Railroad Signals

2.  Used to prevent train collisions  Collisions are a major concern as trains travel on fixed paths  A freight train travelling at 55 mph takes over a mile to stop  A train will not be able to stop before hitting an object after the engineer sees it

3.  Early signals were flags or lamps placed at a predetermined stopping distance from an obstacle  Used before stations and draw bridges  Only other control system was by timetables

4.  Began in the 1830s  Balls of different colors and shapes were raised and lowered to show “Safety” or “Danger”

5.  Began in the 1840s  Several designs  Different shapes or colors described specific situations

6.  Tracks divided into sections known as “blocks”  Used to space trains far enough apart so they could not collide  Signalmen were stationed at the beginning of each block and changed the signal  Signalmen sent telegraphs to confirm when trains passed  Widely used after 1850

7.  Often used to tell an engineer they need to stop and receive a telegraph  Common in 1870s  Downside was colors were not standardized  Originally white used instead of green as green was difficult to produce

8.  Allowed automatic signal operation from long distances  Created closed-circuit tracks by using the rails as conductors  Original idea in 1872, but at the time was not able to power a signal

9.  Previous signals hard to distinguish from long distances and only able to be seen during day  Position signals introduced in 1920s  Red, yellow and green lights added in 1950s

10.  Electrical currents in tracks determines if block is occupied  Block lengths may be variable and computer- generated  Signal is green if next two blocks are unoccupied  Yellow if second is occupied  Red if next is occupied

11. •Salary: $51,000 - $61,000 •Education: Bachelor’s •Experience: 0-2 years Civil Engineer •Salary: $56,000 - $65,000 •Education: Bachelor’s •Experience: 0-2 years Electrical Engineer •Salary: $50,000 - $57,000 •Education: Bachelor’s •Experience: 4 years Geotechnical Engineer •Salary: $30,000 - $39,000 •Education: High School Diploma/G.E.D. •Experience: 0-2 years Welder •Salary: $26,000 - $34,000 •Education: High School Diploma/G.E.D. •Experience: 0-2 years Heavy Assembler

12.  Designs and supervises construction projects such as airports, bridges, channels, dams, railroads and roads  Responsibilities also include estimating costs and personnel and material needs, preparing proposals and establishing completion dates

14.  Designs, tests, installs and maintains large- scale electronic equipment or machinery for use in manufacturing or power generation or transmission  May use computer-assisted engineering and design software and equipment to perform assignments

16.  Prepares and inspects projects involving drilling and exploration  Responsible for geological mapping, report writing, site characterization, numerical modeling and analysis of excavations/supports

18.  Joins, fabricates and repairs metal and other weldable material by applying appropriate welding techniques  Interprets blueprints, specifications, diagrams or schematics to determine appropriate welding process  Inspects completed welds to determine structural soundness

20.  Assembles fabricated parts to relatively large or heavy subassemblies and complete units  Tests and calibrates parts and mechanisms to meet tolerances and product specifications

21.  Characteristics of electrical circuits  have a closed loop  have a full, circular path  Today’s activity is to build basic circuits with batteries, switches and lights  There are two ways to wire lights:  Series – if one lights go out, both go out  Parallel – possible for one light to work while other does not  One will give you brighter lights than the other

22.  The green screw on the light switch is a ground, do not use this screw  Don’t attach both wires to the same end of the battery  Turn the switch to off until you are done wiring, it makes it easier to see how bright the lights are

Railroad Signals

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Railroad Signals