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chriswright03

What size wire to use?

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Just getting on with the boards for my O gauge layout at long last. As stated above I have the Powercab with the 3 amp booster and it is only a short layout so will only have one loco running at a time even if others with sound are active. So I just want to know what size wire is best to use. Having looked at sites like Wiring for DCC and others they all seem to mention the size in some form that means nothing at all to me.

 

I am thinking of using 13amp household blue and brown wire for the bus and then maybe the same for droppers or could I get away with smaller? I do have some 7/0 2mm Gaugemasters wire but it looks a little thin for the current although it is often used in OO layouts.

 

Any help appreciated.

 

Chris

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Hi Chris, long time......

I would suggest for the bus wire using 14 gauge wire and for the droppers 18 gauge providing you put them at all the rail joints.

Hope this helps.

 

Colin

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Colin,

 

No it doesn't help at all really. Sorry but that is my point that I do not have a clue what 14 or 18 gauge is or what I could compare it to. Of course 13amp household wire will mean about the same to you in Florida I would think.laugh.gif

 

Chris

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<Snip> So I just want to know what size wire is best to use. Having looked at sites like Wiring for DCC and others they all seem to mention the size in some form that means nothing at all to me.

 

I am thinking of using 13amp household blue and brown wire for the bus and then maybe the same for droppers or could I get away with smaller? I do have some 7/0 2mm Gaugemasters wire but it looks a little thin for the current although it is often used in OO layouts.

 

Any help appreciated.

 

Chris

Hi Chris

Obviously your not visiting the right web site. :O :o

Link to my DCC page Wire sizes are discussed here.

 

My rule of thumb is... For the actual DCC bus always use the largest size of conductor (wire gauge) thats practicable.

 

As for dropper wires, if every section of track is fitted with droppers then 16/0.2mm will be fine. Do try to keep the length of dropper between rail and bus wire as short as possible.

 

Your Gaugemaster 'layout wire' which is 7/0.2mm is too small to use for DCC especially with "O" gauge current demands. Use it for feeding non DCC items like colour light signalling, LED indications back to the mimic panel and feeds to any Stall style point motors (not solenoid ones though).

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Hi Chris, long time......

I would suggest for the bus wire using 14 gauge wire and for the droppers 18 gauge ...

The AWG system is so simple B) ...I wish they'd use it on our side of the Pond... :rolleyes: :angry:

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Just getting on with the boards for my O gauge layout at long last. As stated above I have the Powercab with the 3 amp booster and it is only a short layout so will only have one loco running at a time even if others with sound are active. So I just want to know what size wire is best to use. Having looked at sites like Wiring for DCC and others they all seem to mention the size in some form that means nothing at all to me.

 

I am thinking of using 13amp household blue and brown wire for the bus and then maybe the same for droppers or could I get away with smaller? I do have some 7/0 2mm Gaugemasters wire but it looks a little thin for the current although it is often used in OO layouts.

Rather than choosing according to 'Size', a better approach is to choose by 'Rating'.

The type of insulation used on the wire also has a bearing on this, but for the most part we would be dealing with PVC insulation.

7/0.2 is equivalent to 24AWG, and is normally rated at 1.4A

16/0.2 is equivalent to 20AWG, and is normally rated at 3A

Note that the current values shown at the Wikipedia link are Fusing Currents, i.e. the current at which the copper wire itself would get hot enough to melt and go open circuit . Not recommended for model railway use!

The normal ratings are much lower because they take into account the limitations of the environments for which they are intended.

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I also have an NCE Power Cab with 3A Booster for a small 0 Gauge layout.

It is worth noting that the "booster" is not in addition to the supplied 1.2A plug-in transformer (13A plug type) but instead of and will require a seperate transformer to power it.

If you wanted to section the layout, you could use each unit to supply different areas of the layout, but your total current available using the "booster" is only 3A.

 

The 3A is plenty for my own needs, but before starting any wiring, take time to be sure of your own projected requirements.

