ISM Band - History

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 2.4GHz 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.

From the proceedings: "The delegate of the United States, referring to his request that the frequency 2450 Mc/s be allotted 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 aeroplanes. 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 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.

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.