So what you're looking at in this photo is a bottom side corner of my HO DCC (Digital Command Control) industrial shelf switching train layout.
The powered up circuit board is what is called as a "Frog Juicer," used for powering the frog part of the turnouts as seen in the insert photo with the blue arrow pointing at the frog.
The frog made from metal is isolated from the rest of the turnout. The frog is isolated to keep the track power from shorting out when a locomotive powers through the turnout (one rail crossing over the opposite rail). what happens is the locomotive wheels being the pickup for AC power getting to the decoder under the hood where the decoder then rectifies and sends DC power to the drive motor.
The decoder also has control of the various lights, as well as the sound system built in to the locomotive.
So back to the issues you can run in to as I did once my layout was operational. While operating the locomotive, and when going through a turnout at scale speeds (really slow), on occasion while one end of the locomotive (truck assembly) was on the frog, power would be momentarily lost causing the sound to go dead, requiring that I restart the locomotive with the controller giving me the sound back.
Now I have to tell you this proved to be quite annoying to say the least. After various attempts at fixing the problem, and improving the situation through installing extra feed points (AC power) close to the turnout, the problem still persisted.
Realizing that I needed to power the frogs to solve the problem, it would also require a circuit with several switch's for reversing polarity when the locomotive powered through the turnout. While doing an Internet search on the subject, I became aware of a device called a "Frog Juicer" as I pointed out to you seen in the photo.
This board is an automatic polarity reverser with outputs for 6 frogs. Setup is simple, connect two wires to the DCC bus (red and black wires) and one wire (green wires) to each frog. When the locomotive crosses the turnout and if the frog is the wrong polarity, the frog juicer will reverse the polarity quickly allowing the locomotive to continue to operate normally without lose of sound as in my case.
The polarity shift happens so quickly (300 microseconds) that the DCC controller does not react by blowing a fuse, but continues to operte normally, and more importantly, all the issues with drop outs in the turnouts have been resolved, with the locomotive able to creep through the turnout at the lowest setting on the throttle without losing the sound.
With the problem resolved, its time to get back to playing train engineer!
Expand the photo for a closer look.....
The top side...…