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Lenz developed USP because it is needed on their systems, both the set 90 & set 100 cut the power to the rails at regular intervals. The USP was developed to prevent any running problems from the loco's having no power or digital signal while the track power is off. They still haven't developed a fix for LED's and lamps blowing from the spikes when the system powers up again.
On other systems USP does provide the advantage of being able to run a loco over several inches of masking tape with it stalling.

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Multitraction, or double heading as some systems call it, is not a standard type of MU or consisting, a system which supports this is quite limited in its capabilities, as Doug says it can only handle 4 loco's in a consist.

There are 3 types of consisting which are accepted as NMRA standrards:-

Basic consisting; this is where any number of loco's are programmed to the same address, all systems support basic consisting. It is however not very practical, as it requires decoders to be reprogrammed before and after running them in a consist.

Universal Consisting; with this method you enter the addresses of the loco's you want in a consist and the command station will remember them, and send commands to all loco's in the consist. The limiting factor here is the max loco's the system can handle, as if the system can handle 10 loco's and you have 9 in the consist only one other loco can be run at the same time.

Advanced Consisting; with this method you enter the addresses of the loco's you want in a consist and the decoders will remember they are in a consist and will respond to the "consist address". There is no limit on the number of loco's you can include in a consist with this method, if you have 10000 loco's you can put them all in a consist, even if your system can only run 10 loco's you can still have a consist of any number of loco's and run 9 others seperately!

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205 Posts
Consist & MU/Multiple Unit are one and the same in DCC talk, basically couple several loco's together and you have a consist/multiple unit.

With speed control knob and dial are one and the same. A pot which is short for potentiometer is what the knob actually turns, this gives an arc of around 270 degrees from stop to full speed.
The better throttles don't use a pot, instead they use a rotary encoder, but still with a knob. A rotary encoder has no physical end to it's travel, and so it can take several rotations from stop to fullspeed, this gives much finer speed control.
My system uses rotary encoders, and I have one loco that takes around 30 sec to move from one sleeper to the next at the slowest speed setting. Control like this isn't possible with a pot.
Some systems use both knobs and buttons to control speed, depending on the system you may be able to use one or the other, or you may be able to use both.

Speed Steps are literally the number of steps between stop and fullspeed, there are 3 modes of speed steps 14, 28, and 128.
14 steps is the original standard and was all we had when DCC first came out, this was later increased to 28 to allow better control, this has now been extended to 128 steps to give the ultimate in fine control.
14 steps is the baseline standard, all systems and decoders must support this to be compatible with each other, 28 & 128 steps is a recomended practice, systems and decoders are not required to support 28 or 128 steps, but is recomended that they do.
By ensuring that all systems and decoders are compatible with 14 steps loco's fitted with an old decoder can be run on any system, while an older system can be used to run loco's with modern decoders.
This is "backwards compatibility," and ensures that all DCC systems can work with all DCC decoders, regardless of make or age.

Functions can be what ever you want them to be, that is the idea of them. Functions can be used to control lights, sound effects, or even mechanical devices such as uncoupling, and doors on carriages.
There are currently 13 functions, F0-F12, however there is a proposal to extend this to 19 functions F0-F18.
The only standard function is F0, this is for forward and reverse headlights, all decoders and systems must support this function. With this function you can turn the headlights on or off by pressing the F0 button on a throttle, also whether the forward or reverse headlight is lit is determined by the direction the loco is travelling in, even when the loco is stopped the lights will remain lit depending on which direction the loco is set to.
Functions F1-F12 are recomended practices for systems, they don't have to support these functions, but it is recomended that they do. Some systems support all of these functions, others only a few of them, while some basic sets only support the standard F0.
What you do with functions is entirely up to you, for some loco's you might not want any functions, just speed and direction, or you may want some special effects to make your model more realistic. You can also buy function only decoders, these don't have controls for a motor, and so are mostly used in carriages and wagons for lighting, opening doors and such.

