Conventional communication for train operation mainly consisted of wire telephony "direct telephones" between the dispatcher and each station, and "wayside telephones" placed along railway tracks for train drivers.
Train radio systems comprising radio telephones and train safety radio devices, were applied to about 7,000 km of existing lines in 1986, aiming to establish an efficient train operation system, ensure safe and steady transport, and improve passenger services. Table 5 shows train radio functions in JNR.
At the time, there was a strong requirement for a reduction in the number of employees engaged in train operation, mainly to realize one-man freight train operation, thereby improving railway management. The train safety radio has a function that allows the driver to push a train safety button immediately when he locates an accident in the area the train is traveling through, to transmit a train radio wave and warn other trains within 1 km or so from the train. Following this, using the radio telephone, he can contact the dispatcher of the train dispatch center directly. In the conventional system to date, the driver had to run to the nearest wayside telephone. The radio telephone is also used for passenger services, for instance, to acquire accurate information from a dispatcher when train operation is in some trouble so the driver can pass it on to the passengers to put their minds at ease, or so the driver can contact the nearest stationmaster to ask for emergency arrangements if a passenger is suddenly taken ill on board.
There are 3 types of train radio systems: A type is a duplex system adopted for dense traffic commuter sections in the metropolitan area, the B type is a semi-duplex system for general sections in large city areas, and the C type is a simplex system for other sections.
