Control systems

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  • THE FIRST MISTAKE: Model railroaders as a rule do not design their control systems or develop a CONTROL PLAN with the care they put into their track plans.
  • THE SECOND MISTAKE: Model railroaders as a rule have spent the bulk of their "control" efforts dealing with the electrical requirements created by using the track to power the locomotives. In fact, this is only part of a complete control plan.


These definitions are not "official". They are here to help get ideas across. I am trying to avoid assuming that everyone understands these concepts, so please bear with me...

  • CONTROL: The ability to start, change, and stop something. Communication with or information about the thing being controlled is a vital part of control.
  • DIRECT CONTROL: Using your own hands, eyes and ears on something to control it
  • INDIRECT CONTROL: Using your hands, eyes and ears on some intermediate device to control something else. Note well: control can range from totally direct (push your loco by hand, shouting choo,choo!) to completely indirect (fully automatic display operation).
  • CONTROL PHILOSOPHY: An individual's or group's preference for a certain ratio between directness and indirectness of control of the various parts of the railroad.
  • CONTROL SYSTEM: BOTH the various direct and indirect means used to effect control on a model railroad AND the various direct and indirect means used to provide or obtain information about the things being controlled on the railroad.
  • CONTROL EQUIPMENT: mechanical means of control. (Ground throws, for example)
  • CONTROL TECHNOLOGY: A packaged solution for a particular control problem, usually electronic or electrical. (Examples: Block control, DCC, or an electronic circuit made to run the trackside interlocking signals around a turnout)
  • CONTROL INFORMATION: Data about thething being controlled which is presented to the operators of the RR. It can be obtained directly, indirectly, or by some combination of the two. (Train speed, train location, route status, block occupancy,turnout position, etc.)
  • CONTROL ACTIONS: Control actions are direct or indirect things you do to the railroad, other crew members or the control system to start, change or stop something on the railroad. (What you do.)
  • CONTROL INPUTS: Control inputs are parts of the control system (or maybe even other crew members) you manipulate or act upon to make the control system (or some crew member) start, change or stop something on the railroad. (The thing you do it to.)
  • CONTROL EFFECTS: Control effects are the desired starts, changes and stops which occur on the railroad.
  • CONTROL OUTPUTS: Control outputs are the various forms of indirect control information presented to the operators by the control system.
  • CONTROL DISPLAY: An electronic, electrical, mechanical or graphical means of presenting non-direct control information to operators. (Examples: full-bore CTC machines, magnetic tag boards, trackside signals, control panels with indicator lamps or meaningful toggle positions/labels.)
  • CONTROL PLAN: A description of the ENTIRE control system, describing ALL of the direct and indirect means and information to be used by the operators to control the railroad. This may be broken down by the different jobs people have to do on the railroad, and for the different modes of operation that will occur on the railroad. This may include the control information, displays, technologies, equipment, actions, inputs, effects and outputs and how all of these things work together to help people operate the railroad.


The best solution

The right way to design your control system is to figure out exactly WHAT you want to do and THEN buy or create the best means to do the job. Many companies sell and modelers have themselves developed various solutions to meeting the electrical requirements for making trains move. None of these technologies or techniques are control systems in the full sense of the term. These solutions are tools, or building blocks, which should be a part of an intelligently designed control system.

Built using consistent rules

A control system is a machine built using rules to carry out instructions. "If this is done, then do that." Rules need to be developed and used so there is consistency in the way that the controls work. (For example, "The top pushbutton always selects the mainline position for any turnout") If you do not think through the rules or instructions you want to have carried out, the system may not work at all, or it will be very confusing to operate. In this regard, control system design is like computer programming.

Easy to use

To enable as many different people to participate in the various activities involved in running the layout, all of the controls should be easy to learn, understand and operate.

  • Clear and logical: Further, clear and logical identification of controls, and consistency of control design and construction is important.
  • Good labels: Where many people are operating, try starting with temporary labels or graphics, and then modify them as operation on the railroad point out spots where operators have trouble understanding things. Once the dust has settled, make the labels and graphics permanent and presentable.

Indirect control

  • Indirect costs more: More money and effort will be required to build the control system as more indirect means of control are used.
  • Indirect controls more efficient: Indirect control is used by real railroads to make jobs more efficient. Examples include Centralized Traffic Control, and automatic block signals. Consider adding wiring and circuitry to make the job simpler or more efficient for the operators on your railroad. Wiring the controls for a complex yard ladder so that one pushbutton operates all of the turnouts for a desired route is one example.
  • Indirect means more to learn: Usually more labels, diagrams, and instructions will be required for operators to do their jobs as a control system becomes more indirect. However, in a perfect world, the best indirect control systems are transparent to the users, giving the feel of direct control with no awareness of the control system. This is accomplished by working hard to plan and arrange the control system so that the controls are intuitive. This occurs when control appearance and arrangement explain their function, making labels and intructions unnecessary, or when a complex but unchanging series of steps required to do a specific job is automated. (Again, think of the yard ladder route set with one pushbutton.)
  • Indirect hides complexity: To paraphrase the Japanese author, Shirow Masamune: "Functional simplicity, structural complexity: the best railroad for all." Try to use technology to move the complexities out of sight of the operators, so that their jobs stay as realistic, yet simple, as possible. Command Control technology is a good example of this. The electronics involved are complex, but the controls the engineers use can be as simple as a hand box with a speed control knob and a direction switch.

