One feed, nine metres
The defining electrical property of a T-TRAK layout is that it doesn't really need wiring. Every module joins to the next through the Kato Unijoiners, and those joints conduct power as well as align the rails. The current pulled by an N-scale loco — typically a few hundred milliamps at most — passes happily across many joints in series before voltage drop becomes detectable.
For analogue DC operation a single feeder module is sufficient to supply roughly 9 m of layout end-to-end without measurable resistance loss. Most domestic and small-club layouts never exceed that figure, so a single feed remains the norm.
For DCC, the same 9 m figure is best treated as a starting point rather than a hard limit. Long layouts, or layouts with many sound-equipped locos drawing simultaneously, may benefit from a second feed introduced at the far side of the loop. The decision is judged at the layout, not specified in the standard.
The feed module itself is unremarkable: a single Kato feeder track — #20-041 for N or #2-151 for HO — set into a standard module box, with its supplied blue/white pigtail brought out to a connector mounted on the underside or end face. There is no special transformer, no dedicated booster, no in-module electronics. The module is a junction, nothing more.
Polarity, simply
Every Kato feeder track ships with a two-conductor pigtail: one wire blue, one white. The convention agreed across Australian T-TRAK is direct and easy to memorise:
BLUE → outer rails. The blue conductor of every Kato feeder lands on whichever rail sits on the outside of the layout — that is, the front rail of the front main and the back rail of the back main. The white conductor takes the inner rails. If every module follows the rule, every module joins to every other module without thought and without sparks.
The reason it works is the symmetry of a T-TRAK loop. Modules are flipped end-for-end as they go around the layout, but the "outer" rail of the layout is still the outer rail no matter which way the module faces. Anchoring polarity to that geometric fact rather than to any one wire colour at the panel makes the rule survive every rotation.
Connector standard
Australia standardises on RCA twin sockets at every module that brings power out. White is the front track; red is the back. The two sockets sit at least 100 mm from the module end — far enough that adjacent modules' connectors don't crowd each other — and approximately 35 mm apart from one another so that twin RCA plugs separate cleanly.
Orientation matters. With the module facing you in its operating position, the white socket sits on the LEFT and the red on the RIGHT. The inner pin of every socket carries the inner rail; the outer skirt carries the outer rail and is therefore the wire that runs blue from the feeder.
Because RCA is asymmetric in colour but symmetric in shape, the colour coding does the talking. A pair of properly wired modules joined by RCA cables can be reversed at either end without consequence — what matters is that white only ever meets white and red only ever meets red.
Anderson PowerPole
PowerPole is the recognised alternative connector. It is more popular among club layouts than home layouts because of its locking action — pulled cables pop apart cleanly without tearing — and because the same housings used at 15 A work just as well at the modest currents an N-scale layout actually draws.
The key rule for visiting a meet: if you wire your home layout in PowerPole, you must bring an in-line PowerPole-to-RCA adaptor cable, presented in standard polarity, and notify the meet coordinator in advance. The venue is wired in RCA. Your booster is wired in PowerPole. The adaptor is your responsibility.
Housing colours match the wire colours used by Kato: blue housings to the outer rails and white housings to the inner rails. (The red used at the RCA panel is a colour-code on the socket; the bus side of the same circuit still carries a Kato-blue conductor.)
For modules that mount PowerPoles flush to a face, 3D-printed mounts are widely shared. The accepted dimensions for a single-pair PowerPole face plate are: outer diameter ⌀ 36 mm, hole ⌀ 26 mm, plate thickness 3 mm, and rebate depth that fits up to 12 mm board thickness.
DC, DCC, or both
The standard is power-supply-agnostic. Both analogue DC and digital DCC are supported and either can be used as the venue's running mode. The only mandatory electrical property of the layout is the polarity convention above — anything compatible with that convention is welcome.
If a layout chooses to mix DC and DCC on the same physical loops, the front and back tracks must remain electrically isolated from each other end-to-end. (In fact the standard requires this isolation regardless of supply type, because a turnout placed at a module join could otherwise short the two mains together through the running rails.) The accepted summary is that DCC is preferred on the back track when running mixed: most operators put their visiting locos on the back, and DCC tolerates more decoders running in parallel than a single DC throttle does.
