If there is one thing everyone agrees on, it's that visibility is even more important than speed in the real-time supply chain.

After all, what good is it to run your operations at top speed if you don't know when something has gone off the rails? On the other hand, if you can sense what's going on as events occur, you can take steps now to respond to any hiccups in the supply chain.

"When it comes to managing a supply chain, it's not only about optimization," insists Ken Ruehrdanz, business development manager for Dematic (877-725-7500). "It's also about sustaining operations without interruption. That means using real-time sensor technology to monitor material flow in order to rapidly correct a problem or predict a problem before it happens."

Think of the real-time sensor network as the eyes and ears of the supply chain. It can tell you what's going on. More importantly, it can tell you what is not happening that should be happening. "The sooner you can learn what is not going on, the sooner you can take corrective action," says Tom Lehmkuhl, chief technology officer of Forte (513-398-2800).

In some respects, the real-time sensor network is the brains behind the real-time supply chain. "It's not just about getting data," says Ann Breidenbach, director of IBM Sensor and Actuator Solutions (800-426-4968). "Supply chain management today is about analyzing that information so I can improve my processes with it."

Sensor technology is a broad category. It includes mobile computing and wireless radio frequency (RF) communication. It also includes data collection technologies like bar codes, voice, active and passive RFID, programmable logic controllers (PLCs) and GPS-enabled tracking devices. These technologies collect information about the physical characteristics of inventory and assets.

Increasingly, manufacturers and distributors are also employing traditional sensors that collect information about the environment those products operate in. "The primary requirement of the sensor network is identification," says Kevin Ashton, vice president of marketing for ThingMagic (866-833-4069). "But it's also useful to enhance the identity of a product with sensory information."

For instance, a bar code or RFID label attached to a carton can identify the products inside. A sensor attached to that carton can detect whether the temperature inside a trailer was too hot or too cold for the product in the carton, or whether the carton absorbed a shock in transit that could damage the contents.

"A bar code or RFID tag tells operators where something is located," says Rob Conant, vice president of marketing for Dust Networks (510-400-2900). "A sensor tells them how it's functioning in its environment."

Of course bar codes, photo eye sensors and even RFID tags have been in use for decades. But there are three important differences in today's real-time supply chain.

The first difference is that information is being collected at more points in the warehouse and factory and across the supply chain than ever before.

"By having more checks and measures in the supply chain, you can prevent costly mistakes," says Martin Brewer, director of new product developments for Wavelink (888-697-9283). "Put a GPS device on a truck," Brewer adds, "and it can give you a heads up that something isn't going where it's supposed to be going."

The second difference is that more and more applications are being enabled by real-time information. "Now, a supervisor can get a message directly from a WMS (warehouse management system) to handle an exception somewhere in the warehouse, no matter where it is," says Tom Pate, director of sales for LXE (770-447-4224). "A maintenance worker can get his work order delivered wirelessly to a handheld terminal."

Finally, where bar codes, RFID, voice and other data collection technologies traditionally have worked independently of one another, new applications are now emerging that use multiple technologies to create new solutions.

The real-time sensor network is at work in other ways in today's warehouses, distribution centers and factories.

The performance of automated systems can be monitored by a control network. "Our conveyor control system monitors the duty cycle of conveyors to evaluate preventative maintenance schedules," explains Jerry Koch, product director of software and controls for FKI Logistex (877-935-4564). "That allows us to understand whether the duty cycle is higher or lower than we think, and to adjust the maintenance schedule to fit the real world efficiency of the system. That will extend the life-cycle of machines without unwanted surprises."

Koch adds that PC-based control systems can enable activities like monitoring the voltage levels of the system to predict where problems might arise.

Meanwhile, sensors on conveyors can determine if there is no material flow and shut down, saving energy and equipment wear, adds Dematic's Ruehrdanz. And with smart controls, an entire sortation system can use that information to automatically speed up or slow down according to throughput requirements.

Likewise, voice technology is making inroads in operations that previously required an operator to manually scan a bar code. "In operations like receiving and picking, voice not only ensures accuracy, it also improves productivity because a worker doesn't have to stop to scan a bar code," says Jeff Morrow, vice president of marketing for Voxware (609-514-4100).

While applications like system monitoring and voice-directed picking are becoming commonplace, the next generation of real-time data collection solutions is just now emerging.

For example, heat inside a railcar can cause a problem for certain chemicals. "Solutions are now available that use sensors with microcontrollers to sense if the car gets too hot," explains Hal Haygood, president of RFTrax (281-275-5900). "The sensors are tied into cell phone technology that can send a message when that happens and into GPS technology that can let you know where the railcar was located when it occurred. Finally, an escalation engine can follow up to make sure that someone has seen the message and responded according to pre-determined business rules."

Likewise, some experts are predicting the marriage of voice technology and RFID in the distribution center. "What we believe you'll see is voice as the technology that directs pickers on the distribution center floor," says Larry Sweeney, vice president of product management for Vocollect (412-349-2515). "RFID will be the technology to capture and verify data. They work together because both allow for hands-free operation."

In the future, the real-time sensor network will continue to expand, gathering more and more information from more and more points of operation. "Where we're headed is total visibility," says Jerry McNerney, senior director of transportation, distribution and logistics solutions for Symbol Technologies (866-416-8545). "We're not there yet, but it's coming."