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Signal types. North American signals are commonly of three types. Absolute – Absolute signals are usually connected to an interlocking controlled by a block operator or train dispatcher. Their most restrictive aspect is "stop" and trains cannot pass them at stop unless they obtain special authority.
In 1992, the American Association of Railroad Superintendents (AARS) convened a special committee, which suggested to its board of directors, executive council, and membership that “the AARS sponsor a full conference on the standardization of railroad operating rules, practices, and procedures, and that this conference be conducted on the ...
CBTC is a signalling standard defined by the IEEE 1474 standard. [1] The original version was introduced in 1999 and updated in 2004. [1] The aim was to create consistency and standardisation between digital railway signalling systems that allow for an increase in train capacity through what the standard defines as high-resolution train location determination. [1]
Railway semaphore signal is one of the earliest forms of fixed railway signals. This semaphore system involves signals that display their different indications to train drivers by changing the angle of inclination of a pivoted 'arm'. Semaphore signals were patented in the early 1840s by Joseph James Stevens, and soon became the most widely used ...
Pulse code cab signals work by sending metered pulses along an existing AC track circuit operating at a chosen carrier frequency. The pulses are detected via induction by a sensor hanging a few inches above the rail before the leading set of wheels. The codes are measured in pulses per minute and for the 4-aspect PRR system are set at 180 ppm ...
Automatic equipment identification (AEI) is an electronic recognition system in use with the North American railroad industry. Consisting of passive tags mounted on each side of rolling stock and active trackside readers, AEI uses RF technology to identify railroad equipment while en route. RFID antenna used by trackside AEI readers.
Centralized traffic control. Centralized traffic control (CTC) is a form of railway signalling that originated in North America. CTC consolidates train routing decisions that were previously carried out by local signal operators or the train crews themselves. The system consists of a centralized train dispatcher 's office that controls railroad ...
Cab signaling is a railway safety system that communicates track status and condition information to the cab, crew compartment or driver's compartment of a locomotive, railcar or multiple unit. The information is continually updated giving an easy to read display to the train driver or engine driver. The simplest systems display the trackside ...