Visual feedback of controls

Some control system design issues affect other areas of layout design. Train position information by visual means demands avoidance of hidden trackage and good operator sight lines. Manual turnout control means that turnouts must be located where operators can reach them easily. Ditto for manual uncoupling of cars. Signal locations and visibility must be arranged so operators can get the information those signals are supposed to provide.

Selective compression of controls

The laws of physics and a concern for safety often make real RR control systems very complex. However, model RR controls can be considerably simpler than the real thing, and still provide prototypical flavor, safety, and enhanced traffic flow. Selective compression of a control system can be a good idea.

Input devices

Here is a partial input device list: speed controls, direction controls, turnout position controls, uncoupling controls, means of "setting the brakes" on rolling stock on grades, means to control locomotive lighting and/or sound, means to control signals, means to control lighting on layout and for layout. Telephone, radio or other means of communicating with other RR crew, (including hand signals.) Any of these could be direct or indirect.

Output devices

Here is a partial list of control effects/outputs or output devices: Train speed, train direction, turnout position changes, block power assignments, occupancy indicators, trackside semaphores, searchlight signals, turnout position indicators on a dispatcher's board, bells, horns, telephone, radio or other means of communicating with other RR crew, (including hand signals,) block toggle switches whose position tells you which cab has a block, etc.

Defining how the controls operate

This article is not about how to wire the railroad. This is a design document which will attempt to help you define how your control system is going to operate. The wiring details are covered pretty well in the hobby press, and in the documentation of the control technologies that are for sale.


Your control system design can be based on the ways that you or other modelers like to operate trains. This is a partial list of operating modes. Add or delete as you require for your RR.

  • FULL DRESS: There is a dispatcher or dispatchers in a remote station making the prototypical decisions of how traffic flows, while train crews run their trains along the line. Yard crews are making up and breaking up trains, and servicing locomotives and rolling stock. On many club layouts, this mode is the public show mode, a time when many club members are on hand. On private layouts, this is typically the mode when the most intense, realistic, and challenging operation occurs.
  • INFORMAL GROUP: People run trains with no official dispatcher. Engineers might be sitting in one spot, or they may be walking with their trains. Visiting railroaders usually get to operate at these type of sessions. This could extend up to a "wayfreighting night" at a club layout.
  • SINGLE OPERATOR: One or a very few persons are doing their own thing without much coordination on various areas of the layout.
  • DISPLAY MODE: One or a very few persons run trains over the layout for guests to view.

Figure out how the control system will accomodate each operating mode in your list.

Walkaround operation

Walkaround Operation is very desirable for people running wayfreights doing setouts and pickups around the railroad.

  • Wayfreight operation: The control system should make this job as pleasurable as possible. Wayfreight operators should be able to blend smoothly into the activities of the rest of the railroad, with only the prototypical problems of clearing the mainline, etc. to challenge them.
  • Disconnected operation: Control techniques such as memory-walkaround or wireless throttles are often used to assist in this regard, as the engineer does not have to deal with a wire constantly connecting him to the RR.

Elevation control areas

Operation from Elevated Control Areas can be difficult if the engineers cannot know the status of the track ahead of their train. Further, some sort of control of mainline turnouts and places where trains start and finish their runs will make Informal Group or Solo operation from an elevated operating area much more fun.


If you have not developed a good control system, forms of feedback like angry, frustrated operators or the sound of rolling stock falling to the floor will let you know that your control system may need a little more thought and refinement. If you see someone making a mistake in operating the railroad, look at that as an opportunity to improve the control system. At some point the law of diminishing returns will come into play, but often simple changes or additions will make big improvements for the operators.


Asking the important questions

Track planners try to start off with a list of the things they feel the railroad must have, and the things they would like it to have. The same thing must happen for the control system. The "Second Mistake" usually occurs right here. "Oh, I'll use (Insert name of commercial product, or usual approach here) to run the trains." Several important questions should be asked before this decision is made!

Duplicate or simplify?

Do you want to draw inspiration from the way that real RRs do things? Is an exact duplication of actions desired, or are simplifications of real railroad practices acceptable or desired?

Period or era-specific?

Are you modeling a particular era? How did real railroaders do their jobs then? Do you want your control system to provide some of the flavor of the period to your operators?

Motion, sound, or lights?

What do you want your model railroad or trains to actually do? (Physical motion/ sound/ light?)

Automatic functions?

Should anything happen automatically?

How much skill needed to operate?

How hard should it be to operate all or some part of the railroad? Who are your operators? How much teaching do you want to do? Are there to be operators of different skill levels? Is there to be more than one way of operating the railroad?

