Blocks, Block Wiring & DPDT Toggles

Blocks,  Block Wiring & DPDT Toggles – Control Panel Basics with an added bonus or two.   Also an introduction to DCC.

I heard you asking:  Why would I have both DCC and Analog DC in the same discussion?  Good question.   Uhh…err…because I didn’t make the video.    Not to worry.   You’ll find both the Analog DC with DPDT’s and the DCC way of doing things in the first video presented here.   A video courtesy of  Green Frog.  You will get a brief introduction to DCC, translated, “Digital Command Control,”

Traditional Wiring and/or Block Wiring  is   presented.   The author of the video uses a   “Double Pole Double Throw, Center Off toggle,” for the various blocks he wants to wire-in.

FYI:  You need to know. For sake of this presentation I will use:

  • DPDT in place of “Double Pole Double Throw, Center Off Electrical Toggle”.
  • Switch, in place of turnout.     I’ve  never heard rails / railroad employees, use “Turnout,” to describe a “Track Switch.”  It is simply called a, “Switch“.    For sake of discussion here I will use either “Track Switch” or just “Switch”.

The following  video presents a written introduction to the  wiring basics.   Don’t miss-out on  the discussion and presentation that follows.   Illustrated how-to’s, for block wiring  and wiring-in  a control panel.   Do note the gaps as illustrated in the video picture below.

Building a Model Railroad Series #5–Wiring & Command Control

Uploaded on Dec 3, 2008

Purchase at —
This video begins with introduction to command control and its primary differences with the basic transformer. A.J. Ireland of Digitrax makes it simple with easy to follow steps as he shows how to install the decoders in several locomotives. Next, wiring of the Apple Valley Branch track is shown complete with a reversing loop.   I hope that helps and thanks for watching, GreenFrogVideos.  

The video is for sale so feel free to do an oogle google search or go to the website indicated above.

A DPDT  switch.  Learn how to hard wire it in and it will allow you to wire-in Analog DC and /or DCC for the purpose of either shutting down power to the tracks.   With multiple uses for any other  purpose as you see fit.   For example:  The track where you store your locomotives or diesels.   The old school way of wiring-in two cabs Cab A & Cab B, to each block.   Once you learn how to wire them in and isolate one cab or throttle  from the other. You will discover the fun you can have with analog DC., dual cab operations.

For Block Control:  This is  the type of DPDT Center Off Electrical Toggle Switch that I prefer to use and highly recommend.

DPDT 2 Center OffDPDT 1 Backside


  • High Current Ratings 20 Amps @ 125vac
  • Screw Terminals x 6
  • DPDT On-Off-On
  • Illustrations courtesy of seeDPDT Center Off.

Disclaimer:  Of course with DCC,  some of the toggles you’d use for Analog DC,  won’t be necessary.

Analog DC:  So, I hear you saying  you want to stick with Analog DC.   Something about DCC makes you uncomfortable.     I understand that and you aren’t alone.

Thanks to a mentor who showed me how easy it was to wire in  Cab A and Cab B..     I soon  had it figured out and the layout up and running smoothly.   I still operate trains this way.

***You can expect wiring to be tedious and mundane but the rewards are awesome.    The key is keeping the polarity the same all the way around the layout.***

Blocks:    What are they?

Here are some things that made it  easy for me to  transition from a Toy train layout that didn’t have blocks to a  Model Railroad, with blocks.    Are you ready to make this happen on your layout?

What is a block?  This was a question I had early on in my model railroading… in-experience.   I heard my family of rails discussing the various blocks and sidings they work.   Where they would wait in the hole, for an oncoming train or make switching moves spotting a train car or two and picking up car loads.

The answer I got shouldn’t of surprised me.    They said, “It’s a small square toy with alphabet letters on it.”   Thanks a lot guys.  Hee Haw, Hee Haw, Very Funny!   The concept is not so dissimilar.   Did I just do a simile?

Putting all that behind me I persisted with my question and learned the following:


The simplest answer is they allow you  to  keep a safe distance between one train and another.   Trains are to remain one block apart.   They are also called Control Points on the 1:1 foot scale.    On most railroads the block starts and stops on the diverging end of a switch.

