Evolution
The first FRED use is attributed to Florida East Coast Railway in 1969, soon other Class I railroads began using FREDs as well, until the mid 1980s when they were common equipment. Early models were little more than a brake line connection / termination, a battery and flashing tail light. As their use became more widespread through the 1980s, FREDs were equipped with radio telemetry transmitters to send brake pressure data to a receiver in the locomotive. To reduce the cost of battery replacements, ambient light sensors were added so the flashing light on the FRED would illuminate only during dusk and after dark. Later models have a small turbine-powered electrical generator using air pressure from the brake line to power the FRED's radio and sensors.
The one-way communication of brake data from the FRED to the locomotive evolved into two-way communication that enables the engineer to apply the brakes from both ends of the train simultaneously in an emergency. This is useful in the event that a blockage (or an unopened valve) in the train's brake line is preventing dumping the air pressure and causing all of the brakes in the train going into an emergency application. Such a situation could be dangerous, as stopping distance increases with fewer functioning brakes. Dumping the brake line pressure from both the front and rear of the train simultaneously ensures that the entire train applies all of its brakes in emergency. Other electronics within the FRED were also enhanced, and many now include GPS receivers as well as the two-way radio communications.
Read more about this topic: Flashing Rear-end Device
Famous quotes containing the word evolution:
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)
“The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (1820–1903)
“Like Freud, Jung believes that the human mind contains archaic remnants, residues of the long history and evolution of mankind. In the unconscious, primordial “universally human images” lie dormant. Those primordial images are the most ancient, universal and “deep” thoughts of mankind. Since they embody feelings as much as thought, they are properly “thought feelings.” Where Freud postulates a mass psyche, Jung postulates a collective psyche.”
—Patrick Mullahy (b. 1912)