 

regards

Stewart

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Yes I am Brian but at the moment I am looking at the pages on how to wire the electrofrog points.blink.gif Just have to decide which point motors to have and would really prefer to have manual throws in lever frames as long as I can change the polarity with them. Didn't get around to looking at the wire on there. Just off to do it now. Thanks to you and everyone else for the help.

 

Chris

 

 

 

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OK Brian I have now had a look at your information about the wire. Have to say I am still confused though. Without going to somewhere like Maplins I do not have a clue what 16/0.2mm looks like. Nor do I understand what AWG actually is other than American wire gauge which doesn't help me associate it with anything that I know I have had a look at Wikipedia as well but it is way too technical for me.

 

Having been told in the thread that 13 amp household wire is OK for the bus I think I will use that because I have enough of it lying around. Quite happy to buy new stuff but if I don't need to I may as well use what I have. So what would be best for the droppers? Can I for example use the thinner lighting wire?

 

Maybe it is just as easy to go into Maplins and buy some. Thing is if the bus wire is rated at 3 amp don't the droppers have to be the same?

 

Sorry if this is more difficult than it should be but I think this is what can put some people off when the mind cannot picture what it is that is being discussed. I can understand what household 13 amp wire is because I see it every day and the same with lighting wire for a table lamp for example. I am off for another trawl now to see if I can make sense of it all.

 

Thanks Chris

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Rather than choosing according to 'Size', a better approach is to choose by 'Rating'.

 

But as I'm sure Gordon is aware, but may not be obvious to others reading this, you can't use a wire with a rating of 3A just because you have a 3A booster. The rating ensures the wire doesn't overheat at maximum current but model railways also have to consider voltage drop and its effect on short circuit protection. If you have too long a run of wire of relatively low rating then the short circuit cutout won't operate when a short circuit happens!

 

It is essential to make sure that the short circuit protection operates reliably with a short circuit anywhere on the layout. This can be done by a simple coin test or by measuring the resistance and checking that the short circuit current will exceed the booster rating and therefore operate the cutout. I suspect the OP will be OK with a small layout and a 3A booster using 13A cable or similar, but it's something other people reading this thread need to know about.

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<sip>

Having been told in the thread that 13 amp household wire is OK for the bus I think I will use that because I have enough of it lying around. Quite happy to buy new stuff but if I don't need to I may as well use what I have. So what would be best for the droppers? Can I for example use the thinner lighting wire?

 

Maybe it is just as easy to go into Maplins and buy some. Thing is if the bus wire is rated at 3 amp don't the droppers have to be the same?

 

<snip>

Thanks Chris

Hi Chris

What exactly is 13 Amp mains cable?

Could it be 1.0mm2 or 1.5mm2 (which is half as large again as the 1.0mm2) Or is it what is used to feed 13Amp power sockets - 2.5mm2 which is in fact capable of handling around 26Amps So not 13 Amp at all?????

 

Unfortunately "13Amp mains cable" is a very poor terminology and is not specific! :( :(

 

You would not use 3.0Amp rated cable for the bus pair of wires. A larger wire size is necessary. If you wish to use solid core mains cable - insulated cores striped out from the outer sheath, then consider as a minimum 1.5mm2 and better is 2.5mm2. But installing these under the layout may in some cases be problem? So some users prefer to obtian the equivalent size in a flexible wire.

 

16/0.2mm flex droppers (Called Equipment wire) are the minimum wire size ideally to use. If you wish to strip out the cores from mains flex for the droppers then 0.5mm2 2 core cable will be fine (As is used in table lights and low current 230volt appliances).

 

You need to ensure the main bus pair of wires are large enough to overcome any volt drop that occurs within their length. Hence the recommendation to use the largest size of conductors practicable.

Droppers mainly conduct the current within the section of rail they feed. So they can be of a smaller wire gauge. :D

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I agree that "13 amp mains cable" is poor terminology but it is also safe to assume whichever cable from the range of options this phrase covers is going to safely handle the current in a 3-5 amp system.

