ISM - Industrial Scientific and Medical.
Term used by the FCC to denote devices which broadcast electromagnetic emissions as a by-product of their operation rather than an intentional consequence compare for example a microwave with ham radio. Also used to refer to the bands of the elecromagnetic spectrum in which these transmissions occur
ISM bands reserved for device operation by the FCC are also being released for use by low-power loss-resistant consumer devices. For example, microwaves typically emit strong rf radiation around 2450mhz, as a consequence they must be heavily shielded to prevent them from causing interfere to other radio systems which operate near that frequency. As consequence of this other consumer devices may also radiate around 2450mhz (henec the 2.4ghz ism band) provided they do not exceede the rf limitations placed on the use of that spectrum. hence the use of 2.4ghz for applications such as cordless phones, bluetooth wireless, and ieee 802.11 which use either Frequency Hopping or Direct Sequence Spread Spectrum schemes to avoid interference caused by other emiting devices such as EFL lights and microwaves.