Bob, With DCC all your track can be one block, with the exception of reverse blocks. These require gaps in both rails at each end and can be powered thru reverse modules. Several manufacturers make them, in two basic styles I'm aware of. Before I go into the reverse modules, you should be aware that DCC systems (basically) consist of: a cpu (command station), boosters, throttle and decoders. A good site to visit is
www.loystoys.com Some systems combine the command station and booster. I am only familiar with Digitrax, which has seperate units. OK, the first method of reversing trains uses a second booster, dedicated to the reverse block. It can operate more than one reverse block, but only one at a time, meaning that only one train can be entering or leaving a reverse block at a time. Other trains can be within a reverse block, as long as they do not enter or leave simutainuously. The other (automatic) method is reverse modules (I use the ones by Tony's, see
www.ttx-dcc.com ) MRC also makes one, I do not like them. Both methods automatically change polarity of the reverse blocks power whenever a wheelset crosses the gap from the main. This happens so fast that circuit breakers do not see the temporary short. Locos do not change direction when the polarity changes because with DCC you tell the loco to go forward or backward with the throttle, the decoder applies power accordingly regardless of the input polarity. Direction of travel is not the reason for changing polarity, it must still be changed to aviod shorts. The MRC modules are not as fast as Tony's, and often would not work at all with steam locos which do not pickup power with the lead truck. Diesels lacking all wheel pickup would probably exhibit the same performance. I use Tony's on a total of 11 reverse blocks on my layout, they work flawlessly. The modules are wired as follows: Two wires in from track power bus (polarity doesn't matter), two wires out to reverse block (polarity doesn't matter). It really doesn't get much simpler. You should also check the Digitrax page at
www.digitrax.com There are a lot of extras you will see, I do not use them. I am not a computer type of guy. One more thing for now, although you can wire the layout as one block (except for reverse blocks) you may want to break it into two or more just for troubleshooting (you can disconnect blocks to find that mysterious short someday) Check out the websites and let me know what you think.
Gary