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Hi Chris

 

Apologies, I think I may have misled you by not mentioning (on purpose) cable, the 3 Amp I am talking about is the output available from the booster, not the current rating of any cable to be used.

 

I am very much a novice when it comes to DCC and I only mentioned the booster because when I purchased mine I thought it was in addition to the original supply rather than instead of and I was surprised, and a little annoyed, when I got it home and read the instructions, that I had to purchase another transformer for it.

 

My own train set is wired for DC and DCC so it is fully sectioned (all on for DCC) and I do not have buswires as such, so no one cable is ever asked to supply the layout, being small it is also run with one loco at a time.

I also have completely seperate supplies for layout lighting and point motors so my electrical loads for each function are relatively small.

 

regards

Stewart

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In choosing the 'correct' - perhaps a better word is 'appropriate' wire for a [DCC] powered layout, there are 2 basic considerations to be met:

 

1/ As with 'analogue-cab-control' (1 loco per section, wires direct to each section**) wire of sufficient size as to 'safely' and 'adequately' carry the expected current to the track. This obviously varies with Scale, whether Sound is fitted (and how many Watts), and Lighting for locos and stock.

{** the common return may require a larger wire size, if it is sharing currents for moer than 1 loco}

Allowance should be given for more current in the future - as sound is added to silent layouts, or lighting to 'wartime blackout' layouts - as its easier to 'get it right' originally, than to rewire it all later.

 

The concern in this aspect is the voltage drop / power loss caused by inadequate wiring over long distances: size of layout therefore has a great effect! A Garden layout is likely to have to use larger wires than a table-top layout in the same scale, simply due to the longer cable runs involved.

 

The voltage drop experienced can be measured with a Voltmeter at the distant part, with a heavy-current-consuming loco moving (eg one with sound).

[Caution: for dcc, not all digital meters measure the dcc near-squarewave accurately {Fluke's do} - a bridge rectifier and DC-measurement is an alternative method.. just allow for the diode voltage drops on the rectifier].

 

DCC decoders should all work down to about 8V (some less), but a maximum 'drop' of only about 1-2V at full current is a better choice, allowing a margin for further losses due to dirty rails etc. In DCC, protection for/within a loco is provided by each individual decoder, inside the loco.

 

2/ Safety: Protection from Short-Circuits. Hurricanes may Hardly Ever Happen in Heriford, Hertfordshire or Hampshire, but short-circuits from derailments or wheels momentarilly bridging gaps at points and crossings, WILL frequently happen: enough to be considered a problem to handled.

Some Short Circuits may pass unnoticed (for a while). In this case, the 'maximum possible' current will pass through the wiring, and then, as with determining the rating for 'mains wiring', the heating effect of this continuous current needs to be considered; the wire has resistance, therefore it heats up, and if this is not naturally dissipated, will increase the wire temperature so that the plastic covering may soften and melt and cause further short-circuits, if not causing something nearby to catch fire! [The worst case example from a few years ago being Wire-Wool Trees!!]

 

An analogue dc controller is chosen to have a current rating for a 'single' locomotive (or consist) - it could be from 0.25A to 5A or more according to intended scale. 'Somewhere' above that figure, a safety cutout will operate. Old controllers may have used a bi-metallic strip - and the current this opened at will have depended on the ambient temperature.

[in a physics lab where I taught, I demonstrated that the classroom bench terminals could be shorted in winter, without the trip operating!!]

More modern controllers may have more precise current limits, or thermal fuses [ which can fail if left in sunshine ! ] My point is that although they have protection, it may vary considerably between controllers. The same applies to DCC - amplifier or booster: However, here the NORMAL current value is probably higher, as more than 1 loco can be 'in use' at the same time....and they are more likely to have sound and lighting

Therefore, the 'Short-circuit' or maximum current which can be SUSTAINED WITHOUT TRIPPING is likely to be much higher: 2.5A,3A,5A, or 10A etc

- again according to scale, and intended market. [Bachmann EZ-dcc Trainset conroller and power supply providing less current than a Massoth [email protected] Amps].

