How does block detection work with DCC? : LUSENET : Wiring for DCC : One Thread

If the premise of DCC is to run the train not the track, doesn't that make the "old" idea of indepenant blocks disappear? I mean that if you layout is basically a big loop.. then you simply attach the DCC wires to the track and go? If that is the case, then the WHOLE layout is one block, and even if you broke it up into sections of insulated track, the fact that a single power source is connected to all the "blocks" negates that even...

-- Dave Sisemore (, March 27, 2002


You are right David. With DCC you don't really need to break up your layout into multiple blocks to run 2 or more trains independantly. [Except for reversing track loops] That's the beauty of DCC.

So why would you want to break up the layout into smaller track blocks by providing insulated gaps between sections? 1. For big layouts with lots of trains it may be necessary to use several 'booster dictricts' as one booster cannot power all the trains at once. By breaking the layout into several separately powered districts each booster supplies power to only the trains in it's district. Each track section has the same signals to control trains as each booster simply repeats (boosts) signals from the same DCC control station. 2. For multi-operator layouts it is convenient to break up the layout into several smaller sections, each with it's own circuit breaker. This may indeed be powered from the same or separate booster. The reason is to avoid one operator caused derailment from shutting down the entire system. 3. If you want to use a remote dispatcher or automatic signaling system, it requires knowledge of where trains are located....One of the ways to do it is to break up the track into isolated signal block sections, and then measure electric current feeding each electrically isolated track section to determine if that block is occupied by something that draws current. Although the source of power may be from the same booster, a current detector is placed between booster and rails to determine occupancy. 4. Even on small layouts it may be convenient to have track staging stubs or sidings with a toggle switch to remove track power. This is a positive way to prevent train movement by an operator selecting the wrong engine. 5. Power routing switches (turnouts) can cause momentary or permanent short circuits with certain track combinations. And just like w/ DC throttles, isolating rail gaps resolve the issue.

If you don't need any of the above, you don't need any isolated track sections.


-- Don Vollrath (, March 27, 2002.

I would like an answer to this question also for signaling purposes.

-- Norm Bell (, May 16, 2002.

Norm, See #3 in my response above. Each signal protects a section or block of track. Each signal block has a track occupancy detector. In brief, the signal at an entrance to any particular block would show a 'red' signal if that block is occupied.

There is much more to it than that. There are several good sites that explain RR signaling in much more detail. There are many ways to do it on your model RR.

Here are a couple of sites worth digging into for a good understanding.

You also may want to sign up for the railway-signaling group in Yahoo!


-- Don Vollrath (, May 20, 2002.

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