ElectroFrog is Peco's term for a Live (powered) Frog
turnout, what some people call power-routing. With most live-frog
turnouts, there are three issues you need to be aware of in order to use
flange clearance between the stock rail and open point
and frog rail changing polarity
vibration causing power/signal problem
Most so called DCC friendly turnouts address issue 1.
Some point out issue 2 and how to cope with it. Most do not even mention
ElectroFrog turnouts can be used right out of the box with no concern
about issues 1) and 3). Only the occasional special need will require
some modification. And even then, the modification will be easy because
of the way Peco ElectroFrog turnouts are made. Issue #2 is the only
issue to be concerned about with Peco ElectroFrog turnouts (and all
live-frog turnouts). Peco InsulFrog turnouts don't even have that issue
to be concerned about. All of these will be discussed below.
Wheel flange clearance between the stock rail and open point
routing turnouts, both points usually carry the same polarity.
Illustration 1 shows how the power flows on a normal power routing
turnout. Polarity is shown with Red and Green lines drawn over the
You can see that the open point has the opposite
polarity. If the clearance between the stock rail and open point is not
enough to allow the wheel flange to go through without touching the
point, you will have a short circuit. But you can see with the Peco
turnout above that there is plenty of clearance even for the fattest
Some manufacturers design their turnouts with this
clearance so close that a short circuit is all but unavoidable (thus
requiring modification to the turnout to make it work properly with
Note: These short circuits generally don't matter when
operating with DC analog because the typical power pack doesn't put out
enough current to harm anything (they generally put out only enough
power to run one train). When a short circuit happens, the power pack
simply puts out all the power it can for the short period of time the
short circuit is occurring, and no harm is done. But with DCC having
enough current on the rails to run ALL the trains, a short circuit can
cause harm. Therefore, Short-Circuit Protection is built into boosters.
When a short circuit occurs, the booster shuts down and the trains stop.
Frog and frog rail changing polarity
Some people call
this Power Routing, some call it Live Frog. Illustration 1, above, shows
how a power- routing turnout is powered when closed for the through
route. Illustration 2 shows how it is powered when thrown for the
You can see that all the track pieces in the middle
changed from green to red. With Peco InsulFrog turnouts, all the track
pieces stay the same regardless of which way the turnout is set.
The reason this is
called power routing is that it can make the route not set for dead. In
the illustration above, you can see that both rails of the through route
have the same polarity. This means a loco can't run (the through route
is dead). With DC analog, people used this to be able to run a loco onto
a siding to let a train pass. But with DCC, this is not needed (simply
because each engineer is controlling their trains independently
regardless of track power).
DCC, it's more important to have good solid track wiring to all rails.
Running power through the point contacts is not as positive as
connecting the siding directly to the track power bus. So to accommodate
a power-routing turnout with DCC, the frog rails must be isolated from
the rails that join to them, as shown in Illustration 3.
Insuring that the frog rails are isolated from the adjoining rail is all
most people ever have to do to use most Peco ElectroFrog products.
However, some ElectroFrog products require a little additional work,
which will be discussed later in this section.
Point vibration causing power/signal problem
DCC, power to the points is far more important than power to the frog.
The typical turnout provides power to the points via slip joints, brass
contacts, or some other method. The problem is, when your loco is
traversing the points, the points vibrate. And with just that little bit
of movement, power is interrupted. It's only for just a nano second, but
just long enough to mess with the signals. Unlike a spot of dirt on the
rail, a whole truck of your loco will be on it. This means that 1/2 of
your power pickup for that side is gone for that nano second. At first
blush, this wouldn't seem too much of a problem, and usually isn't -
after all, you still have as much power in the other truck as locos use
to have. But, with so many more things that DCC does than you could do
before, this kind of power interruption can cause spikes that can be
Peco turnout points get power from two contacts. But
more importantly, these contacts are more positive than on most other
points make contact with the stock rails like all others. But, only
Peco has a spring that forces the points tightly to the stock rails.
Besides providing good solid electrical contact, it also resists
vibration caused from locos running on it.
points also have wipers which make contact to the bottom of the
stock rail. So, with the spring holding the point tightly against
the stock rail, and the wiper making contact to the bottom of the
stock rail, it has two points of contact for power transfer at that
end of the point.
points also have a unique pivot connection to the closure rail. It
doesn't just ride on the pivot pad as points do on some turnouts. It
has two tabs that stick through a hole in the pad, and bend over to
secure it to the pad. This provides contact from the tabs to the
hole in the pad, as well as between the top of the pad and bottom of
the point (again, two (not one) point of contact from that end).
Since this is where the frog and frog rails get their power, it's
important that these pivot points have good contact to provide good
solid power to the frog and frog rails
It's unlikely you'll
need to modify any Peco ElectroFrog turnout. However, if you do, it's
usually very easy. First, the points are secured to a plastic throw bar.
If you need to isolate the points for whatever reason, all you have to
do is make a cut in each of the closure rails, as shown in Illustration
At that point you'll have to feed power to the frog
rails through an independent switch (like many other turnouts require).
Looking at Illustration 5, you can see wire connections between the
closure rails and frog rails.
All you have to do
to feed power to the frog, frog rails, and closure rails on the frog
side of the cuts is to connect a feeder to the wire spot indicated
above. You can't see it in the photo above, but the tie going down from
the feeder connection is hollowed out to accommodate bringing the feeder
out from under the turnout if desired.
ElectroFrog products have frogs that need to be powered irrespective to
a single set of turnout points: 3-Way Turnouts, Crossings, Slips, and
Crossovers (Scissor Crossing). Refer to those pages for information
Again, if using Peco InsulFrog turnouts, none of
these issues are of concern.