A Rails Perspective of a Block:

My family of rails / railroad employees talked about a “Block,” describing what it is and/or  isn’t.     The best example of this is:   Most blocks on the mainline of a  railroad are approximately one to two miles in length.    Longer or shorter in specific settings.  IE.,  Such as a long  run through siding.   Long enough to hold the longest freight out there.      A set of signals protects each block.  Either the ATS,  ATB, CTC or a Track Warrant system will protect each train movement through each independent block.

What a block isn’t:   Run through yard tracks, yard ladders, rip track,  industrial spurs, set out tracks, dead end spurs and roundhouse tracks.    Yard tracks are usually known by a number IE.,  Yard Track #1.   Industrial spurs are known by the company they serve IE.,   A&P Canning Company spur and so on.

Rule Exceptions:  There are exceptions to most rules.   One example:  A dispatcher will give permission via a track warrant, to allow a second train to  proceed into a block already occupied by the first train, to operate or move up close behind it.   With rules requiring slow orders, to prepare to stop and avoid fouling  the switch on the main.    To move up behind said train for the purpose of allowing a third train with priority orders headed in the opposing or same direction to pass by safely.     During the era of shorter trains this worked out just fine.

Train Orders:   Historically,  train orders were  written on Flimsies (on real fine paper in triplicate)... by station agents, who  hooped them up to the train crews.   Today it’s done by signals along the right of way and radio communications.    In earlier times, the Flimsies would direct crews and instruct them as to which siding they should take and what trains to wait for.   Also locations  where the track speeds  are slower –  Slow Orders.   This is where slower track speeds are required,  for on going track maintenance usually due to MOW (Maintenance of way) crews often referred to as track gangs.    Alerting to the  presence trackside and/or working on a broken or misaligned piece of track.   After passing such a location to proceed back to normal track speed.

A Model Railroaders Perspective:

Control Panels:    The real railroads use a control panel and so will we.   We need to talk about a control panel and how it works.    Asking myself what can I use here that will help you understand the purpose of and function of a control panel?   For those of you who are having a hard time relating to the whole idea.   This may  be the tough or difficult part for you.

I didn’t think we needed a control panel for DCC?  My favorite heckler is asking.   You are correct if you use the DCC decoders for switch machines.    Then it’s all in your hand held throttle… but… you may not like it.   You may find yourself having to look up the switch you want to throw and control the train at the same time.   If that doesn’t work for you…  yes, you will need a control panel.

I’ll see if I can find a picture of the Mini DPDT’s, I like to use to activate my switch machines.    Ah, here we go, found one and a resource you can use to buy yours.

Mini DPDT’s


Mini-Toggle Switches DPDT Spring On – Center Off – Spring On

Picture courtesy of We Honest and he can be found on E-bay.   See:

I use these mini DPDT’s for switch machines / solenoids that need a momentary on, to throw the switch.    IE., Kato and Atlas switches.   You will need to install these into a control panel.  Preferably a map style control panel.    OR you can throw all your switches by hand.    For example:  (1)  Atlas switches need to be wired into the AC side of your power supply.     (2)   Kato switches will need to be wired into the  DC side and  wired to  reverse the current, center out, hot to the switch machine.

Control Panels and Blocks:

Back to blocks and how best to wire them in.  So, let’s introduce you to the basics, how-to wire in a DPDT and the making of  a control panel.

Looking out into your faces, I can tell, I really can.    Those of you with paid tickets to hear this presentation are following along and catching on quickly.   For those of you following along at home as free loaders.   What?   What?  What did I say?   You fine folk…  appear to be teachable.    You’ve learned well…so far.   I said with a reassuring,  Grin!

Blocks Start and End At…….

You did ask, “Where does a block begin and end?”   You didn’t?   Ok! You did!    Allow me to  explain how this works.

Most begin and end at a switch as in “Track Switch.”  The block begins or ends on the diverging end or the frog end of the switch.  Where the tracks split.

At a point that is safe where two trains, one that occupies the main and the other the  siding, so they won’t collide, side swipe and I’m sure there other examples you can think of.  Keeping in mind they  aren’t allowed to foul the switch or occupy the switch while stopped.  For example:   Looking toward the diverging side of the switch, a little ways after the two tracks separate.    Most railroads have a clearance requirement as to how many feet back from the switch a waiting train is  required to be.        On most model railroads this will hold to be true as well.

On a model railroad the blocks will be isolated  from each other.       One DPDT toggled electrical switch per block.   Both rails per track will be cut, just short of the switch creating an isolation gap.

