The "upsell" is a big feature of the product, says Terry Bader, the vice president of marketing and strategy for eTab International, which makes one of the devices being tested by Applebee's. "We can prompt consumers at the table with a message, 'Hey, how about another round of drinks?'" Bader says. At Chevys, which is testing the Ziosk in 12 of its 60 U.S. locations, the device shows dessert photos around 20 minutes after a waiter comes to the table.

Dessert orders are about 30% higher than before restaurants used the Ziosk, says Mike Bova, the senior vice president of operations for ERJ Dining, a Chili's franchise with 122 restaurants that have used the Ziosk since 2010. Brinker International, which owns the Chili's brand, says all of the Ziosks in use are operated by franchise partners.

Rather than a table device, T.G.I. Friday's recently launched a free cellphone application for diners. It shows users the menu at their local Friday's, offers discounts and can be used to pay the bill. Using technology from Tabbedout, diners enter their credit-card information into the app, which links with the restaurant's computer system when on-site. The app doesn't take food orders because "that is a human interaction that at this point we don't want to lose," says Trey Hall, senior vice president and chief marketing officer for the company.

Pay-at-the-table systems make low tippers more generous, restaurants say. The systems are designed to suggest a tip amount, say 20%, letting users adjust up or down.

Tips are above average when people use T.G.I. Friday's app to pay, Hall says. The app suggests an 18% tip. More than 90% of restaurant diners choose the predetermined tip on Viableware's device, a pay-at-the-table device that looks like a traditional black bill holder, the company says.

P.F. Chang's China Bistro plans to test the device. Like tabletop machines, it lets users divide up the bill, add a tip, swipe a credit card and email themselves a receipt. It doesn't offer entertainment. "The dining experience is the entertainment experience, and we don't want to clutter that," says Steve Stoddard, the president of Viableware.

Lights on some machines signal to waiters if a patron is paying or needs help.

At Chevys in New York's Times Square, after two weeks of using a Ziosk, waitress Teri Hurst is careful to turn the machine away from children while explaining the gaming options to parents, just as she would while explaining dessert options. "I call them apps, not games," says the 37-year-old. Playing games costs 99 cents at Chevys. Enough people play that the games have become a profit source for the restaurant, general manager Mike Alasaad says.

Earlier this year, Texas Roadhouse, the second-largest steakhouse chain in the U.S. after Outback Steakhouse, tested the Ziosk to see "if we could cut some time off the table turn," spokesman Travis Doster says, using the industry term for time spent at a table. Waiters found that recharging the machines was bothersome and that the devices hogged space on tables already "busy with peanut buckets and bread baskets and all," he says. Table turn decreased slightly, but the company doesn't plan to offer the device, he says.

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