows designated programmers access to the locomotivehs processor to monitor the control logic without leaving their desks. The entire cellular diagnostic system is enclosed in an easily accessible unit mounted in the cab of the locomotive.

"Republic Locomotive needed a modem to provide reliable asynchronous data communications at 9.6 kb/s," says John Marker, president of Advanced Cellular Communications. "The speed and reliability is critical for cellular diagnostics."

During the commissioning of a new RD20 locomotive, program logic controls (PLC), such as the sequencing of events, can be fine-tuned with a few commands from the keyboard to accommodate each customer's specific operating procedures. The system can be upgraded by rewriting the software versus replacing the required electrical equipment.

If a mechanical problem occurs, such as load failure, manitenance personnel immediately receive accurate instruction as to what component failed, the location of failure and the proper procedure for repair.

The package also has the flexibility to replace the entire processor memory if memory is lost due to failure of battery back-ups, again from a remot location. Portions of programs can be installed or deleted per customer specification, eliminating a majority of the programmer's down time due to service trips.

Now, if the train breaks down, Republic's technicians can run a diagnostics program from any location. Previously, if a locomotive had a mechanical problem, the technician would fly to the locomotive and run the diganostics program. The problem with this method is that the technician had no way of knowing which parts--if any--would be necessary for the repair until he arrived at the site.

Using cellular communications to determine the problem ahead of time allows the technician to bring need parts with him or perhaps even to determine that repair is not necessary.

As the locomotive moves from one cell to another, ZyCellular uses a fast synchronization immediately after detecting a handoff or power level change, enabling it to hold the connections without losing data. It uses V.42 error control with selective reject, allowing it to maintain high throughput under severe line conditions.