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QUOTE RS485 meets the requirements for a truly multi-point communications network, and the standard specifies up to 32 drivers and 32 receivers on a single (2-wire) bus. With the introduction of "automatic" repeaters and high-impedance drivers / receivers this "limitation" can be extended to hundreds (or even thousands) of nodes on a network. RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off. Also, RS485 drivers are able to withstand "data collisions" (bus contention) problems and bus fault conditions.

So as I understand it Xpressnet is currently limited to 32 devices, and this would include
handhelds, boosters,automatic reversing modules, stationary decoders, and the like, so it's quite possible on a large complex layout to reach the capcity of the system ?.

I ask this because I have no practical experience of the Lenz system. Several of our club members are considering a change to DCC. In past discusssions with a large group of Digitrax users at another club, it was always stated that Lenz were not ideally suited to larger walk around layouts. I never fully understood why. I naturally assumed that if you had a cab bus you could simply hang more devices on it as it expanded, as you can with Loconet. Do similar limitations exist with other systems ?.
 

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I've seen massive modular layouts in both Ntrack and HO. Again the only control system has been Digitrax on these layouts. Mainly because South Africa is largley Digitrax due to the poor support for Lenz, and others.
But while I'm talking: with Digitrax each addon to the cab bus be it: booster, reversing module, stationary decoder, PM42, BL16, Handheld & UP5, is connected to loconet or the cabbus system surely Lenz works the same way?.
While I accept that most British layouts at home arn't that big, times are a changing. My
own local branch of the NMRAUK has a large modular layout, yes I'm currently making the switch to American HO. I believe modular layouts must catch on, as they offer so many advantages. The problem then is how to control them. It would seem to me that the only suitable system in DCC (for large layouts) is Digitrax as you simply daisychain the loconet between devices.
I was considering trying Lenz for a smallish shunting layout in my study to save me having to slep controllers from my main layout, but I think I'll go Zephur, as it's compatable with my trottles.
 

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Thanks for that, I truely believed Xpressnet worked in a similar fashion to Loconet.
Now I appreciate the difference. I assume the feedback bus is daisy chained back to the control station ?. So the weakness with the Lenz cab bus system is it's single direction only.
I still think it's a great pity no standard for cab-bus was developed by the NMRA.
 
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