The basics of Lionel Legacy / TMCC and MTH DCS

The basics of Lionel Legacy / TMCC and MTH DCS

It’s all about control. Locomotive control, that is. When it comes to O gauge model trains, there are quite a few different ways of relaying your command to the locomotive. There are positives and negatives with each method, and if you’re new to model railroading in general or O gauge in particular it might be confusing to see all these options. Can a Lionel throttle run an MTH diesel? What’s DCS, or TMCC? Hopefully this short article will be able to set you on the right path to finding the best answer for you. 

Let’s start with the basics. 

You’ve got yourself a loop of track, a spiffy new 6-38684 0-6-0 Docksider, and a few freight cars. Things are looking good! How do you communicate to the locomotive that you want it to move forward, speed up, slow down, stop, or reverse? Enter the controller. 

Whether you call it the controller, throttle, transformer, or that box you plug into the wall, the most basic method of controlling your 3-rail locomotive takes alternating current from your wall socket, uses a transformer to step down the voltage from a potentially lethal 110-120 volts down to a useful and fairly safe six to 24 volts, and uses wires to connect to your metal track. The classic Lionel ZW transformer is one such example. 

Power flows from the third rail up your locomotive’s roller and into the motor, then out to the wheels and into the outer rails of track. From the outer rails it goes back to your transformer, through the power cord, and back into the outlet. If it helps, imagine a river that you’re diverting into a small channel to turn a mill’s waterwheel. 

When you move your throttle lever, you’re increasing the amount of voltage reaching the third rail. Zero volts, zero movement of the locomotive. As more voltage is applied, the electric motor spins faster, increasing the speed of your diesel or steam locomotive.

Now it gets tricky

You’ve been having a great time with your little switching locomotive running around the loop, but you’re getting a little tired of running in circles. After ordering some more track (say, Lionel 6-12031 Outer Passing Loop) you’ve expanded that loop into a big oval with a siding, and your 0-6-0 Dockside steam engine has been joined by your new pride and joy, an EMD SW8 diesel switcher, the MTH 30-20404-1. You put both engines on the track and open up the throttle, and while they both move, it’s not as fast as just the Dockside steamer used to be. So off comes the SW8 and the Dockside is moving at top speed again, and the SW8 goes great on its own, but together they’re going slower. What’s going on?

Amperage. If you imagine volts as a fast stream of water making the waterwheel move, amps control the volume of water you’re moving. This example is exaggerated, since most controllers pass enough amps to the track to run a few locomotives, but we’re simplifying things for the sake of the article. Accessories will also eat up your available amps, whether that takes the form of powered switches, track lights, or interior lights in your passenger cars. More amps means you can run more accessories. 

You’ve got both engines on your track now (or should we say layout at this point?) with the intent of using the SW8 to haul a short train around the loop, and the Dockside steamer at work switching freight in your siding. But when you open the throttle, both move in the same direction at the same speed. Either your SW8 is stopping and backing up on the oval as you switch your siding, or your Dockside loco is jammed against the end of track bumpers, wheels spinning as it tries to keep going forward. 

With a basic controller, however many locomotives on the track you have will receive the same amount of voltage and begin moving. Trying to doublehead a pair of locomotives with different size driving wheels? You might end up dragging the slower engine around the track, instead of both working together. 

What are my options?

Let’s first clarify what we want to do. We’ve got two locomotives that operate at dissimilar speeds that we’d like to run together smoothly for doubleheading purposes. Or we’ve got a loop of track where we want a passenger train going, and a freight yard we want to switch at the same time. A basic throttle won’t work here, since it sends the same amount of voltage to the entire track, and anything on the track will pick up that power and run. 

What we need is the ability to address individual locomotives and give them specific instructions on what to do. Luckily, train manufacturers have met that challenge and there are a number of ways we can talk to our locomotives. 

The two most popular control systems in O gauge come from Lionel and MTH. Let’s start with Lionel. 

