I am employed ay a railroad and have worked as part of a train crew
(brakeman, conductor, and student engineer). The EOT device comes in two
flavors- a 'smart' EOT (end-of-train) device and a 'dumb' EOT.
The dumb EOT is just a device that functions as a marker (red flashing
ight required 1/2 hr before sunset to 1/2 hr after sunrise- the dumb EOT
turns on and off the marker light by means of a photoelectric cell).
The 'smart' EOT sends the following data to the locomotive:
1) rear of train brake pipe pressure (must be at least 60 psi to be legal)
2) tells when rear of train is moving, so engineer knows that the slack
is stretched (there is a mercury switch inside the EOT that performs this)
3) tells if front to rear communication is lost
4) alerts engineer when batteries are low in the EOT
5) on some 'smart' EOT's, there is a feature whereby the engineer can
initiate a dump of the air in the brake pipe from the rear. The EOT
exhausts brake pipe pressure when the engineer throws a switch on the
companion EOT device in the locomotive (the in-cab unit is commonly
referred to as a 'wilma' and the rear device is often called a 'fred'.
Most EOT devices send a signal back to the front unit approx every 45
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