What is an ISM (industrial, scientific and medical) device (Part 18)?
Part 18 ISM devices utilize RF energy for non-communicative purposes. They radiate only and do not receive therefore it is highly unlikely that you would ever interfere with an ISM device. See the definition of ISM equipment in 47 CFR 18.107(c).
Shrink wrappers are a fine example of an ISM device. The plastic is heated and semiliquified by a very strong RF field only a few inches away. The sheet of plastic is then lowered onto the rest of the packaging, clings to the product and the cardboard, and resolidifies. Since telecommunications are precluded, and ISM signal will contain not data. The third character of the emission designator for a Part 18 device will always be N (N0N or P0N are most likely). Other ISM devices include; RF lighting systems, paint dryers, jewelry cleaners, industrial microwave ovens, and MRI equipment.
Wireless ethernet cards and cordless phone are Part 15 devices that just happen to be operating on an older more established ISM (Part 18) band. Wireless ethernet cards are Not Part 18 devices.
The prime distinction between Part 18 and Part 15 devices is that Part 18 devices use RF to do something, and Part 15 devices use RF to communicate or send a command.
A recent publicized example titled: "FCC Queries Wireless 'Net Provider About Interference To Hams" Proves that Part 97 has priority over Part 15, and proves that that wireless ethernet gear is indeed Part 15 and not Part 18.
The FCC opened the industrial, scientific and medical (ISM) bands to Part 15 radio use in 1985. Prior to about 1980, the ISM bands were considered unacceptable for radio communication because of harmful interference created by such equipment. But several companies and industry groups petitioned the FCC and showed that by using spread spectrum modulation, low-power radios could coexist with ISM radiators.
The 33 centimeter ham radio band was also born in 1985. The FCC allocated 902 to 928 MHz to ISM (Industrial, Scientific, and Medical) devices. As part of that proceeding, the band was also allocated to the Amateur Radio Service on a secondary basis.
This means hams can use the band as long as they accepted interference from and did not cause interference to this primary user. Part 18 ISM devices utilize RF energy for non-communicative purposes. They radiate only and do not receive therefore it is highly unlikely that you would ever interfere with an ISM device.