Signals & Switches

Railway centralization is designed for controlling all the switches and signals, in a railway station or its area. Control is exercised from a single control point to the entire system. In order to know the traffic condition on tracks, rail circuits work as sensors. more...

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And sometimes they are used as signal transmitting media.

Needs and requirements of station trackage centralization

The speed of train processing at the stations plays a major role in railway permitivity. Railway safety highly relies on station operation. Switch and Signal Centralization is a kernel of stationary automation. Centralization provides logical interaction and blockage in accordance to safety standards, as well as economical and beneficial switch and signal control within a distance.

Nowadays railway centralization is implemented by means of Electromechanical circuits, sometimes with a help of electronics and microprocessors. The general requirement is to be reliable and work without mistakes and failures. If a system fails, it must fail safely. Safety failure, is such a failure which can result in more prohibitive state of a centralization system. (i.e. Red light instead of Green) Unsafe failure is when a systems fails giving more permissive state then it should (Green or Yellow instead of Red) it is called an . Anything that may lead to unsafe failure, which threats 1000s of lives should be avoided (even though preventing from more advanced level). Failures must be safe, whenever they occur. Safe failure may cause delays, but no threat at all.

Anything that can lead to a failure of a system, (i.e. bad contact, operator's malpractice), should never cause an unsafe failure. That's why all the equipment ranging from relays and switches, should rather fail (not work) than to work wrongly.

Routing through station

When station entrance trackage allows multiple routes from one point to another, basic route is a shortest path. It has the minimal number of crossing with other tracks, and allow the maximal speed.; Any other route is called a variant route.;

Acceptance route provides train moving from the stretch to the station tracks.; Transfer Routes is for train which move from one station track to a consecutive.; Departure Routes allow trains to go from a station track to the consecutive stretch; Shunting Routes move the rolling units which are not ready to work in trains;

Technical Characteristics of Centralization

First there were mechanical systems, where the signal and switch transition were done mechanically, using the traction string laid under station from the control point to the switches and signals. Signal and switch control was done by hand, and blockage was done using special portable keys (key dependency)

Read more at Wikipedia.org