The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF) energy in these bands include RF 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 are limited to certain bands of frequencies. In general, communications equipment operating in ISM bands must tolerate any interference generated by ISM applications, and users have no regulatory protection from ISM device operation in these bands. Despite the intent of the original allocations, in recent years the fastest-growing use of these bands has been for short-range, low-power wireless communications systems, since these bands are often approved for such devices, which can be used without a government license, as would otherwise be required for transmitters; ISM frequencies are often chosen for this purpose as they already must tolerate interference issues. Cordless phones, Bluetooth devices, near-field communication (NFC) devices, garage door openers, baby monitors, and wireless computer networks (Wi-Fi) may all use the ISM frequencies, although these low-power transmitters are not considered to be ISM devices.
Definition The ISM bands are defined by the ITU Radio Regulations (article 5) in footnotes 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 share allocations with unlicensed and licensed operations; however, due to the high likelihood of harmful interference, licensed use of the bands is typically low. In the United States, uses of the ISM bands are governed by Part 18 of the Federal Communications Commission (FCC) rules, while Part 15 contains the rules for unlicensed communication devices, even those that share ISM frequencies. In Europe, the ETSI develops standards for the use of short-range devices, some of which operate in ISM bands. The use of the ISM bands is regulated by the national spectrum regulation authorities that are members of the CEPT.
Frequency allocations The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012). In order to improve harmonisation in spectrum utilisation, the majority of service allocations stipulated in this document were incorporated in national tables of frequency allocations and utilisations which are within the responsibilities of the appropriate national administrations. The allocation might be primary, secondary, exclusive, or shared. Exclusive or shared utilization is within the responsibility of administrations.
Type A (footnote 5.138) = frequency bands are designated for ISM applications. The use of these frequency bands for ISM applications shall be subject to special authorization by the administration concerned, in agreement with other administrations whose radiocommunication services might be affected. In applying this provision, administrations shall have due regard to the latest relevant ITU-R Recommendations. Type B (footnote 5.150) = frequency bands are also designated for ISM applications. Radiocommunication services operating within these bands must accept harmful interference which may be caused by these applications. ITU RR, (Footnote 5.280) = In Germany, Austria, Bosnia and Herzegovina, Croatia, North Macedonia, Liechtenstein, Montenegro, Portugal, Serbia, Slovenia and Switzerland, the band 433.05–434.79 MHz (center frequency 433.92 MHz) is designated for ISM applications. Radio communication services of these countries operating within this band must accept harmful interference which may be caused by these applications.
History
The ISM bands were first established at the International Telecommunications Conference of the ITU in Atlantic City, 1947. The American delegation specifically proposed several bands, including the now commonplace 2.4 GHz band, to accommodate the then nascent process of microwave heating; however, FCC annual reports of that time suggest that much preparation was done ahead of these presentations. The report of the August 9th 1947 meeting of the Allocation of Frequencies committee includes the remark: "The delegate of the United States, referring to his request that the frequency 2450 Mc/s be allocated for I.S.M., indicated that there was in existence in the United States, and working on this frequency a diathermy machine and an electronic cooker, and that the latter might eventually be installed in transatlantic ships and airplanes. There was therefore some point in attempting to reach world agreement on this subject." 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 Citizens Band, a Part 95 service, was allocated to frequencies that are also allocated to ISM. [1] In the U.S., the FCC first made unlicensed spread spectrum available in the ISM bands in rules adopted on May 9, 1985. The FCC action was proposed by Michael Marcus of the FCC staff in 1980 and the subsequent regulatory action took five 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. Many other countries later developed similar regulations, enabling use of this technology.
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