The phrase "a device that works" is correct and usable in written English.
It can be used to describe a device that functions properly or effectively.
Example: "After testing several models, we finally found a device that works for our needs."
Alternatives: "a functioning device" or "an operational device".
It's a device that works well when dealing with Los Angeles, a city that is as much invented as constructed.
Researchers have also developed a bionic retina, artificial finger joints and a device that works like an artificial pancreas.
However (to use an old construction), that said is a device that works in the other direction.
"The result is that Replay has been left with a weakening market position and a device that works well but doesn't look as great".
On the other hand, Dr Müller and his team have been unable, as yet, to produce a device that works well outside the cosseted environment of a laboratory.There are several reasons for this.
She is changing her son "just a little bit, darling, not too much," with a device that works like mental Viagra, turning him into a killer though, alas, not of herself.
Most sensible is his idea of forcing private creditors to join in the I.M.F.'s rescue efforts -- a device that worked triumphantly in South Korea in December 1997 and again in Brazil in 1999.
Though he wrote articles of every kind, and books too, his innovation was the investigative column, a device that worked because it was based on hard research rather than mere prejudice and polemic.Not that he was short of prejudice and polemic.
Coincidentally, Dr. Augustine, who no longer has a financial stake in the Bair Hugger, also says he has a safer alternative, a warming device that works more like an electric blanket and does not use forced air.
The system involves store staff wearing a small carrying case equipped with a Bluetooth receipt printer, and a cellular device that works as both a barcode scanner and credit card swiper for transactions.
He has also invented a pocket whistle for cabs; a measuring device that works on the principle of a speedometer (for figuring out distances on road maps); a pocket cigarette roller to be sold for a quarter, and a mirror with shelves and bottles painted on it.
