The most complete family of Computer-Based Interlockings for rail and transit is only available from Hitachi Rail STS. ACC, SEI and MicroLok® provide the perfect solution for networks and stations of all conditions, be it High Speed, Main Lines, Freight or Metros. Their integration with Centralized Traffic Control (CTC) and with Automatic Train Protection (ATP) systems has also been proved in High Speed applications.

ACC provides complete route control in a single machine with ‘area controllers’ able to continue local operation in event of gross communication system failures. It supports an integrated axle count function and provides detail diagnostics for attached objects. It takes dependability to new levels for example through support for 2 out of 4 redundancy where competitor systems only support a 2 out of 3 approach.

SEI provides mid-range interlocking needs and supports a full relay-based interface to controlled objects to provide for intelligent life cycle management.

MicroLok II is Hitachi Rail STS’s ‘safe plc’. It provides low cost user-programmable safe system delivery through a distributed architecture that does not require a controlled environment and so can be deployed in lineside cases. Each of our systems is supported by a suite of tools and related products.

Among the many Interlockings installed internationally, Rome Termini Station represents an unmatched state of the art achievement. Rome Termini lies at the very heart of the Italian railway system, managing the complexity and capacity of a network of thousands of kilometers with an Interlocking capable of safely controlling the traffic of most of Italy from one single control room.

Computer-based Interlockings by Hitachi Rail STS are currently in use all around the world, including the most demanding High Speed networks (France, Italy, Spain, UK, Belgium, China or South Korea); on Main Lines (US, Italy, France, Sweden, India, China, Bangladesh, Botswana, Malaysia or Australia among others); and also in metros.



ACC Computer-based interlocking, is a modular system for railway and metro applications that can control the operation of very large and complex track layouts with high traffic volumes.  Operation execution times are assured including at times of peak traffic demand. Developed by Hitachi Rail STS, ACC can control all vital applications used in railway signalling and train traffic control.
This system can carry out automatic diagnosis, operator assistance and data recording to maximise the efficiency of both the signalling operators and maintenance staff .In addition to normal self-diagnostics, It is equipped with a detailed monitoring facility for attached equipment, which detects equipment malfunctions and can support predictive maintenance interventions.
The availability of these automated tools for design, testing, fault finding and maintenance significantly reduces the implementation times and general plant costs.
ACC software can be configured and adapted to various types of signal control and operational rules as may be required by different infrastructure managers.

The main features of ACC architecture are its modular structure and redundant processor configuration. These qualities support the implementation of the route control, interlocking functions, and traffic control features needed to comply with security regulations, fault tolerance requirements and availability specifications. This can include support for multiple redundant processors and communication channels to satisfy requirements for ultra-dependable operation.
The architecture is based on a hierarchical processing system that enables sub-systems to be configured on the basis of the various applications and according to their operating capabilities. This is the ideal environment in which to develop vital systems.
The basic hardware and software structure ensures secure operation while the application modules add specific functionality.

The system is made up of a central post and peripheral units, which may be adjacent to each other or located far apart. The central post is the site of the central interlocking unit that carries out vital operations on a majority vote basis, together with other systems that have non-vital, auxiliary functions. The central post has user interfaces that can be configured for both operators and maintenance staff. The peripheral units provide local power to controlled objects, and include object control devices optimised to interface to particular signals, point machine, and train detection products in order both to provide relay-free solid state interfaces and to deliver diagnostic information on these objects.  This tight integration delivers real system whole-life benefits.

The architecture of the new-generation ACC systems cuts design, installation, operation and maintenance costs. Design cost is minimised through re-usability and automation.  Installation cost is minimised through appropriate distribution of functions and avoidance of equipment close to running lines where installation costs increase. Operational efficiency comes from delivery of functionality such as full bi-directional operation maximising the availability of the controlled infrastructure.  Thanks to advanced maintenance and diagnostic functions, the system can monitor its own status and generate reports, and thus efficiently manage functional faults, technical failures and alarms. Maintenance operations can be planned on the basis of the system’s self-diagnostic tools, and most interventions may be carried out remotely, with few staff and no slowdown in traffic.

The system is configured extremely flexibly and can be adapted to any type of line. It can be installed regardless of the type of traction, line speed or track gauge; it can control an indefinite number of stations and lines of any length. Boundaries of control are placed where the owner wants them for operational reasons, not where the system dictates.


Hitachi Rail STS’ SEI interlocking provides continuous line of route control and interlocking functions. The safety processor core is designed using ‘2 out of 3’ digital technology able to interface up to 200 object controllers (MTOR product line) with each object controller in turn supporting interface to up to 20 objects. SEI supports open standard data communications interfaces and thus is able to take advantage of modern hierarchical digital telecommunication system infrastructure without requiring dedicated cables between the central safety processor and its associated object controllers. Placement of the object controllers units near to the controlled objects makes this system easily adaptable to various rail network types. The functions carried out can be remotely checked by the control centre or via a local control station.

SEI can integrate with our RCC supervisory control centre signaller’s interface, and with both ERTMS/ETCS and TVM train control systems.

For ERTMS SEI supports a bi-directional data interface to the matching Hitachi Rail STS RBC equipment thus enabling functions such releases of approach controls and maximising the capacity gain that ERTMS level 2 can deliver.

When applied in combination with Ansaldo STS TVM430 Automatic Train Control, SEI supports all of the TVM 430 functions: continuous speed and headway control, and cab display using continuous track to train transmission. The greatest innovation consists in the integration of the ATC ("Automatic Train Control") and the IXL (Interlocking) within the same computer platform.

By integrating these functions, this system considerably reduces the usual interfaces necessary between the two systems: the ATP ("Automatic Train Protection") on one side, the interlocking on the other, and enables a significant reduction in the project cost and risk.

Maintenance efficiency is enhanced by comprehensive event recording and provision of decision support tools.

Computerized “parameter generation” tools allow the automatic management of each sub-system’s parameters, as well as test and simulation tool parameters. This range of configuration tools reduces the signalling study work and reduces the effort and thus the cost of factory and site testing.

This SEI system is the only one of its kind on the market, integrating on the same processor the interlocking and ATP functions.


The first vital microprocessor-based interlocking in North America was installed on Conrail’s Esplen Interlocking in 1984, shifting vital relay technology to a new level of efficiency.

Today, our MicroLok® technology continues to provide superior wayside monitoring and control with new systems and components that lower costs and reduce energy consumption.

MicroLok® II Interlocking Control System is a multi-purpose monitoring and control system for rail and transit wayside interlocking equipment. Its wide range of functional capabilities include vital interlocking control, non-vital code system applications, train detection, rail integrity, coded track circuit communication and more. Easy-to-use programming tools allow configuration to meet the specific requirements of the intended application.

Features and Benefits
Wide range of capabilities eliminates the need for space-consuming vital logic relays.
Peer protocol (open specification) allows simultaneous communication to multiple units.
Continuous internal diagnostic function logs history for later review.

MicroLok® Object Controller (OC) is a low cost, programmable microprocessor device for vital and non-vital control and indication of wayside devices. This self-contained remote I/O device is programmed to meet the specific needs of the intended application. Its compact size reduces power consumption.

Features and Benefits
Fully integrated TCP/IP port for vital and non-vital Ethernet communication Compact, rugged design fits into a wayside junction box and allows quick replacement in the field Web-based tools enable users to monitor and troubleshoot via Internet Explorer I/O wiring is terminated into a Wago plug connection eliminating the need for intermediate termination points.