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Phone home-or elsewhere
Embedded systems gain features through wireless technology and phone lines.
Gary Legg, Contributing Editor -- Design News, January 13, 2003
Milpitas, CA — Sometimes you need to be connected, but you don't need the Internet. Credit card transactions are a good example. When you make a credit purchase in a store, you or the cashier swipes your card through a slot to initiate an approval process over a telephone connection. The whole process takes only a few seconds.
Xecom, Inc. (Milpitas, CA), a supplier of telecommunications components, thinks there are other good uses for phone lines, too. Credit-card approvals initiated by vending machines are one example; cashless parking meters are another. Other possibilities include cashless washers and dryers in laundromats, utility meters that phone in their readings, and propane tanks that report their fill levels.
There's only one problem, says Xecom CEO Charles Bellavia. Bringing phone lines to individual vending machines, parking meters, and utility meters isn't usually feasible or cost effective.
Solution? Connecting many devices to a single phone line-wirelessly. New components from Xecom do that, using 900-MHz wireless technology to connect as many as eight points to a single telephone line over distances up to 150 feet. A $39 XE900 Smart Transceiver embedded in each application device, such as a vending machine, communicates wirelessly between the device's microcontroller and a $59 XE924 Base Access Point, which attaches to a phone line. A modem in the XE924 handles the phone-line data communication.
The benefit to the design engineer, says Bellavia, is simplicity. "You give our module serial data, which just goes across a telephone line. The engineer doesn't have to be all caught up with the whole idea of designing the wireless network."
Xecom's 2400-baud data rate is slower than for network or Internet connections, but it's the most commonly used rate for credit-card transactions, which transfer only small amounts of data. Similarly, other applications envisioned by Xecom also have low data requirements. The company does, however, plan a wireless Ethernet product for applications that need more speed. It's also planning upgrades to its telephone product to increase the number of wireless connections from eight to 32 and the wireless range to 1000 feet. Having 32 nodes, Bellavia says, would be good for connecting a laundromat's washers and dryers to a phone line.
The Xecom technology is also well suited to boosting productivity, Bellavia says, as in automatic reading of utility meters. In a cul-de-sac, he notes, meters in many homes could link to a single phone line.
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