Digital mobile communication system designed for nationwide police activities-WIDE system

In 1991, the National Police Agency (NPA) of Japan introduced a new type of digital mobile communication system, called the WIDE system, as a countermeasure against nationwide criminal cases. The WIDE system uses an exclusive radio network for police use. This enables police officers to communicate with each other at any time, even if the public network channels are all in use. The WIDE system has both press-to-talk (simplex) radio and telephone (duplex) functions, and it has such original features as (1) a nationwide communication link and contiguous coverage for broadcasting commands to all the WIDE system terminals in a investigation group (press-to-talk), (2) functioning as a mobile telephone which is connected to both the police and the public telephone network, (3) a function to establish a hotline (non-dialling), and (4) a function to connect a prior terminal call by interrupting an ordinary call when all radio channels are in use. Furthermore, the NPA have introduced new facilities and equipment to improve the service features of the WIDE system. For example, (1) we have developed and introduced a handy WIDE system terminal, which is small and similar to a cellular-phone, for high mobility (for walking policemen), (2) we have set up many radio relay stations, not only on the ground but also under the ground (in blind zones), such as in subway station yards, and (3) we have developed and introduced new data communication equipment and facsimile machines for the WIDE system; using this system, the policemen can transmit and receive image data