I think I’ve already emphasized the following but it’s worth repeating.    I won’t cut a switch track rail,  as illustrated by other authors.    You are just asking for trouble.  I will move back from the switch and cut in the isolation gaps into the attached track.    I did say on the diverging end of the switch?   I did?    Good!

Diagrams  Illustrations:

Here is a diagram that may help you.     Dual cab control.  Cab A and Cab B…with power packs isolated from each other.   Note the color code of the wires.   Cab A,  Red and Green.   Cab B, Blue and Orange.   You can click on the image to enlarge it and the fuzziness will correct itself.

Cab A Cab B DPDT Wire Diagram

Do note:    How they set up the blocks for the tracks.    Also note how the blocks are cut in just behind the diverging end  of the switches.  Credit for the diagram above goes to  TY’s Blog.

Allow me to share some pictures from my layout.    A work in progress even as I write.

Oh dear, someone talk me out of doing this.   Quick!   Am I really going to show you this?  To late.  May a higher  authority help us all. Just so you understand it isn’t (is not) always about how clean or organized your wiring looks but that it works.    It doesn’t need to be an art project.

You can click on the picture for a larger image.


In the first  picture above, up toward the middle top, you can see an “A” and to the left  of it a “B”.     This is where two sets of wires for Cab A and Cab B come in to the backside of a temporary control panel.    You can also see M1, M3 and MST.   These are out going wires to my  independent blocks on the mainline.


In the second photo above, you can see how my wiring is color coded and bundled.    Making it easy to trace a set of wires and look for problems.   IE., A worn out spot where the  insulation has gotten old and rubbed off with two wires rubbing together to cause a short.    Often referred to by some electricians as an “Accumulative Short.”  As it accumulates over time to become a short. I’ve never seen or had that happen  but there’s always  a first time.

Wrapping or winding your wires together?   Right about here might be a good place to say… I don’t, as in do not, wind or wrap my wires around each other.    You can see that’s true in the pictures above.    I see no benefits in doing such and view it as something similar to superstition.    Although, many hobbyist have been doing this longer then I am old.    I don’t need to go back to basket weaving.    Although, I’ve seen some mighty fine work by my native brothers and sisters.

What you don’t see in this picture is the backside of the control panel and the DPDT’s, center off, electrical toggle switches.  Film uhh…err…photos, at eleven but don’t hold your breath.

That was quick, I found them.   Here is the photos, I promised.   Good you didn’t hold your breath I don’t see any bluish-purple faces out there.    No one needing CPR, whew!

I’ve found this control panel useful when mentoring a newbie.  This control panel is one of those I’ve used as a teaching tool and/or temporary control panel.     I color code my wiring,  the Red and Yellow (Yellow) is Cab A and  Green and Blue is Cab B.


Pretty easy to follow the wiring  in the first photo above.    The clear wires with tails going to the bottom of the picture, are the ones that go out to the track blocks.    You can click on the images for a larger and clearer picture.


The second picture  is the face of the control panel.  Commonly referred to as a straight line or linear control panel.    Looking at the toggled electrical switches.   # 1 is set to center off.    #2, #3 and the Yard Lead are all set to Cab B.      Cab A to the left and Cab B to the right.   Should you place Cab A to the left of the control panel and Cab B to the right it will feel down right natural.

For now do ignore the Atlas Blues and the smaller push buttons,   which are momentary on.    They are to activate the solenoid in  the Atlas switch machines.   The blue sliders are a  poor way to do this but works fairly well as in… okay.   Sort of…!  Newbies can use them to get acquainted with wiring in their switches.  Downside:  They can wear out and or  get stuck to ON and burn out the solenoid in the switch machine.    Don’t ask me, how I know.   I didn’t know switch machines had built in smoke generators.

A model railroad will have dozens of blocks depending on the owners perception of how to use them.      It will be about How many  trains  he or she feels they need to run at one time and/or have on the layout at any given time.   As in multiple sets of trains.

To much information, to quickly?   You’ll find other posts here where others build different kinds of control panels.   Feel free to look through the categories and browse to your heart’s content.  I’m counting on you to grasp how this works and figure it out for yourself.

You won’t learn anything if you don’t get busy and build your own control panel.    Trial and error although frustrating can be a good teacher.   More to come so don’t give up on this project, yet.


