Next time you're driving through Orange County in California, try this little trick at an unmanned toll booth: Toss into the basket more than the exact-change amount. Crazy idea? No. Those toll booths outfitted with a new Advanced Toll Payment Machine (ATPM) will figure out how much change you have coming back, and give it to you.

The ATPMs will soon be equipped with the Snap Ultimate I/O, an Ethernet-based controller that can communicate with the lane controllers used at countless toll gates around the country. With that I/O, the ATPM can count your car's axles, determine its vehicle class, calculate the toll, accept cash or credit, dispense change, print receipts, activate toll gates, and allow itself to be remotely monitored over the Internet.

Engineers at Opto 22 (www.opto22.com) designed the Snap Ultimate, which employs up to 16 I/O modules, each with four separate sensor channels, to "talk" to the lane controllers, credit card readers, coin counters, currency readers, toll displays, change dispensers, receipt printers, and numerous other I/O devices. Each module incorporates connectors for wiring to I/O devices, and uses an Ethernet connector atop the processor module to provide the communication link.

A Motorola ColdFire 5407 microcontroller in the processor module serves as the ATPM's brain, and enables TCP/IP-based communication over the Internet with state agencies that monitor each toll booth.