A majority of TIS stations operate on 530 kHz, which is reserved exclusively for use by this service, and on the AM expanded band frequencies of 1610–1700 kHz, which is the least congested portion of the AM broadcast band. On 1610 kHz TIS service stations have a co-priority status with broadcasting stations, while on the remaining standard AM broadcasting frequencies, 540 kHz-1600 kHz and 1620–1700 kHz, TIS stations are considered a secondary service, with priority held by standard broadcasting station assignments.