The industrial, scientific and medical (ISM) radio bands are radio bands (portions of the radio spectrum) reserved internationally for the use of radio frequency (RF) energy for industrial, scientific and medical purposes other than communications.[1] Examples of applications in these bands include radio-frequency process heating, microwave ovens, and medical diathermy machines. The powerful emissions of these devices can create electromagnetic interference and disrupt radio communication using the same frequency, so these devices were limited to certain bands of frequencies. In general, communications equipment operating in these bands must tolerate any interference generated by ISM equipment, and users have no regulatory protection from ISM device operation.
Despite the intent of the original allocation, in recent years the fastest-growing uses of these bands have been for short-range, low power communications systems. Cordless phones, Bluetooth devices, NFC devices, and wireless computer networks all use the ISM bands.
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The ISM bands are defined by the ITU-R in 5.138, 5.150, and 5.280 of the Radio Regulations. Individual countries' use of the bands designated in these sections may differ due to variations in national radio regulations. Because communication devices using the ISM bands must tolerate any interference from ISM equipment, unlicensed operations are typically permitted to use these bands, since unlicensed operation typically needs to be tolerant of interference from other devices anyway. The ISM bands do have licensed operations; however, due to the high likelihood of harmful interference, licensed use of the bands is typically low. In the United States of America, uses of the ISM bands are governed by Part 18 of the FCC rules, while Part 15 contains the rules for unlicensed communication devices, even those that use the ISM frequencies..
The ISM bands defined by the ITU-R are:
| Frequency range | Center frequency | Availability | |
|---|---|---|---|
| 6.765 MHz | 6.795 MHz | 6.780 MHz | Subject to local acceptance |
| 13.553 MHz | 13.567 MHz | 13.560 MHz | |
| 26.957 MHz | 27.283 MHz | 27.120 MHz | |
| 40.660 MHz | 40.700 MHz | 40.680 MHz | |
| 433.050 MHz | 434.790 MHz | 433.920 MHz | Region 1 only and subject to local acceptance |
| 863.000 MHz | 870.000 MHz | 866.500 MHz | Region 1 only and subject to local acceptance |
| 902.000 MHz | 928.000 MHz | 915.000 MHz | Region 2 only |
| 2.400 GHz | 2.500 GHz | 2.450 GHz | |
| 5.725 GHz | 5.875 GHz | 5.800 GHz | |
| 24.000 GHz | 24.250 GHz | 24.125 GHz | |
| 61.000 GHz | 61.500 GHz | 61.250 GHz | Subject to local acceptance |
| 122.000 GHz | 123.000 GHz | 122.500 GHz | Subject to local acceptance |
| 244.000 GHz | 246.000 GHz | 245.000 GHz | Subject to local acceptance |
Regulatory authorities may allocate other parts of the radio spectrum for unlicensed communication systems, but these are not ISM bands.
Radio frequencies in the ISM bands have been used for communication purposes, although such devices may experience interference from non-communication sources. In the United States, as early as 1958 Class D Citizen's Band was allocated adjacent to an ISM frequency.
In the US, the FCC first made unlicensed spread spectrum available in the ISM bands in rules adopted on May 9, 1985.[2][3]
Many other countries later developed similar regulations, enabling use of this technology. The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took 5 more years. It was part of a broader proposal to allow civil use of spread spectrum technology and was opposed at the time by mainstream equipment manufacturers and many radio system operators.[4]
For many people, the most commonly encountered ISM device is the home microwave oven operating at 2.45 GHz. However, in recent years these bands have also been shared with license-free error-tolerant communications applications such as Wireless Sensor Networks in the 868 MHz, 915 MHz and 2.450 GHz bands, as well as wireless LANs and cordless phones in the 915 MHz, 2.450 GHz, and 5.800 GHz bands. Because unlicensed devices already are required to be tolerant of ISM emissions in these bands, unlicensed low power uses are generally able to operate in these bands without causing problems for ISM users; ISM equipment does not usually include a radio receiver in the ISM band. In the United States, according to 47 CFR Part 15.5, low power communication devices must accept interference from licensed users of that frequency band, and the Part 15 device must not cause interference to licensed users. Note that the 915 MHz band should not be used in countries outside Region 2, except those that specifically allow it, such as Australia and Israel, especially those that use the GSM-900 band for cellphones. The ISM bands are also widely used for Radio-frequency identification (RFID) applications with the most commonly used band being the 13.56 MHz band used by systems compliant with ISO/IEC 14443 including those used by biometric passports and contactless smart cards.
Wireless LAN devices use wavebands as follows:
IEEE 802.15.4, ZigBee and other personal area networks may use the 915 MHz and 2450 MHz ISM bands.
Wireless LANs and cordless phones can also use frequency bands other than the bands shared with ISM, but such uses require approval on a country by country basis. DECT phones use allocated spectrum outside the ISM bands that differs in Europe and North America. Ultra-wideband LANs require more spectrum than the ISM bands can provide, so the relevant standards such as IEEE 802.15.4a are designed to make use of spectrum outside the ISM bands. Despite the fact that these additional bands are outside the official ITU-R ISM bands, because they are used for the same types of low power personal communications, these additional frequency bands are sometimes incorrectly referred to as ISM bands as well.
Also note that several brands of radio control equipment use the 2.4 GHz band range for low power remote control of toys, from gas powered cars to miniature aircraft.
Worldwide Digital Cordless Telecommunications or WDCT is an ISM band technology that uses the 2.4 GHz radio spectrum.