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.
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.
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.
Radio frequencies in the ISM bands have been used for communication purposes, although such devices may experience interference from non-communication sources.
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.
[citation needed] Industrial, scientific and medical (ISM) applications (of radio frequency energy) (short: ISM applications) are – according to article 1.15 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR)[8] – defined as «Operation of equipment or appliances designed to generate and use locally radio frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.» The original ISM specifications envisioned that the bands would be used primarily for noncommunication purposes, such as heating.
In medical settings, shortwave and microwave diathermy machines use radio waves in the ISM bands to apply deep heating to the body for relaxation and healing.
These are sometimes called "non ISM" uses since they do not fall under the originally envisioned "industrial", "scientific", and "medical" application areas.
Some electrodeless lamp designs are ISM devices, which use RF emissions to excite fluorescent tubes.
Also in space applications, a helicon double-layer ion thruster is a prototype spacecraft propulsion engine which uses a 13.56 MHz transmission to break down and heat gas into plasma.
In Europe, the use of the ISM band is covered by Short Range Device regulations issued by European Commission, based on technical recommendations by CEPT and standards by ETSI.
DECT phones use allocated spectrum outside the ISM bands that differs in Europe and North America.