Signal safari part 3 (NW Mailing List)

[NW Mailing List]

Jimmy Lisle wrote:

> Ed Bell wrote:

> > Okay, so can someone explain the differences between 408 & 410?  While 

> > the upper targets are the same, the lower ones are not.

> >> http://nwhs.org/wiki/tiki-browse_image.php?imageId=408

> >> http://nwhs.org/wiki/tiki-browse_image.php?imageId=410

> Ed,

>      Signal 408 is able to display:

> Clear

> Approach

> Stop

> Restricting

> 

>      Signal 410 is able to display:

> Clear

> Approach

> Stop

>      Dependent on trackage beyond, it also has the ability to display:

> Advance Approach

> Approach Diverging

> Diverging Approach

> Diverging Clear

> Restricting


To expand on what Jimmy wrote, signal 408 is the southbound (geographic,
not timetable) signal off the east leg of the wye at Auville.  The
straight route leads to the Dry Fork branch main, while the crossovers
protected by the signal leads into the north end of Auville yard. Since
the yards tracks are not CTC territory, the signal only needs to show
Restricting on the bottom target.  Basically, there is no diverging route
into CTC controlled tracks beyond the control point, it has no need to
display any diverging indication other than restricting. The next mainline
signal is the holdout signal (no switches) at Kelly, so it has no need to 
display Approach Diverging, and since the second signal is 2.5 miles
upriver, it has no need to display an Advance Approach.

Signal 408 is the westbound main 2 signal at Keystone, and protects both
a crossover from main 2 to main 1 westbound and a switch into the east
end of Eckman Yard. The next signal to the west is the double crossovers
and yard switch at Eckman (west end of the yard). This means the signal
needs to be able to show not just Clear and Approach for trains staying
on main 2 and Restricting for trains entering the yard via the crossover
like signal 408, but also needs to be able to show Diverging Clear and
Diverging Approach for trains crossing from 2 to 1 (an staying on 1),
but also Approach Diverging for trains crossing from 2 to 1 at the next
signal, as well as Diverging Approach Diverging (yellow over flashing
yellow) for trains lined from 2 to 1 at Keystone and then back to 2 at
Eckman. Basically, unlike signal 408, it needs to cover not just diverging
routes into a different CTC controlled main but also act as an approach
signal for the crossovers at the next signal.

Being a down grade signal, signal 410 may also be capable of displaying
an Advance Approach indication, but I don't know for certain about that.



Joe Shaw
Christiansburg, VA
http://www.krunk.org/