The objective of a modern signalling system is not only to secure the safety of high-speed high-density train operation, but also to contribute to the rationalization of railway management. A signalling system is mainly comprised of block systems, signals, interlocking equipment, point switching devices, train protection devices, level-crossing protection equipment, centralized traffic control system (CTC) and computer-aided traffic control systems.
A rough history of signalling in Japan is as follows:
1872 - 1887 Establishment period
1887 - 1903 Mechanical interlocking / Semaphore signal
1904 - 1925 Electro-mechanical interlocking
1926 - 1954 Electric interlocking / Color light signal
1955 - 1984 Relay interlocking / Color light automatic signal / ATS
1985 - present Electronic interlocking / ATC for commuter sections
After World War II, Japan National Railway strongly supported a modernization program adopting electrification and automatic signal systems to achieve high-speed and high- frequency train operation. Semaphore-signals and mechanical-interlocking systems were replaced successively by color-light-automatic-signals and relay-interlocking systems. The ATS (Automatic Train Stop) system (ATS-S and ATS-B type) was introduced nationwide in 1966.
The "fail-safe" theory was established mainly in the relay-interlocking period, and contributed greatly to the safety and frequency of train operation. More complicated systems such as RC (Remote Control) and CTC (Centralized Traffic Control) systems using relays were introduced in some sections, however, did not spread nationwide until microelectronics devices appeared.
The Tokaido new trunk line (Tokyo-Osaka, gauge: 1435 mm) was constructed in 1964, and brought in the first all-solid-state CTC, ATC (Automatic Train Control) systems and other electronic devices. The COMTRAC (Computer-aided Traffic Control) system was introduced when the line was extended to Okayama in 1972. Thereafter, these devices and systems were improved as new electronics technologies were adopted, especially the microprocessor, and also have been applied rapidly to existing lines (gauge: 1067 mm).
The CTC system, allowing reduced numbers of station personnel, was spotlighted as a means of rationalizing railway management and spread nationwide. In order to apply it on local lines, all-out efforts to develop a simple and low-cost CTC system were made at the time. Several types of PRC (Program Route Control) systems were also developed to keep pace with the CTC system.
