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. Although initially envisioned as providing general information to motorists and travelers, TIS stations have also been developed for supporting emergency public safety communication, and the FCC currently licenses the stations through its Public Safety and Homeland Security Bureau (PSHSB). During a crisis mobile phone networks are often overloaded, and TIS stations can be used to broadcast emergency instructions. Also, during a widespread electrical outage stations equipped with reserve battery or generator power can continue operating, for reception by battery-operated radios. In 2008 the American Association of Information Radio Operators (AAIRO) was formed to represent station operators, and at the time of its formation the group emphasized the ability of TIS stations to broadcast live local updates to affected communities during emergencies. Two forms of transmitting antennas are employed. Most commonly used are standard non-directional vertical antennas. However, an alternate implementation, called "leaky cable", is a form of carrier current transmission, which employs long horizontal conductors, commonly run alongside roadways. Stations using a standard antenna are generally limited to a coverage radius of , with an antenna height of no more than 15 meters (49.2 feet), and a maximum power of 10 watts, although critical evacuation systems, such as those in the Florida Keys and near chemical and nuclear facilities, have been granted waivers to exceed that limit for emergency operations, typically for up to 100 watts. Individual "leaky cable" installations are limited to a length of , although "ribbon systems" consisting of installations sequentially located along a travel route are permitted. Because cable installations are less effective radiators, they are permitted to use up to 50 watts order to achieve a maximum of 2 mV/m at from the cable. In order to limit potential interference to stations operating on adjacent frequencies, TIS transmitters are required to employ a low-pass filter to reduce the transmission of audio frequencies higher than 5 kHz. TIS service history 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