Frogs and turnout wiring

Frogs are the 'vee' shaped part of a railway turnout/point where the 'left' rail of one tack and the 'right' rail of another track converge. This presents a challenge for normal two-rail model railway electrical design because the powered rails of every section of track must have opposite electrical polarity. PECO addresses this challenge with three approaches.

Correct turnout/point wiring varies by turnout/point type and whether the layout control is DC or DCC.

Images on this page are reproduced with the kind permission of PECO. Text is adapted from PECO catalogues with kind permission.

Terminology

Turnout/point front: the end of the turnout with one track route.
Turnout/point toe: the end of the turnout with two diverging track routes.
Facing direction: train movement from the turnout/point front toward the toe.
Trailing direction: train movement from the turnout/point toe toward the front.
Stock rails: continuous rails leading from the turnout/point front to the outer rails at the turnout/point toe.
Point rails: hinged rails that direct the route in the facing direction. (In larger scales the point rail is a flexible extension of the intermediate rails.)
Intermediate rails: fixed rails between the point rail hinges and frog.
Live route: selected and correctly powered route.

'Electrofrog' turnouts/points

Characteristics

Electrofrogs (also known as live frogs) are made of the same metal as rails and are electrically connected to both point rails.
Frogs are provided with an independent dropper wire for connection to a switched-polarity power supply.
There is no power-routing provision.
Both frog rails on the non-selected route will have the same polarity.

Conductive Electrofrog

Electrofrog electrical continuity. Red and blue represent opposing polarities; purple represents isolated rails that must be powered with switched polarity.

Advantages:

The frog causes no gaps in track power.
The lack of power-routing means that no DCC locomotive is disabled.

Disadvantages:

Electrofrog and point rails require an independent power connection polarity-switched according to selected route.
Installation is more complex than with Insulfrogs.
Both rails on the non-selected route have the same polarity.
Locomotives will short-circuit if they enter the turnout/point against the route selection from the trailing direciton. DCC controllers will stall.

Installation:

Electrofrog 'Method A' conductivity. Red and blue represent opposing polarities. Black and white triangles represent power supply points - either as conductive joiners to adjacent rails or dropper feeds soldered to the stock rails.

Red and blue represent opposing polarities. Black and white triangles represent power supply points - either as conductive joiners to adjacent rails or dropper feeds soldered to the stock rails.

Method A:

Power is provided to the stock rails at the turnout/point front. Power is conducted by the point trail touching the stock rail to the live route.
Insulated joiners are required between the Electrofrog rails and adjacent (inner) track rails but not for the stock rails.

Electrofrog 'Method B' conductivity. Red and blue represent opposing polarities. Black and white triangles represent power supply points - either as conductive joiners to adjacent rails or dropper feeds soldered to the stock rails. Green represents the switched polarity feed via the installed dropper wire to the Electrofrog.

Method B:

Power is provided to the stock rails at the turnout/point front.
Jumper wires within the intermediate rails are cut to insulate the frog from the stock rails.
Correct-polarity power (controlled by an external single-pole-double-throw switch or other device associated with the turnout/point activation) is provided via the frog dropper to the frog.
Insulated joiners are required between the Electrofrog rails and adjacent track rails.

Rail power

Electrofrog track power can be provided by joiners connecting to adjacent rails, except the frog and frog rails which must be electrically isolated and powered by a switched polarity device. Electrofrog turnout frogs extend to and must be electrically isolated from adjacent rails with insulated rail joiners.

Availability

PECO Streamline OO/HO gauge code 75 flat bottom track Electrofrog turnouts:

PECO Streamline OO/HO gauge code 100 flat bottom track Electrofrog turnouts:

PECO Streamline O gauge code 124 bullhead track Electrofrog turnouts:

Installation:

Power can be provided by conductive joiners connecting the stock (outer, continuous) rails, or fed to the stock rails (by soldering power droppers) from below. The point and frog rails which must be powered by a switched polarity device connected to the built-in power dropper wire. Point and frog rails must be electrically isolated from adjacent rails with insulated rail joiners.

'Unifrog' turnouts/points

A combined solution is a convertible hybrid of 'Insulfrog' and 'Electrofrog' solutions. This is further explained in this PECO TV 'Demystifying Unifrog' video.

Unifrog turnouts/points have short conductive frogs that are isolated from even the adjacent part of the frog rails at the toe end. They can be left unpowered, in which case they will perform like Insulfrogs, or powered with a polarity switching system like an Electrofrog.

Characteristics

Unifrog turnouts have an isolated frog that may be powered by a switched polarity device, insulated from the live frog rails.

Conductive isolated Unifrog

Unifrog electrical continuity. Red and blue represent opposing polarities; purple represents isolated frog that must be powered with switched polarity.

Unifrog installation showing switched power supply to frog.

Whereas Electrofrog turnouts must be electrically insulated from adjacent rails, the short Unifrog 'vee' is immediately isolated from the remainder of the turnout/point and each connection to adjoining rails can be conductive.