block system

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Newt. Salamanders. Amphibian. Alpine newts. Ichthyosaura alpestris. Caudata. Urodela. Alpine newt swimming underwater.

Deviously Darwinian: 6 Strange Evolutionary Phenomena

Scolex (head) of the tapeworm Taenia solium. The hooks of the scolex enable the tapeworm to attach to the intestinal wall.

Uninvited Guests: The 7 Worst Parasitic Worms

Comparison of a hare and a rabbit. (Left-hare) black-tailed jackrabbit (Lepus californicus); (right-rabbit) desert cottontail (Sylvilagus audubonii)

What’s the Difference Between Rabbits and Hares?

King Cobra snake in Malaysia. (reptile)

9 of the World’s Deadliest Snakes

Figure 13: A Maxim machine gun, belt-fed and water-cooled, operated by German infantrymen, World War I.

7 Deadliest Weapons in History

Black widow spider

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The impeachment trial of Pres. Andrew Johnson, illustration from Frank Leslie's Illustrated Newspaper, March 28, 1868.

What If the President Is Impeached?

block system

railroad signal

Learn about this topic in these articles:

railroad operations and safety

In railroad: Signaling
In these so-called block systems, a train is prevented from entering a specific section of track until the train already in that section has left it.
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railroad signal

In railroad signal
They were improved into the block system, by which the distance interval between trains was constantly recorded. The introduction of electric power brought increasing automation to block signalling. In modern automatic block signalling the axle of a train entering a section of track on which another train is running shorts…
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