The number of blocks can depend on several factors. How many blocks YOU want, and / or the length of the trains that you run on your railroad.
I set the length of my blocks to be between 1-½ and 2 trains long. This means that you should have in mind how long the trains you want to run will be. This is not an absolute length because some turnout locations on your track plan may have an affect on block length.
My longest train is 9 cars plus loco and caboose, so figure 11 cars. So my blocks are between 14 and 19 cars long. (I figure 6 inches for each 40 foot car.)
The following link may help:
http://www.waynes-trains.com/site/Signals/GettingStarted/SignalsGettingStarted1.html
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
The BDL16 is outdated, it has been repalced with the BDL168 which supports two RX4's, the BDL16 only supports 1. Note that this still means 16 total block detections zones but only 8 transponding zones.
You absolutely MUST follow the directions EXACTLY when it comes to the physical layout of the BDL and the RX4, they are EXTREMELY sensitive and if other wires get within the clear space required by theinstructions they WILL fail to work properly.
If you have RR&CO - there really is no need for transponding. Train Tracking works very well. A friend of mine uses this to automatically run 4 trolleys around his town without them crashing into one another.
To just have trains run by themselves, you might get away with just 16 detected sections, but with that double main plus the cutoff, and to do actual prototypical detection and signalling such that the area around a turnout is detected for interlocking, not part of either the approach route or either diverging route (ie, a passing siding would be SIX detection sections just by itself - east approach main, east turnout, main between turnouts, siding betwee turnous, west turnout, and west main) will need a LOT of detection sections.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
This is a map of my current model railroad. I'm getting a Digitrax BDL168 occupancy detector. I already have a Digitrax SE8C, a Digitrax DT402D throttle, a DB150 hooked up to a PR3 through Loconet and to my PC via USB. I have Railroad and Company and Java Model railroad Interface software. According to this map, which sections should I detect how many blocks. All my trains have Digitrax decoders with sound and transponding.Will one BDL168 do the job or will I need more. Do I also need a Digitrax RX4 4-Zone Transponding Receiver? If so about how many will I need? Are switches the most important part of the blocking in order to cooperate with the signaling?