 

The wiring needs to ensure that there is a/ no adverse heating effect at this VALID current. Some may conside 'expectation' may be used here, in choosing a lower rating based on eg it being old-analogue wiring 1 per section - as this makes an UNKNOWN short more likely to continue and create a problem - but may remain 'valid' if only a low-current 'starter' dcc controller is used (eg <2.5A, for example); but CAN BE VALID if Electronic cutouts of lower current are used to protect the indiviual sections.

 

The 'Well known' and simple test is to simulate the situation which SHOULD cause a cut-out to operate: by simply placing a coin (or equivalent link)

across the tracks: the cutout should then operate so as to protect the wirng. If this does not happen, then the wiring is too small for the possible fault current which CAN (and WILL) occur !! (An easy pre-wirng test is to use a whole reel and see if shorting it at the far end trips the dcc unit)

 

If this explanation has not provided a 'definitive' answer as to what an unknown layout should use for its wiring; I do not apologise. The reasoning is here for all to follow, and draw you own conclusion for your own circumstances:

 

In my 00/HO dcc layouts I use various sizes of wire - according to size, For LGB dcc I use the same as 00/HO for portable layouts, but multiple multistrand 'high current' speaker flex in the garden. Obviously many buy 'mains' wiring (myself included): but ensure it cannot be confused with 'mains use' - perhaps by removing the outer sleeving, and certainly by not having the same type/colour used for mains near the layout 8-)

Since there need be no 'indivual sections', as per cab-control, with dcc; when multiple connections are made from a BUS wire disitribution, these are in parallel, and therefore effectively larger wires. Perticularly in the garden, where the weather may affect contacts more than indoors, multiple connections helps mask/overcome a failing indivual contact.

In smaller scales, the nickel silver track has higher resistance than in larger scales or Track codes. In LGB, Brass rail (a better conductor) is also used.

 

30 years ago, for Zero-1, I used '30A-Ring-main T+E cable' stripped form its outer sleeve for the track and accessories busses beneath the layout. 'Normal' 1A 'layout wire' was then used for multiple connections (droppers) to the track. The coin test was passed in all locations. I find the single-core cable rather stiff, and inflexible; hence I use Flex (mutistrand wire) in my present layouts: '6A' for busses is adequate, in my experience, for the <10m runs on my 8m x 5m layout. I use (multiple) 15A or more 'loudspeaker' flex for the garden (maximum run 25m) with LGB locos and overall Maximum of 8A. LGB point motors, operated via the track and accessory decoders are NOT solenoids, but half-turn motors (no commutator) - however, they still increase the current taken during operation.

 

With experience from Zero-1 days, I have Rampmeter dcc-current monitoring, and an Iron Core AC Ammeter for 50Hz solenoids/lighting, as well as 'Intelligent PS-X breakers for each of 4 TRACK power districts, (but not on the dcc accessory bus as less risk of a short circuit), all supplied from Roco 3.2A Amplifier/boosters fed, in turn, by regulated Switched-Mode Power Supplies set at 18V or less (16Vdcc on track). At present, my highest continuous current is the 12V bus taking 4A for LED lighting of the layout and electronic modules - and this uses the 15A loudpeaker' wire bus.

 

rgds

phil s

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Therefore, the 'Short-circuit' or maximum current which can be SUSTAINED WITHOUT TRIPPING is likely to be much higher: 2.5A,3A,5A, or 10A etc

The "maximum current which can be SUSTAINED WITHOUT TRIPPING" is just the normal operating limit of the booster.

 

A "short circuit" is a fault and should *always* cause the booster or controller to trip.

 

Andrew Crosland

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Hi Chris

What exactly is 13 Amp mains cable?

