DCC ImpulsesColumn - 6
OK, nowwehaveaway to tell that theblock isoccupied.What
dowedowith this knowledge?
Signal animator
A signal animator is a relatively simpletimer circuit activated
by theblockdetector.When theblock isoccupied, theanima-
tor sets the signal to the stop (red) aspect.When theblock
clears, theapproach (yellow) aspect is set. After theapproach
aspect hasbeendisplayed for aperiodof time (usuallyuser
adjustable) the signalmoves to clear (green).
Anoperator running a through train and following traffic can
use these signals to knowwith relative certainty that the
block ahead is clear (yellowor green). In the real world, a
greenwould assure that the secondblock aheadwas clear,
aswell.With a signal animator, information from the second
block ahead is not shared. Thus, theengineer doesn’t have
100% certainty that hehas two clear blocks.
As great as the concept
seems, today therearenot a
lot of choices in readybuilt
hardware to implement it. A
tinkerer could always build
his owntimer circuit and
activate itwith anoff-the-
shelf DCCblock detector.
Atlashas anice system that
has even some realistic signal
heads
. This sys-
tem seems tohavebeen lost
in theMade-in-China issues
over the last fewyears. It is
reasonablypriced, but not
7: AzatraxMRD2optical
detector senses twoplaces
in the block. Photo courtesy
of Azatrax.
7
currentlyavailable. Stores, swapmeets, andeBaymight yield
someold stock. Hopefully, itwill soonbeavailableagain.
NCEpromiseda system called ( SIG12 )manyyears ago. As
I understand it, the signal animator portionof theSIG12
worked just fine. However, the folks atNCEwanted to include
the sophisticationof aneasy-to-install system thatwould sig-
nal that secondblockahead, too. Thus, a clear signal (green)
wouldguarantee that thenext twoblockswere clear. Getting
all this toworkunder a lot of conditionshasn’t yet happened
and theunit remainson the shelf.
Signaling the entire pike
Sophisticated signaling systems take intoaccountmore than
just occupiedblocks. Turnout position comes intoplay, too.
Consider a scenariowhere themain track in thenext block
isoccupied. A signal animatorwouldgivea stop (red) signal.
However, if youhavea scheduledmeet andyour partner is
already in theblockon themain, youbothwill see stop signals
8: BLMA signal bridge (4025a) inHO-scale. Photo cour-
tesyBLMA.
8
MRH-Apr2014