Developing answers

Get some answers to these questions worked out. Think about different model and real railroads you have seen, read about, and operated or ridden on for ideas on what to do, and what not to do.

List the functions you want

In light of your Givens and Druthers, make a list of equipment or conditions which you want to have your operators control. Here is a start; add or delete as needed.

  • locomotive speed
  • locomotive direction
  • locomotive lighting
  • locomotive sounds
  • locomotive and car coupling and
  • uncoupling
  • brakes on rolling stock
  • turnout position
  • scenic sounds
  • signal aspects - lighted, semaphore, etc. (appearance)
  • lights on layout (scenic)
  • lights for layout
  • animation on layout
  • occupancy indications
  • position/location of trains, locomotives, or cars
  • animation effects


Consider the various types of crew jobs and operations your Givens and Druthers establish.

Write a description of each job

Key to the description is spelling out what you want that person to do, and what information they need to be successful in their job. Do not assume that the operator knows anything! Spell out where the operators are, what they are doing, and how they receive the necessary information. Take into account direct and indirect means. Add, delete or modify the following to match YOUR "givens and druthers."

  • DISPATCHER - Insert description of the control actions, inputs, effects and outputs this person will have to deal with to do their job.
  • ENGINEER(In elevated operating area, A.K.A. "aerie") - Ditto
  • BRAKEMAN - Ditto
  • CONDUCTOR - Ditto


Straight DC

When two electric motors are directly connected to the same electrical power transmission system, there is typically no way to operate the motors separately. Two regular model locomotives and two regular "powerpacks" cannot work independently on one plain, solid piece of track. Here are the common solutions: (Let's pass over wooden trains, shall we?)

  • Give each train its own loop of track with no connection to any other train's track. (Catenary (overhead wire) or a third rail is used very occasionally as a means to run two independently-controlled trains on one track.)
  • Establish a "block system," with the track broken up into electrical control sections, which are often called blocks.
    • A throttle can be permanently assigned to each block. The person(s) running a train then have to set speed and direction correctly for each block for a train to proceed through to the next blocks
    • A means can be provided to connect an engineer's throttle in turn to each block on the railroad as needed to run that engineer's train. There are many different techniques used to do this. They range from the simple commercial solution offered by Atlas with their "Electrical Controls," to complex and powerful computer interface systems which can literally do anything that you want to take the time to program them to do.

Use Command Control Technology

Systems which send power and messages over the rails to devices in locomotives or at other trackside locations are known as command control systems. ( A carrier control system is a type of command control system where the control data is superimposed on a "carrier signal.")

  • In practice, one person's or several person's commands (speed, direction, turnout position, etc.) are electronically combined, and put on the rails all over the railroad. Devices in the locomotives act only upon the messages sent to them, using track power to do their jobs.
  • This allows much greater flexibility in the operation of model locomotives, as two or more locomotives can be right next to each other, yet be controlled by different people. They typically can also be run together under the control of one person.
  • With command control, layout wiring can be simplified since the need for blocks is reduced. However, command control may not be a complete control system for you! Check your givens and druthers.
  • The National Model Railroad Assn. has adopted a standard for putting power and digital information on the rail. This is called the Digital Command Control (DCC) Standard. The standard allows different manufacturers to produce digital command control components which can work well together. Company A's "digital command station" will correctly control company B, C, and D's "digital decoders" installed in different locomotives.

Radio-linked control

  • Radio control of a locomotive, where the radio reciever is carried in the locomotive. The power could be provided either by the track or by batteries in the train. Block power routing concerns are eliminated. The operator is also freed of dragging cords.
  • Radio control of a throttle, where the radio reciever is mounted with the throttle under the layout. The throttle power could be connected to the locomotive by any of the usual means. Typically, this approach is used to "cut the cord" between the operator and the railroad.

Infrared-linked control

  • Infrared control of a locomotive, where the infrared receiver is carried in the locomotive. The power could be provided either by the track or by batteries in the train. Block power routing concerns are eliminated. The operator is freed of dragging cords.
  • Infrared control of a throttle, where the infra-red reciever(s) are mounted around , on , or above the layout. The throttle output power could be connected to the locomotive by any of the usual means. Typically, this approach is used to "cut the cord" between the operator and the railroad.

Use your Givens and Druthers to determine which of the above is best for your railroad, and if a particular manufacturer's version of any one approach is the "best fit" for you. A partial list of the always-changing field of manufacturers of model RR control stuff (I love the word stuff!) can be found in Appendix B.


Appendix A - References

Appendix B - Vendors

Appendix C - Gapping the Rails

Appendix D - Thoughts on Model Railroad Control Systems

--by Mike O'Brien


I hope that the above article starts you on the way towards developing the right control system for your railroad. You may decide this topic is not as interesting to you as others in our hobby, but please give it enough attention to ensure that your railroad is reasonably easy to run for you, your friends and your guests.

   David C. Gibbons, Copyright - 1996
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