Splicing and Isolating the  wires:

As much as possible,  I want my home runs to be one continuous piece of wire.    Highly recommending such.      Of course 18 gauge wire or  bigger is better but I do have some 20 and 22 gauge wire on my layout on short runs.      The idea is:  Larger wire equals  less in-line resistance or power drop.

I’m a die hard solder, kind of guy.    I don’t much care for suit case connectors or wire nuts.  Now being recommended by electricians.    Why?   I’ll get to that.  Soldering:   Downside they took the lead out of the solder which is what conducted electricity.     If you solder you need to make sure the wires touch.   So suitcase connectors and wire nuts are in and feel free to use them.

Wire Tubing or Shrink Wrap and Electrical Tape  to isolate any  splice and you can find such in the pictures above.     Here’s some examples:

Picture courtesy of, see:    Shrink Wrap – Wire Tubing.

Colored Electrical tape to isolate my spliced wiring.    If I haven’t already said, It’s all about color coding my electrical wiring.

Picture is courtesy of,   see:   Colored Electrical Tape.

Blog Tutorial:   If the print is red you can click on it and you will find your self high-balling to the recommended post.      Do remember how to get back.   You know the box and arrow thing.

Helpful Tips:

Switches or Track Switches and Rail Joiners:

Caution:    A word to the inexperienced  newbie and perhaps affirmation for some of us who know better.

Cutting Isolation Gaps in the Switch Mechanism:    By now you may of seen a How To  Video or read in a model railroad wig wag how some guys and gals talk about or demonstrate how-to cut in isolation gaps,  in the switch mechanism. Where they will  cut in isolation gaps specifically before and after the frog.  I don’t recommend it.   Especially for  any in-experienced hobbyist.    Do not attempt to   dissect a Peco or any other switch track… pre-mortem.   Not at today’s cost of switches.   

Best advice of the day, leave them alone!  Unless you want maintenance issues down the road.    There is a much  simpler resolution to the perceived problem.   More on this in the presentation I make here on, regarding  DCC Friendly Switches.

Using rail joiners with wires soldered to them.    You saw an example of that in the video.    Again, something I don’t recommend.  What happens if you need to solder the rail joiner to the rails?    I think you can figure that out.   Where did the wire go?   How come I don’t have any power in this block?   You can visit Soldering Procedures here on to see a better way to accomplish the same thing.


Bonus:    This may or may not help!

For those having trouble wrapping their heads around the idea of a control panel.

It can sometimes be difficult to wrap ones head around the idea of a control panel and how it should work.    There are those who’d rather wire in directly to the track and just run trains in a circle.      If you want more then this and are still having a hard time understanding the concept of a working a  control panel, the following may help.

Control Panels – Comparatives:

When it comes to a control panel I have, what I hope are some helpful verbal pictures with some illustrations and comparisons to look at.

A car has a basic control panel.  Although that’s all changing with the advent of electronics and an assortment of gizmo’s.   All there… to distract the driver from his primary purpose…driving the car.  Airplanes have advanced and complicated instrument panels.    Air controllers have complicated screens to work with.    Railroad,  Yard Towers and Dispatchers  have some rather complicated control panels.    As will our toy trains or model railroads.    I know not the kind of news you were hoping for.

Have you ever played some sort of instrument?

  • Music as in playing a piano or organ.   Whether it is singing a solo,  or being a part of a  quartet or choir with four part harmony or a variety of options thereof.  You have to be able to read and follow the music and present it, as it’s written.  I know that in order for me to get a harmonic sounds out of either a piano,  electric or pipe organ, I have to play or press down certain keys to get the harmonics I desire and pull certain stops to get the sounds I want.     See: “Screwing Around.”  Drop down to the video with a Pipe Organ in the picture.    You’ll get the idea.

I look at a control panel for my model railroad, in the same way.    In order to get my trains to move through various routes on my layout I have to pre-set the toggles to specific settings.   Toggling track switches and setting various block toggles to Cab A or Cab B..   All dependent on the throttle I’m using and the route I wish the train to take.  Done correctly  my trains will move freely around the layout without peril to each other.    You know…crashing.  I might add here this is by far more simpler then trying to play a piano, organ or other forms of key boards.   Using of course the same principles.

Wiring in DPDT’s electrical toggle switches.    Once I learned how to hard wire in a DPDT electrical toggle switches and solder them in, it was off to other adventures,    Wiring a car IE., Adding fog lights to my car, putting in a stereo system and much more.    Mom wanted lights in the kitchen over the sink…no problem.    Keep in mind only one individual toggle or electrical household switch is used for each function mentioned  above.

