I suppose it might work, but . . . .
There are always other options like RFID or barcodes on the bottom. That would definitely require a computer, the Digitrax boards and throttles would not know what to do with the info from one of those sensors. RFID can be very reliable but even the short distance sensors and tags is probably too sensitive for a row of tracks at standard HO spacing - it may pick up what's on the adjacent tracks as well. Barcode, not sure how to make sure that is reliable and stays reliable, not every loco has a nice flat spot on the bottom, and the speed will vary. One reader per track and you'd be all set - reader 5, track 5, reads loco number 1234. Now you know the start position, the Train Tracking can follow it when you pull out onto the railroad.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Jim, Randy, thanks as always. Whereas non of my decoders are Digitrax, and I am not about to start putting a second decoder in my engines, I guess I'm resigned to using the BD168 and LEDs for block detection and a paper form on a clip board to know what engines occupy my hidden tracks. At least I now won't need to have my laptop running all the time.
For automation purposes, RR&Co and JMRI both have the capability to 'track' a train. Knowing the starting location, assuming all turnouts are under DCC control, or at least can report their position back (say like with contacts is using ground throws) then it's not too difficult to see how the computer can 'know' where a given train is after just being told its starting point. It will see the blocks go occupied, and it will see which route is taken at each turnout, so it therefore can extrapolate just where on the layout the train is. No transponding.
The thing about Transponding (and also with Railcom, Lenz's version) is that we are back to the same issues that early command control systems had, namely a little tiny signal getting swamped in the electrical noise of the railroad. Since the transponding signal is being generated by the decoder, it can't be a very strong signal, there's not a lot of power available to generate it. Lots of people have gotten it to work in trvial test setups (simple ovals, that sort of thing). A FEW have gotten it to work on a more complex layout. You also have to be careful what decoders you use - if you have non-Digitrax you would have to add one of their transponding decoders as a second decoder, but also not all decoders are compatible with Transponding from the fact of being on the rails and connected. Soundtraxx is one of the few. Other sound decoders with large stay-alive capacitors will probably just eat the Transponding signal.
Digitrax decoders have the 'transponding' built in. Digitrax sells 'transponders' you add to locomotives that have other makes of decoders. Go to the Digitrax web site and look at the TL1 transponding only function decoder.
If you do not need to know the engine number of the locomotive on your staging track(you just need to know if the track is occupied), then the BDL168/RX4 solution may work for you.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
In another Post regarding an issue Dano had with his DB150 (I didn't want to steal his post), Randy, you replied to Dano that transponding is only possible with Digitrax decoders. Might you help me better understand transponding (my apologies for my lack of understanding on this subject . . . well OK, most every subject!)? Here's my short story long: I am in the midst of building a 9 track hidden staging yard under the layout. Last month at the Springfield show I spoke with the Digitrax folks and they said by using a BD168 (which in a previous post you had already suggested) along with some RX4's I could report the addresses of the engines occupying the tracks via LocooNet to PR3 to JMRI PanelPro. But they never mentioned it only works with their Digiytrax decoders! So if I understood you correctly and only Digitrax decoders will work, is there another way of accomplishing my goal, using other products to report to the PR3 and JMRI? As always, I appreciate everyone's input.