Could it be 1.0mm2 or 1.5mm2 (which is half as large again as the 1.0mm2) Or is it what is used to feed 13Amp power sockets - 2.5mm2 which is in fact capable of handling around 26Amps So not 13 Amp at all?????

 

Unfortunately "13Amp mains cable" is a very poor terminology and is not specific! https://www.rmweb.co.uk/community/uploads/emoticons/default_sad.png :(

 

You would not use 3.0Amp rated cable for the bus pair of wires. A larger wire size is necessary. If you wish to use solid core mains cable - insulated cores striped out from the outer sheath, then consider as a minimum 1.5mm2 and better is 2.5mm2. But installing these under the layout may in some cases be problem? So some users prefer to obtian the equivalent size in a flexible wire.

 

16/0.2mm flex droppers (Called Equipment wire) are the minimum wire size ideally to use. If you wish to strip out the cores from mains flex for the droppers then 0.5mm2 2 core cable will be fine (As is used in table lights and low current 230volt appliances).

 

You need to ensure the main bus pair of wires are large enough to overcome any volt drop that occurs within their length. Hence the recommendation to use the largest size of conductors practicable.

Droppers mainly conduct the current within the section of rail they feed. So they can be of a smaller wire gauge. https://www.rmweb.co.uk/community/uploads/emoticons/default_grin.gif

 

 

 

Yes sorry Brian and the rest of you that are kind enough to help me. I now realise that my description leaves a little bit to be desired.angry.gif

 

What I have is 1.0mm multi strand wire that has come out of a 13 amp extension lead that was no longer required. I am assuming this is rated at 13 amps because that is what it is said it was, a 13 amp extension lead. As the layout is only 10' 6" long I don't think their will be much voltage drop in that. It will have sound loco's on it but I would have thought two running (not both moving) would be a maximum at any one time.

 

As regards some of the other replies well I am afraid that whooshing sound is them going over the top of my head.laugh.gif Honestly guys all I wanted was to know what size wire to use for the bus and droppers. As I have said already I have the 3amp booster and of course a transformer to go with it. I have this weird sort of logic that tells me if the wire from the mains to the booster/transformer can handle the power surely that is big enough for the bus and droppers to run the locos. I don't wish to sound ungrateful because I am not but I am becoming more confused than what I was at the start.

 

Thanks again.

 

Chris

 

 

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Hi Chris

Don't worry we all have to start at some stage. :)

If your flexible cable is 1.0mm2 then on the size of layout you have it will be ok, but is really in my view a little on the small size. I would recommend a minimum of 1.5mm2 but then I always build larger than really needed! Mainly because it leads to none or virtually no problems later on.

 

Ensure your dropper wires from the rails to the bus wires are kept as short as practicable and use 16/0.2mm or 0.5mm flexible wires stripped from former 2 core mains wire. As I said previously the type used for table lamps etc.

 

Solder all connections and you'll be fine. :D

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Thanks for that Brian. I can get on with it now as I have plenty of both cable. If it goes bang I will let you know.laugh1.gif

 

Chris

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As regards some of the other replies well I am afraid that whooshing sound is them going over the top of my head.

You & me both, matey!! :blink:

 

I don't wish to sound ungrateful because I am not but I am becoming more confused than what I was at the start.

Again, me too... I'm contemplating getting into DCC myself, but there are times when things do seem to be incredibly complicated... all we want to do is run a few trains..!!! :rolleyes:

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Yes sorry Brian and the rest of you that are kind enough to help me. I now realise that my description leaves a little bit to be desired.https://www.rmweb.co.uk/community/public/style_emoticons/default/angry.gif

 

What I have is 1.0mm multi strand wire that has come out of a 13 amp extension lead that was no longer required. I am assuming this is rated at 13 amps because that is what it is said it was, a 13 amp extension lead. As the layout is only 10' 6" long I don't think their will be much voltage drop in that. It will have sound loco's on it but I would have thought two running (not both moving) would be a maximum at any one time.

