PECO Unifrog

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Summary: The PECO UNIFROG is a new turnout design from PECO, combining features of their Insulfrog and Electrofrog products. Out of the package, it behaves like the Insulfrog turnout, but can be wired as an Electrofrog. PECO plans to replace their Electrofrog and Insulfrog products with the Unifrog over time. A limited selection of Unifrog turnouts are available, and the line is expanding with time.


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Many thanks to PECO for providing technical assistance for this article.

PECO Unifrog Announcement

From PECO:

The wiring of these new turnouts is a development of both the Insulfrog and Electrofrog designs.
For current users of the Electrofrog or Insulfrog versions of our turnouts the new Unifrog gives modellers the best of both worlds. As supplied, the turnout is wired completely “live”, except for the frog tip and wing rails, and can be used straight out of the packet without any further modification (and so behaves like an Insulfrog).
The stock rails are wired to the closure rails at the factory, which in turn are connected to the corresponding point rail. This means the turnout is completely live (except for the tip of the frog), no extra wiring required. If the turnout is being used as a switch to isolate a section of track then it is simple job to remove the wire that joins the closure rail and stock rail and it will work like a current Insulfrog. Peco provides a pair of pigtails to allow wiring the turnout to behave like an Electrofrog. (They have been spot welded onto the appropriate places.)
To change frog polarity[1] the PL-13 or PL-15 change-over switch/microswitch, or the SmartSwitch SmartFrog PLS-130 with do the task. A Frog Juicer or a mechanical switch would also work.


PECO Turnouts

PECO manufactures a number of turnouts in various scales.

What is Unifrog?

With Electrofrog and Insulfrog, modellers were able to make good looking functional trackwork. The decision of Electro or Insulfrog had to be made at the time of purchase. After purchase, how you wire the Unifrog is up to you.

Unifrog Description

For ease of identification, the PECO part number has a U indicating Unifrog in the part number on the packaging. Example: ST-U750 is a Unifrog RH turnout, O Scale.

As shown in the picture above, the Unifrog has a metal frog, like the Electrofrog. The difference is that the Unifrog is constructed with gaps filled with plastic at the toe and heel, to isolate it from the rest of the turnout. Out of the package it will operate as a Insulfrog, except it is not power routing. Closer examination reveals the toe and heel of the frog are isolated from the track, so it will be dead when installed. There is a wire welded to the underside of the frog connecting the wing and point rails, allowing it to be powered using a microswitch or another device. This will allow the phase of the frog to be controlled with relation to the switch points, like the Electrofrog. As the frog is completely isolated from the trackwork, no additional gaps or insulated rail joiners will be required on the point rails. Gaps have already been incorporated into the design of the Unifrog.

If you flip the Unifrog over, you will see that there are wires connecting the closure rails to the appropriate stock rail, eliminating the potential of a short should a wheel bridge the gap between the switch and stock rails. Perfect for DCC operations. This also eliminates a failure point, as a mechanical connection using the switch rails isn't needed for power, like the Insulfrog.

The point rails are also connected to their matching stock rails by wires under the frog, like the Insulfrog. Unlike the Insulfrog, the position of the switch rails does not control power routing to the point rails.

Advantages of the Unifrog Design

  1. Ready for DCC out of the package
  2. No mechanical connections needed between switch and stock rails
  3. Dead or Live Frog operation
  4. Switch rails do not change phase depending on the frog's state
    1. Switch rails are not self-isolating. Both routes out of the turnout are powered, regardless of frog mode in use or position of the switch rails.
  5. The point rails are powered via wires beneath the turnout connecting the stock, closure and point rails.
  6. Insulated rail joiners not required on the point rails to prevent a short caused by power routing
    1. This feature is built into the Unifrog construction
  7. The frog is unpowered, unless wired via a switch (to control phase).
    1. Can be converted to Live or Dead frog without removal, by simply connecting or disconnecting the wire feeding the frog
  8. Only the stock rails need to be connected to the power bus

Disadvantages of the Unifrog Design

  1. The frog is dead unless powered
  2. No power routing as in the Insulfrog, should you want to run analog (DC), as the point rails are electrically connected to the stock rails