  • Sound boards:   To clarify not DCC sound boards.   Control panels for on and off activation of microphones for live performances on stage.   Some of the teens and I got together and put together a  type of control panel (sound board) for powering up microphones.   To be used for  church meetings, small acoustical bands, various plays or skits and a choral group or two.    A lot of what we did was not so dissimilar to the control panels, I made for my model railroad.     We used DPDT electrical toggle switches  and pots, to control the level of sound desired.    Did I mention home made control panels?    Not the best in the world but it worked.   Finally, Radio Shack and Mackie came out with some excellent sound boards and it was possible to eliminate the feed back aka squealing.     Well…in the hands of trained operators and sound checks prior to the event.   You guessed it.    Trained operators following proper procedures.

Trained Operators:  Precisely where we need to get you to.    That’s what I wish for everyone that reads this.  Now getting sound technicians trained….that’s a bit more complicated and another one of those stories for another time and place.

  • With the right control panel on your layout and a complete understanding on how to use it you can begin to enjoy the benefits of model railroading.     For some of you, this will be an extremely difficult learning curve while for others  building your  control panels will be a snap.    For those who catch on quickly…heck, you might teach me some new tricks.  I might learn a thing or two from you.

I hope this helps to get you started and headed in the right direction.   As a reminder there are other examples of control panels and how to build them here on    Be sure to take time out to meander, gander, browse and as they say today surf to see what’s possible.  Although the original form of surfing was by far more fun then today’s  version.

For a glimpse of the 1:1 foot scale in action.   Check out:



News Alert:   Pardon the interruption.  

There’s a reason why I have added links to the items mentioned above.  You are going to need them and here’s why:

Radio Shack Bulletin:  I need to add here the things we took for granted and purchased  from Radio Shack, in the past, are no longer available.  Things are disappearing off the shelves and at a faster pace then I thought possible.   Our local store is closing.   A real disappointment.    The corporate suits decided to leave behind the items that built Radio Shack.   To create a new corporate image and  turn it into a telephone store.  A lot of us told corporate they were making a mistake.   Nobody was listening.   Phones?  You can only saturate the market to a specific point before everyone has a phone.   They had a great market for  Radios,  (C.B. & Ham kits)   Stereos, Home Theater sound, superb speakers and amplifiers.   Scanners to listen into the Railroad chatter between the dispatcher and crews.   With  many of the electrical components, gadgets and those essential 12 volt DPDT’s.     Stuff made  for private home use or building a public address system. Gone.  Some can still be found on their website but don’t expect that to last very long.

I used to work for Radio Shack, as an associate for a store in Kettering, Ohio.    Loved it and we had great stuff to sell.   The training was questionable but the information shared with us is still useful to this day.     As our local  Representative and Associate here in Big Bear Country said, “We don’t sell those things anymore.” Gone!  Mark my word, a mistake but they didn’t ask me.  Say good bye to an old friend.    Sigh!

This is not a paid  political announcement.   Nor is it meant to slander R.S..    Not my fault they can’t see there way out of the box.

Enjoy your wiring projects and thanks for stopping in to give us a read.    I hope you found the information here helpful.   Do note the resources I gave you to find and purchase your own electrical gadgets.


Photos of wiring and control panels are courtesy of myself aka Rick Howland.   Video courtesy of GreenFrogVideos.     Other graphics and credits are already noted.



  • Great information. I just recently started to rewire my initial layout to DCC. Is it ok to connect the DPDT momentary switch to the Kato switches using 18 gauge wire? Their switches are wired with 22 gauge wire (red/black) as is the track power connectors (blue/white) I prefer the 18 gauge stranded copper but will the current bottleneck when it reaches their 22 gauge connection?

    • Hi Barry,
      To answer your question the simplest answer is yes. Smaller gauge wires typically means line drop and power lose as in acting much like a resistor. However, in the case of larger wires feeding smaller wires we do it all the time. For example with our track, we use small gauge feeder wires to the rails, connected to larger bus wires. Not a problem. Do Keep in mind that Kato Unitrack switches operate on DC and you will need to use a DPDT, wired to reverse the current.
      I hope that helps.

      • Thank you for the prompt reply. Very helpful indeed. Yes, I am aware of the need to make a crossover on the switch and my power supply will be from a AC/DC kato converter.

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