1.   These devices work on the principle that the oscillating frequency of a crystal under an applied voltage changes with crystal Mass.

2.   There is no evidence that these devices actually work.

3.   Although it may be hard to demonstrate the deterrent effect of video cameras, people believe the devices work.

4.   Analog devices work fine for those who just need sounds made louder.

5.   And some pet owners are convinced the device works.

6.   As it happens, the heat-sensing devices will work with increasing efficiency as cold weather tightens its grip in the region.

7.   ATTACK-AIR-SECURITY Look at how the screening devices at airports work and about the new types of security systems now available to detect weapons.

8.   Both devices work especially well with fish, whose delicate flesh seems to invite the smoke to come on in and stay awhile.

9.   Acme devices never work, which leads one to wonder why the Coyote sticks with the company.

10.   But Cardiac Focus still faces many hurdles, including proving its device works well enough to get FDA approval and eligibility for Medicare reimbursement.