Pulse Code Cab Signaling

The Pulse code cab signaling is a common train control system the United States, the term " pulse-code - modulated cab signaling ". In the basic version, it transmits as the itialienische RS4 Codici four driving terms. This " 4 -aspect system " was introduced in the 1920s by the Pennsylvania Railroad Company Railroad.

History

In 1922 the Railway Inspectorate Interstate Commerce Commission decided that trains future may not drive more than 80 miles per hour without an automatic train protection. The railway company Pennsylvania Railroad took this as an opportunity to introduce a continuous cab signaling, and instruct the suppliers Union Switch & Signal with development.

By 1927, the tests were developed enough that one could define a display with four driving terms. Originally, the train driver should implement the change with restriction acknowledge (without the Quitting would be an automatic braking occurred), but it later developed for the passenger operating a speed trap for vehicles ( "Clear" = unlimited, " Approach Medium" = rapprochement with up to 45 mph, " approach" = slow approach with up to 30 mph, " Restricting " = shunting of up to 20 mph).

Pennsylvania Railroad then installed systems on its routes from Pittsburgh to Philadelphia and New York to Washington. Adjoining companies took over this command and the system has quickly become the de facto standard in the U.S., including advanced and compatible systems.

Function

Into the rail 100 Hz signal is fed, the injection follows a pulse code. A keying of 180 pulses per minute is (free / unlimited distance ) for " Clear", 120 pulses per minute correspond to " Approach Medium" ( drive slow ), 75 pulses per minute is " Approach" (slow convergence ) and 0 ( no pulse ) for " Restricting " ( shunting to view).

This rough division was not sufficient for some applications, such as in heavy traffic cycle of urban rapid transit and at the approach of heavy trains to the frequent curves on mountainous routes. So we introduced a further pulse - code with 270 pulses per minute, and sent in parallel pulses at a frequency of 250 Hertz. This allows more granular speed limits to be defined. The command in the North - East corridor since the 1990s works in the following assignment:

Note the backward compatibility with the 4 -aspect system - only when using the 270 keying creates an incompatibility, but this is only applied in the area of ​​New York Penn Station, and there is derived from the use of Long Iceland Railroad trains.

Extensions

The Pulse - code system has been provided with various extensions, both for the operation of urban rail networks as well as high-speed traffic. However, these extensions are incompatible with each other, they have only the lowest common denominator with the 4 -aspect system.

The function of the cab was a result of the railway accident at Chase in 1987 to a speed trap LSL ( " locomotive speed limiter" ) supplements - while the signals otherwise only produce a sound that must be acknowledged, at the LSL a braking curve is monitored with computer assistance (see PZB Restrictive mode).

The U.S. Congress has demanded in 2008 that by 2015, a unified Positive Train Control system is introduced ( Rail Safety Improvement Act, published on 16 October 2008). There was then still discussions since the decision an " unfunded mandates " (that is no financial support from the federal budget includes ), but the railway authority ( Federal Railroad Administration ) has clearly emphasized the positive cost -benefit ratio on 12 January 2010 the railway companies committed to implementing.

In a statement, the Union of Railways AAR ( Association of American Railroads ) in this respect to the existing Acses (Advanced Civil Speed ​​Enforcement System) is referenced, that was installed by Amtrak for the high-speed rail in the Northeast Corridor (tested from 2000 to 2002 between New Haven and Boston, subsequently to Washington extended ). That system is based on eurobalises, but it is to be distinguished from the European ERTMS, as the driving terms of the Pulse code cab signaling currently have no precedence and GSM -R will be used. In particular for freight is also under discussion, to abandon the position report of beacons and to work with Differential GPS. These elements are then combined in a novel PTC system.