The TIS service was first authorized by the FCC in 1977 following two years of study. At this time the standard AM broadcast band ran from 540 kHz to 1600 kHz, and the new TIS service was initially assigned exclusive use of the two adjoining frequencies of 530 kHz and 1610 kHz. However, on June 8, 1988 an International Telecommunication Union conference held at Rio de Janeiro, Brazil adopted provisions, effective July 1, 1990, to extend the upper end of the AM broadcast band in the Americas, by adding ten frequencies which spanned from 1610 kHz to 1700 kHz.