To reduce the instances of short circuits occurring when operating rolling stock from various manufacturers through PECO Streamline HO Code 83 #6 Unifrog turnouts SL-U8361 and SL-U8362, PECO has made a further modification to the frog, making the frog tip longer, resulting in the two opposed, and live, point rails being further apart. A true rail wheel should have a tapered profile but there are many instances when the wheel profiles are in fact flat, which in some instances is enough to bridge the gap between rails through the frog area. Hopefully our modification will help address the problems caused by these inconsistences and allow modelers to enjoy their hobby a little bit more without having to endure those frustrating short circuits! It is worth noting that all PECO Streamline HO Code 70 and Code 83 track and turnouts are designed to NMRA standards. (Peco, January 2022)

What is the Difference between Unifrog and Previous PECO Turnouts?

The revolutionary aspect of the Unifrog is that you can change your mind. Install them in them as they come (a dead frog as in the Insulfrog), then later convert to a live frog (Electrofrog). With the Unifrog this can be done without having to buy new turnouts. In fact, you do not even have to lift the track to re-wire the turnout, providing a hole was drilled into the benchwork for the frog wire to pass through.

Unifrog Availability

Upcoming UNIFROG Releases
HO 83 #8 Right
#8 Left
N 55 SL–U395F Medium-Radius Turnout – RH
SL–U396F Medium-Radius Turnout – LH
00/H0 75 SL-U1188 Right /SL-U1189 Left Bullhead Large Radius
H0 83 SL-U8363 #6 Double Slip, North American
SL–U8364 Streamline Diamond Crossing
SL-U8364 #6 Diamond, North American
SL-U8361 #6 RH North American
SL-U8362 #6 LH North American
70 SL-U7061 #6 RH North American
SL-U7062 #6 LH North American
SL-U7081 #8 RH
SL U7082 #8 LH
H0n3 70 SL–1552 Code 70 Turnout - Streamline LH
SL–1551 Code 70 Turnout - Streamline RH
TT 55 SL-U1295 Medium-Radius Turnout with Wood Ties – RH
SL–U1296 Medium-Radius Turnout with Wood Ties – LH
0 200 ST–U750 Setrack RH
ST–U751 Setrack LH

Currently the PECO Unifrog turnouts are limited in selection. As tooling is replaced, more Unifrog turnouts will come on the market.

Wiring the PECO Unifrog

There are two options:

  1. Install it directly from the package. The frog remains insulated from the closure and point rails and requires no extra wiring
  2. Use the pre-attached wire to connect the stock rails to the frog using an electrical switch

Unifrog: Wiring for Digital Command Control

Wiring the PECO Unifrog for Digital Command Control is not much different than wiring any other turnout

  1. Connect the appropriate stock rail to the appropriate wire on your power bus
  2. Power Routing of the Frog:
    1. Attach the supplied wire to a Frog Juicer, toggle switch, Tortoise motor or other device with can switch connections to the power bus
    2. If you don't plan on doing that right away, but may in the future, attaching a short length of wire to the pigtail provided may make life easier later
  3. Optional: For reliability, connecting the switch and closure rails with a small jumper (Competency at soldering is a must here)

Power Routing

The PECO Unifrog is not power routing.

From the factory, the point and closure rails are wired accordingly for proper operation. The switch rails are also powered, eliminating the need for a mechanical connection to power them. Closure rails are wired to the adjacent stock rails. The frog is isolated from the closure and point rails. Therefore, insulated rail joiners are not required on the point rails.

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See Also


Demystifying the Unifrog

PECO Plans to gradually introduce Unifrog to all of its ranges of turnouts, in this video we explain what Unifrog is and what its benefits are.

PECO Turnouts Overview

Code 83

A close look at the newly tooled number 6 code 83 Line Unifrog turnouts.

Code 70

The newly tooled number 6 Code 70 Line Unifrog turnouts have been released.

Complementing the PECO Streamline HO "83 Line" track system, the new and expanding "70 Line" system will be perfect for representing lightly-laid routes, short lines, freight yards, industrial spurs and also for modelling the early period of railroads. You might wish to use both systems side-by-side, for example, when replicating a heavily used modern mainline with a secondary route diverging away, or a feed to an industrial spur. To help modellers use both systems in this way we have also released the SL-115 PECO Streamline Transition Track, enabling the connection of our Code 83 and Code 70 systems with complete ease!

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  1. Correct DCC Terminology is Phase