Controls & electrical

Choosing the right type of turnout

All-live or power-routing: the best type of turnout depends on how you want to run your model railroad
By by Andy Sperandeo
The track switch or turnout puts trains on new tracks or can shunt cars into yard sidings. But there's also electricity going down those rails, and depending on the style of turnout you use, you can cause a short circuit if you don't wire it correctly.

The wiring principles aren't hard to understand, but they're not always obvious by just looking at the track. So here are some basics, starting with what kind of turnout to use.

Is it all-live or power-routing?
The two rails of model railroad track must be kept insulated from each other to prevent short circuits. For ordinary track this is accomplished by using plastic, wood, or some other insulating material for the ties. At turnouts and crossings, however, the rails have to cross each other, and something more has to be done to maintain insulation. The set of measures we take to avoid short circuits in trackwork is known as two-rail wiring. Two-rail wiring is easy enough, but you have the choice of doing it your self or having it done for you. It all depends on the kinds of turnouts you choose. There are two types-all-live and power-routing.

All-live turnouts have insulated frogs, jumper connections around the frogs between the corresponding closure and frog rails, and, jumpers between corresponding closure and stock rails. The points are separately attached to insulated throw bars. All this keeps the two rails electrically separate at all points and keeps both routes through the turnout powered-hence the term "all-live." Most sectional track turnouts, including the popular Atlas Snap Switch and Custom Line brands, are all-live types.

Power-routing turnouts are simply all rail with no insulation at the frogs and no jumper connections. The points need not be insulated at the throw bar or the hinges, and in fact they're often joined with metal bridles. Only one route through this kind of turnout can be powered at a time - when both rails under a locomotive are connected to the same potential, the effect is the same as if they were not connected to anything. That's why these are called "power-routing" turnouts, because they switch power as well as trains from one track to another.

Most turnouts sold for use with flexible track are power-routing turnouts. So are most modelers' hand-laid turnouts; it's simpler and easier to build a turnout this way when you're doing it yourself.
All-live turnouts are simpler to wire as long as you're buying them readymade. The combination of insulated frogs and jumpers keeps the rails properly insulated and connected through all sorts of turnout arrangements, and the power-feed wires from the power pack, "feeders," can be connected anywhere.

Power-routing turnouts are another matter. Orienting these turn outs frog-to-frog causes short circuits, as do feeder wires attached on the frog side of a power-routing turnout. To use these turnouts you have to insulate rails in certain places with gaps or plastic rail joiners, and be careful where you attach feeders.
Which one to use?
While the all-live turnout offers ease in wiring, the power-routing turnout gives an advantage in operating.

With power-routing turnouts, you select which track is powered just by lining up the turnout points (throwing the track switch). If a turnout is turned toward a siding, the power goes to that siding and a locomotive can enter it. By orienting the turnout back to the mainline, the power to the siding is cut off and the locomotive must wait while another train passes. To achieve the same operational advantage with all-live turnouts requires even more complicated wiring.

Or at least it used to. With the growing popularity of Digital Command Control , the turnout equation changes. In DCC, ideally all the track is continuously powered as it's used to transport a carrier wave signal to the locomotives. It's the electronics installed in each locomotive that interprets if the signal to speed up, slow down or reverse is meant for that train. With sophisticated sound and lighting systems, an all-live turnout allows a locomotive to sit on a siding and still receive power to emit steam hisses and keep its lights bright while an express barrels alongside. The engine remains animated even if not moving. With a power-routing turnout, it would just be dead.

So the choice depends on what you plan to do with your layout. If you plan a gradual conversion to DCC, power-routing turnouts would still offer an advantage for controlling locomotives that have not yet been converted. But if you're just starting out with few locomotives and you feel committed to using DCC, all-live turnouts will greatly ease your wiring efforts in building a layout.

Adapted from Easy Model Railroad Wiring by Andy Sperandeo, published by Kalmbach Books.
Why not just call a turnout a switch?
Ask someone on a real railroad about a turnout, and he'll yell at you to get out of the yard before you get run over by a train. But even if you weren't trespassing, the person you asked might not know what you're talking about. A switch is what a railroad worker throws to put a train on a different track.

In model railroading, however, the convention is to call track switches turnouts to avoid confusion with the many electrical switches model railroaders also have on their layouts.

So just to make sure it's clear, remember: a track switch is a turnout while an electrical switch is a turn on.