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DT
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Looking at the new Hornby Digital range of products we see that they use XPRESSNET as a means of interconnection.

This allows us to add supplementary cab control units around our layout. Or, using XPRESSNET, we can use DCC components from other manufacturers that support the standard (see Compatibility bellow).

XPRESSNET is a high-speed multi-point to multi-point digital network based upon the industry standard RS-485 protocol. DCC systems use XPRESSNET to communicate between its high-speed components such as the command station, hand-helds, tower cabs and its computer interface. XPRESSNET communicates at 62.5 thousand bits per second. It is the highest performance network in widespread DCC use and all its protocols are freely available to both the industry and the hobbyist.

XPRESSNET uses 4 Wires - Two wires are for RS-485 and 2 wires are for 12 volt power and ground. These additional wires provide power to the hand-helds when they are plugged in. Providing power lines with XPRESSNET eliminates the need for batteries in our hand-helds or supplementary transformers for remote cabs

What is RS-485?
An Electronics Industry Alliance (EIA) standard for multipoint communications. It supports several types of connectors, including DB-9, DB-37 and RJ-12. RS-485 is similar to RS-422 but can support more nodes per line because it uses lower-impedance drivers and receivers. Line drivers and receivers are commonly used to exchange data between two or more points (nodes) on a network.

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.

We talk of 2 wires, but XPRESSNET uses 4 Wires. And actually the RJ-12 connectors usually house 6 wires.

What is RJ-12?
RJ-12 jacks and sockets are commonly used in telco installations for phones, modems and security installations. The RJ-12 has a 6-pin connector. Don't confuse it with a computer network connector - the RJ-45 that has a 8-pin connector. The RJ-12 jack will fit into a RJ-45 socket, but the RJ-45 jack will not fit into a RJ-12 socket.


The wires for the 6-pin connector are specified as follows:


And this is how they look on the RJ-12 connector jack:


Connecting an XPRESSNET RJ-12socket to a DIN plug (Lenz) is done as follows:


Compatibility
XPRESSNET / X-Bus which is used by Lenz, Arnold / Lima, ZTC and now Hornby allows these units to be interconnected. Generally it is not advisable to connect a master unit from one manufacturer to a master unit from another, but one can use (for example) Lenz hand cab controllers with the Hornby Elite master unit. In this way, if you are used to one type of controller: Lenz, Roco or ZTC, you can still use the new Hornby system. You should be able to use the Hornby Digital Select unit with a Lenz, ZTC or Arnold master unit. We'll be testing this interconnectivity out as soon as possible.
 

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DT
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Lets not make this a "My system is better than your system" topic please.

Loconet has got some interesting features. Non-polled nigh-speed network-like system. Loconet is proprietary to Digitrax and is licensed to about 20 other companies.

XpressNET is also widely used - especially by European manufacturers. RS485 protocol does have driver limits, but as mentioned before these limits can be raised by using repeaters and high-impedance drivers. Polling is simply one efficient technique to find out who is currently active on the network and who is not. 32 control devices on a basic system is quite enough for most implementations. XpressNET, according to Lenz is able to be expanded in the future.

I'm not defending one system or another. Both systems have their merits; both systems have limitations. Generally those people that promote one system over the other are generally users of the said system.

More info on Loconet here.

More info on XpressNET here.
 

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DT
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Discussion Starter · #6 ·
People generally talk of 32 control devices i.e cab controllers. I am not sure if this included other modules.

Stationary decoders take the DCC signals and translate them into electrical pulses to drive points or signals. Reversing modules just switch the polarity of the DCC signals. I don't think these devices limit the scope of XpressNet.

I have 5 DCC controllers: 3 cab controllers and 2 keyboard controllers for the points. Those that have seen the setup can vouch that it is perhaps overkill and only really is all used when there are two or more people on the layout. I could double the amount of controllers and still be well within the 32 device limit.

I have yet to see any club with 32 or more consecutive controllers all active at once.
 

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DT
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Discussion Starter · #14 ·
QUOTE (Rail-Rider @ 4 Jan 2006, 13:26)As a 'digital newbie', I can't help but latch onto the 'number of devices' limitations.

I hate to admit it, but I am quite confused!
...
<{POST_SNAPBACK}>

Rail-Rider, look at the post above yours.

QUOTE (LisaP4 @ 4 Jan 2006, 13:41)...
Doug, ever seen an Ntrack convention? The Network size they run would be impossible with XpressNet.
<{POST_SNAPBACK}>

Lisa, no I have not. Makemineadouble and Dennis seems to though. But be realistic, this is Hornby producing a product for the British Market. Should it aim it's product at clubs with 50 cab controllers running at once using a system that is expensive in terms of license and is generally seen by most users as American? Or should Hornby use a European system that is open source and that IS expandable. Producing a product that works, is cheap and is expandable.

Remember what I said at the start: QUOTE (myself)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.

Where basic RS485 may have limits, an XpressNet system repeaters or high-impedance drivers overcomes these.
 

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DT
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Firmware updates are manufacturer specific.

How you get them depends on the distribution system each manufacturer has in place.

Most of the time, you would have to send a unit in to a service centre for them to 'flash' the EPROM (Erasable Programmable Read Only Memory) chip where the firmware is stored.

I don't know how Lenz is updated, anyone care to reply?
 

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DT
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Discussion Starter · #19 ·
Yes, if the device is connected to the PC then it's a breeze. Not all DCC systems are connected to a PC and not all model railway owner even have a PC...

Obviously with more and more people getting on-line, it is logical for a manufacturer to offer updates via the Web.

I can't see anything available online for Lenz products.
 
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