 

 

 

Thanks again.

 

Chris

 

Sorry Chris,

I guess I've been over here for so long that I'd forgotten the difference between UK and US wire sizes.

Your best bet for the bus wires would be the solid conductor type of wire found in twin flat cable that is used in houshold wiring.

The 13 amp flexible wire would be perfect for your droppers ( if I remember correctly that should equate very closely to the 16 gauge I mentioned in my last post)

 

Regards

Colin

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I get that whooshing sound too. It happens a bit less now than when I started.

 

I think that everybody that ventures into dcc gets that sound, but, as you said it does get easier......

 

Regards

Colin

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Some practical comments:

 

Blacklade uses an NCE Powercab, with the supplied US 1.2amp transformer operated via an adaptor plug (I had to carve bits of the top projections away so the transformer would fit on - no innards were exposed please note)

 

The main DCC traction buses are made from what was sold in the DIY place as mains cable , containing 2 insulated cables of solid copper about 2mm diameter, and a thrid uninsulated copper wire for the earth , enclosed inside an external plastic insulated sheath . The outer plastic insulation was removed , to extract the two wires meant as live/neutral: these were then used as the 2 bus wires, and sections stripped to the bare metal to allow dropper wires to be soldered on to the solid copper

 

Where possible 16/0.2 wire was used as droppers , eked out in places by 7/0.2 wire . Connections from the NCE panel to the traction bus via the program track switch , and from traction bus to the interboard socket are 24/0.2 wire nominally rated at 5A. I think the wire in the interboard connector is similar - it's 7 core cable with chunky wires. 7/0.2 wire is more or less confined to the 12V DC feeds from the stabliised converters to power signals and lighting, and from decoder outputs to Tortoises . The auxilary 16V AC supply which powers the 12 V converters, the MERG decoder and the Hoffmann motor is 24/0.2 wire. The wires to the frogs off the Tortoise swtiches are 7/0.2mm beige, cos that was all I had. I believe 16/0.2 wire is nominally "3A wire"

 

This may be overkill, but that's better than underdoing it. Some folk may remember an exchange on MREMag a few years back where an anti DCC poster claimed that DCC layouts would go up in flames because of uncontrolled short circuits of 10A current or more - well I was on the other side of that exchange , and as the then leader for a club project, having been given the Health and Safety pep talk to the effect that "you are legally responsible under the Act for all safety", and being well away our usual show venue was twichy about fire , having had 2 fires in 30 years, I tend to want to bombproof the wiring

 

On the club project similar solid copper mains wire was used for the traction buses but droppers were "1 amp layout wire" (I think 7/0.2 but can't be quite certain). On one board where droppers were 3' long or more in places, this resulted in noticeable voltage drop , and the board was subsequently rewired to shorten the droppers as a result. Overheating is only one (less likely) issue. The finer the wire , the higher the resistance at a given current , and the longer the run the greater the resistance... Hence heavier wire helps beat voltage drop. With only 1.2A to play with, I can't afford transmission losses . Similarly , if I ever upgrade to a more powerful DCC system, I want to be sure the layout wiring can handle it easily

 

After the MREMag spat I did have a discussion with someone in the club , which concluded that 1A wire would be ok for droppers because under normal conditions the total current draw would be spread over many locations and many droppers , and no single dropper even with a sound locoi, should exceed 1A current flow . Under short circuit conditions the protection on the command station would trip, and any high current flow would only be momentary and therefore would not overload the wiring (This by the way is the source of my aversion to the "car light bulb trick" - it was suggested by the other party on MREMag that this meant DCC layouts would be subject to short circuit currents of 10A for extended periods as car light bulbs kept the current flowing. That's a good argument against fitting car light bulbs, but a bad one against DCC . Use a circuit breaker. To quote Crosland above

A "short circuit" is a fault and should *always* cause the booster or controller to trip.

)

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