Some possible uses for functions are
1. individually controlled marker lamps
2. uncoupling
3. sound effects such as whistle/horn, couplings clanking, brake squeal, etc.
4. opening doors on carriages or multiple units
5. smoke units
6. working fans
7. anything else you'd like to add to you models

Also sound decoders which fit inside a loco use these functions to control specific sounds, as well as the chuffing or motor noise which is synchronised to the loco's speed, and because power is supplied even when the loco isn't moving you can activate these sounds at any time, such as sounding the whistle before departing from a station.

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205 Posts
OK I'll start with software upgrade, generally the system manufacturer will provide a chip which replaces the one currently in the command station. Fitting the new chip can either be done by the user, or by a dealer/service agent. The new chip is already programmed with the new software, so you just unplug the old chip, plug in the new one, and go back to running trains.

Stationary Decoders

There are 2 types of decoder;
1. Mobile decoders, these are the ones fitted in a loco.
2. Stationary decoders, these are generally fitted under the baseboard and are used to operate points, signals, or other effects such as level crossing gates and lights or any other device you want to control from your throttle.


Feedback allows devices such as a stationary decoder to report back to the command station, this infomation can then be displayed on throttles or a computer screen.
For instance a stationary decoder might report back which route a point is set to.
Feedback is also used for block detectors, a block detector can sense when a loco enters it's section of track, using feedback it can then tell the command station that a train has entered it's block.
Used simply like this feedback allows the operator to see what is happening on a layout without actually looking at the layout! For instance you could change a point which is hidden in a tunnel or at the other end of the layout, and you can be certain that it has changed because it has told you so.
However feedback can also be used to affect other devices on a layout automaticaly, some examples are;
1. When a loco enters a block the block detector can tell a signal that it needs to change to red, or it could tell the level crossing lights to flash or the gates to close.
2. When a point is set to the right hand track it can tell the signals to show a red aspect for the left hand track.
3. You could use a block detector to sense when a loco is passing through a set of points, it can then tell the points not to change while the loco is passing through them.
4. Anything else you can think of.

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205 Posts
CV is short for Configuration Variable, decoders have over a thousand CV's which define how it is configured, or rather how it responds to a command given from the throttle, and can all be altered by the user to alter the performance of each decoder, and therefore each loco.
Most of these CV's the user will never need to change, some they will, some can be adjucted if you wish. I'd put CV's into 4 categories, of which only the first category must be changed, the rest can be done if you want to change how your loco runs:-
1. Identity CV's, these determine the loco's address, and therefore must be differant in each loco. All decoders are supplied by the manufacturer set to address 3, this can be changed on all systems, and usually quite easily.
2. Running CV's, these determine how the loco runs, adjustments such as maximum speed, starting voltage, and mid point voltage can be set with these CV's. As an example a tank loco could be set to have a low top speed so it is more contollable at shunting, while a loco that needs a lot of power to get started could have it's start voltage increased so that it starts as soon as the throttle knob is turned. You can also set up acceleration and deceleration rates so that a slowly speeds up or slows down.
3. Function CV's, these allow you to adjust how a function performs, for instance you might want a light to flash when you press a certain function button on your throttle, you can do that with these CV's.
4. Hidden CV's, these are simply CV's that will you will probably never need or want to adjust, or they could be inactive in certain decoders, or even read only CV's such as the manufacturer ID which all decoders have set in CV08.

So what is CV Readback? Well quite simply it means a system can not only set a CV value, it can also read what that CV is already set to in a decoder when the system is in programming mode.

Loco number readback is similar, except it means a system can read a decoders CV settings while the loco is running, not just while programming. This is becoming more widely known as Bi-Directional Communication, in other words the system is talking to the decoder and the decoder is talking to the system.

Auto Shuffle Train/Signal Speed Control, is wher a system can tell a train what to do automatically, without any input from the user. For instance if a signal is red, the system might tell any loco approaching that signal to slow down and stop, then when the signal turns green the system will tell that loco to gradually accelerate till it reaches it's original speed setting. Or it could tell a train that has reached the end of a branchline to stop, wait a few minutes then accelerate back in the opposite direction.
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