The official document explicitly leaves several DCC details unspecified. There is no recommended command station, no published booster specification, and no current or voltage standard. The only constants are the connector and polarity rules — everything past the panel is left to the layout owner.
For visitors this means: ask the host. The DCC system in use, the configured track voltage, and any short-circuit response time are properties of the booster on the day, not of the standard.
Quick reference
| Wire colour rule | BLUE → outer | universal, every module |
|---|---|---|
| Front track socket | WHITE RCA | left when facing module |
| Back track socket | RED RCA | right when facing module |
| Inner pin | inner rail | white wire from feeder |
| Outer skirt | outer rail | blue wire from feeder |
| Feed cadence DC | ≥ 1 / 9 m | single feed serves up to ~9 m |
| Feed port height — N | 45 / 78 mm | top edge / centre, from front face |
| Feed port height — HO | 96 / 156 mm | top edge / centre, from front face |
| Feed port diameter | ⌀ 19 mm | drilled clear hole |
| RCA min from module end | ≥ 100 mm | avoid neighbour clash |
| RCA twin spacing | ≈ 35 mm | centre-to-centre, white left of red |
| PowerPole mount face | ⌀ 36 / 26 / 12 mm | OD / hole / max board thickness |
| Reference connector | Tamiya Mini | listed in the standard but expensive and increasingly rare |
Isolation kit
For a siding that needs to be switched live or dead independently of the main: fit a Kato #24-830 connector switch where the siding meets the main, an #24-816 insulated UniJoiner at the same point, and a feeder track inside the isolated section. The switch breaks one rail; the insulated joiner breaks the second. The Peco equivalent is any SPST switch wired in line with one rail.
For a passing loop or any section that needs to be selected between two power districts: fit insulated UniJoiners on both rails at both ends of the section, and route the section's feeders through a Kato #24-831 selector. The Peco equivalent is a DPDT switch wired centre-off-on in the same place.
In every case the principle is the same: break both rails of the isolated section, then re-feed it through a switch you control. If the rail is left connected to the main bus through even one Unijoiner the isolation is incomplete.
At a meet
Whatever you wire at home, present standard polarity in-line RCA sockets — white for front, red for back — at the venue. If your home layout uses PowerPole, XT60, screw terminals, or anything else, terminate that with an adaptor cable so the modules you bring expose RCA in the conventional positions.
If you cannot, notify the coordinator before turning up. They may have a spare adaptor, or a position on the layout where your module's local convention will not conflict with anything else. What they cannot do is rewire the venue around an unannounced connector.
Bus wiring · VNSC v0.3
The Victorian N Scale Collective bus convention, currently at revision v0.3, is the most-cited Australian bus standard for layouts that opt to run a bus rather than rely on Unijoiner conduction alone. It is a daisy-chained Anderson PowerPole bus run beneath the modules, with RCA fan-outs at each module's feed point.
The bus assignment by colour:
| Front track bus | black + white | power to front main |
|---|---|---|
| Rear track bus | black + red | power to back main |
| Third track bus | black + blue | optional third running line |
| Auxiliary bus | black + yellow | accessories / aux power |
The four-pair scheme covers a layout that can have up to three running lines plus a separate accessory feed. Smaller layouts use only the front and rear pairs and ignore the rest.
Tongue top, black left, red/indicator to RCA centre.
Stack the PowerPole housings with the locking tongue pointing up. With the connector face toward you, the black (common) pole sits on the left and the indicator-coloured pole sits on the right. Where the bus crosses to an RCA dropper, the coloured pole goes to the RCA centre pin and the black common goes to the outer skirt.
Held to one rule, every drop along the bus is identical. Held to no rule, every drop is its own argument.
A feeder on the bus may carry between one and four RCA connections per drop, depending on which of the four buses it serves. Bus wire gauge, total run length limits, and termination conventions are not specified in the published standard — those are left to local installation, sized to the expected current draw of the layout and the number of locos likely to be running simultaneously.
Other clubs run their own bus conventions. The Ipswich Heritage Model Railroad Club (IHMRC) maintains a parallel bus convention for which the written specification is currently noted as "to be advised" in the latest revision. Published photographs of IHMRC layouts show black-sheathed twin lead with blue and red PowerPole housings at the junctions, broadly consistent with the VNSC colour scheme but without a publicly-binding written rule. If you are joining an IHMRC meet, ask the coordinator for the local practice on the day.