PECO Electrofrog

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Main article: Turnout

Part of a series on turnouts (track switches) and Digital Command Control Named parts of a Turnout

Digital Command Control: Turnouts - PECO Electrofrog

PECO Turnouts

PECO manufactures a number of turnouts in various scales.

They have several types of turnouts:

  • The Electrofrog, subject of this article
  • Insulfrog,
  • Unifrog, a new product which is intended to replace the Insulfrog and Electrofrog products. These products will be gradually phased out and replaced by the Unifrog line.

Differences between PECO's Electrofrog and Insulfrog Turnouts

The electrical power routing of the Peco Electrofrog is different than that of the PECO Insulfrog.


The Electrofrog is a well designed turnout. With the exception of the guard rails, there is no plastic for wheels to run on. The positive locking action of the switch points makes it the ideal turnout for anyone's layout. The main feature is an all metal frog. The Insulfrog may have an all plastic (non-conducting) frog, or a metal one with gaps.

Be aware of the images used to illustrate PECO switches. In many ads the pictures are of Electrofrog types, despite the ad copy saying differently.

With DCC operation, there are a couple of problems. The solutions, however, are simple.

How to Spot the Differences between Electro and Insulfrog Turnouts


  1. Frog may be cast entirely in plastic;
  2. Closure and wing rails are solid;
  3. Plastic filled gap where closure rails meet the frog;
  4. Beginning of frog itself is plastic;
  5. Switch rails are electrically connected;
  6. Power Routing: Closure rails are electrically connected to the appropriate point rails.


  1. Closure rails are gapped before the frog.
  2. Jumper wires underneath bridge those gaps
  3. Frog, closure rails and switch assembly are electrically a unit.
  4. Closure rails are not electrically connected as a pair.

Power-Routing In An Unmodified Peco Electrofrog

The Peco Electrofrog switch was designed in the days of analog operation with the ability to power sidings depending on which way the switch rails were aligned. Drive a locomotive into the siding and then set the turnout for the mainline route. We could rest assured that the locomotive wouldn't creep away on us - assuming there were no additional track power feeds to the siding. The turnout would function as an electrical switch in addition to its duty as a track switch.

We could then flick the switch rails on another turnout which held another locomotive on that siding, then operate that new locomotive. This ability had everything to do with how the Electrofrog was wired - By a combination of the rails and wire bonds on the underside, the switch rails acted as an electrical switch that routed power to either the mainline or diverging route.

While it was not obvious, if the switch was set for the mainline route, a whole lot more than just the mainline route was electrified. In the bottom half of the photo below, we've traced the electrical polarity in blue and red. Take a look at the red rails. Hard to believe that all of these rails, particularly the switch and both point rails are also powered when the switch is set for the mainline route!

Digital Command Control eliminated the requirement for power-routing switches. Locomotives only moved when told to move (via the throttle). When parked, they stayed parked, even though there was still power on all the rails. We also added all kinds of track feeds because we didn't have to worry about power-routing to sidings, particularly around turnouts.

Good DCC wiring practice requires track feeds before and after a turnout. Which caused problems with the Peco Electrofrogs. Because the switch routed the power, depending on how things were wired, Electrofrogs shorted the DCC power bus.

Shorting In the Electrofrog

Making the Electrofrog DCC Friendly

These modifications are recommended by PECO, and illustrated in their data sheet. See the links at the end of this page for links to various PECO documents.

The Electrofrog does not require modification for use with Digital Command Control as found in the package. The modifications listed help improve reliability over time.

Insulated Rail Joiners After The Frog - Mandatory

In addition to adding track feeds before the turnout and after the frog on both the mainline and diverging point rails, the first step is insulated rail joiners on the point rails (inside mainline rail and the inside diverging rail). If your turnouts are already installed, cutting gaps in the point rails after the frog and fill those gaps with epoxy or styrene, to prevent the gaps from closing later.

When you set the switch for the mainline route, the switch rails of an Electrofrog continue to power-route as before. However, because the addition of an insulated rail joiner on the point (inside diverging) rail, we no longer have a short, notwithstanding that both point rails, the straight closure rail and curved closure rail have the same red polarity.


When you set the switch for the diverging route, the switch rails of the Electrofrog continue to power-route to the diverging route. And, because we've added an insulated rail joiner to the (inside mainline) point rail, we no longer have a short, notwithstanding that both switch rails, the straight and curved closure rails have the same red polarity. As a minimum, if you are using Peco Electrofrogs, you must install insulated rail joiners on the point rails. Or gap these rails and fill the gaps with epoxy or styrene. NO EXCEPTIONS!

We still have the problem, where the wheels of our locomotives may create a short between the stock and switch rails. This is especially true for steam locomotives and 6-axle diesels. This wasn't an issue with Analog operation, but DCC is very sensitive to even the shortest time period when an issue like this occurs. One solution is to check the wheel gauge of all your motive power and rolling stock, making corrections as needed.

Wheels shorting between switch and stock rails

Taking a look at the above illustrations, the red switch rail shorts to the mainline stock (blue) rail as the locomotive goes through and its wheels span the gap between the two. OR, the blue switch rail shorts to the red stock rail as the loco goes through. If you still don't see how this happens, take a look at the graphic below. (The nomenclature in the illustrations is incorrect: Point rails are at the heel of the frog.)

As part of the process, verify the wheels and rails are in gauge with an NMRA gauge.

This is what makes a turnout incompatible with DCC.

Peco Electrofrog - Modifications for DCC

So far, you've taken care of Step 1: Adding insulated rail joiners to the point rails beyond the frog. This gets rid of the "built-in" short. We may still have an intermittent short as our locomotives go through the switch between the switch and stock rails. To get rid of this short, we're going to disable some of the circuitry (NOT the rails) and make modifications to the wiring.

This will be done in 3 extra steps and will all be done on the underside of the Peco Electrofrog.

  1. Cut the wire bonds between the frog and the point rails. This disconnects all power to the frog. Depending on which way the turnout is thrown, it also cuts power to one of the point rails.
  2. Solder some wire bonds between the stock and its related point rail. This restores power (with the correct phase relationships) to the point rails.
  3. Add a Tam Valley Frog Juicer (or a switch) to power the frog. This restores power to the frog and sets up a control mechanism which gives the correct polarity to the frog as a train goes through the turnout.

Let's take a look at the underside of the Peco Insufrog.

Cutting The Wire Bonds on the Peco Electrofrog

Solder Wire Bonds Onto The Closure and Stock Rails

  1. Strip about 2" of insulation off a track feed wire
  2. Flux and tin the track feed wire
  3. Flux and tin the undersides of the rails shown in the photo below
  4. Solder the tinned track feed wire between the closure and stock rails
  5. Cut the excess wire off.
  6. Repeat for the other pair of rails

Correct Phasing for the Frog

  1. Strip about 1/2" of insulation off one end of a 12"-18" piece of track feed wire.
  2. Wrap the feed wire around the wire from the Electrofrog close to the base of the turnout.
  3. Add flux and solder the wires. (Cut the excess wire from the frog.)

See Also

External Links

PECO Technical Page

There are a number of data sheets, in various languages, available on the PECO Technical Page. This link goes to the English Code 83 Electrofrog turnout. OO/HO Gauge Electrofrog Turnouts/Crossings (Code 83)