Lionel TrainMaster Command Control

Commonly referred to as TMCC, Lionel’s TrainMaster Command Control system (6-12969) made its debut in 1994 and was in production until 2006, when it was superseded by the TMCC-II Legacy system. TMCC is a wireless control system that uses a handheld controller referred to as CAB-1 (6-12868), and the Command Base (6-12911) to receive and transmit signals to your locomotives. 

The wireless nature of TMCC allows you to interact with your layout in a new way, moving around while still maintaining direct control of your locomotive. Since TMCC uses a radio signal to transmit orders, there are fewer issues with power disruptions caused by dirty track. The track itself is energized to 18 volts, providing steady power for lighting and accessories at all times. 

With TMCC you can program in acceleration and deceleration curves, mimicking the inertia of a heavy train. Sound is another feature, with Lionel RailSounds featuring audio captured from actual prototypes rather than generic effects. 

Lionel TrainMaster Command Control II/Legacy

Lionel Legacy, also referred to as TMCC-II, is the next generation of TMCC. It is backwards compatible with TMCC. It shouldn’t surprise you that Legacy has more features, more controls, and more options than TMCC. Commands are sent to individual locomotives, features can be activated, switches thrown, and more. As one example TMCC offered 32 speed steps for your locomotive, allowing you to shape its acceleration and deceleration curve. With Legacy, that jumps to 200 speed steps, giving far more control over the behavior of your locomotive and making it easier to match speeds in a consist. 


MTH offers its own control system, the Digital Command System. Starting in 2000 with the release of Proto-Sound 2.0, MTH has used the same control system in all their products, from the tiniest diesel switcher to massive articulated steam engines, giving you over twenty years and counting of products that are controlled and operated exactly the same. DCS can be used to record up to ninety minutes of commands which can then be played back, letting you run part or all of your layout automatically while focusing your direct control in another area. 

Like the Lionel examples above, DCS sends signals to specific locomotives (or switches, or accessories) commanding it to perform a function. This can range from increasing or decreasing engine speed, increasing smoke output, ringing a bell, blowing a horn or whistle, playing brake squeal or crew chatter, and more. 

The primary difference between Lionel TMCC and MTH DCS lies with the transmission of the command signal. With TMCC the signal travels via radio wave through the air to the receiving locomotive. With DCS, the signal is sent through the track. 

Is one better than the other?

Honestly, not really. Each system has its own advantages and disadvantages. MTH DCS requires a bit more effort placed into wiring the track, as its signals are sent through the rails. If you’ve ever run an HO or N scale layout with Digital Command Control, it will be familiar to you. Since TMCC and Legacy communicate over the air, wiring for that system is simplified. DCS offers more information and provides two-way communication - no more wondering if that locomotive is ignoring your command or just hasn’t been placed properly on the track. 

If you have the opportunity, engage with a club and see how each system operates in person. A hands-on experience will give you a better understanding of which system is right for you. 

Do I have to choose just one? 

No! You may have to purchase more equipment than you would otherwise, but it’s possible to run a TMCC locomotive with DCS, and a Proto-Sound engine with TMCC/Legacy. Both Lionel and MTH provide information on what equipment is needed in order to control the other’s systems. You’re not locked into being an MTH person or a Lionel person, so enjoy shopping around and drooling over locomotives from both manufacturers. 

Say you have a TMCCII/Legacy system for your layout, and purchase an MTH locomotive. You can use the TR function of your Legacy remote to vary track voltage, giving you basic control over an MTH Proto-Sound engine. Unfortunately this precludes addressing other engines, and you lose access to sound controls and other functionality of the MTH locomotive. 

Controlling a Lionel Legacy locomotive with DCS requires more hardware but does allow the use of more of the engine’s functions. You’ll need to have the Lionel #990 Legacy Command Set and LCS Serial Converter 2 (6-81326), as well as the MTH 50-1003 DCS TIU, and 50-1032 TIU/TMCC Legacy connector cable. 

Many O gauge operators who have Lionel and MTH locomotives on their layout will simply use both types of controller, in order to access all the features of each brand’s locomotive. So don’t be afraid to experiment and see if one or both is the best solution for your model railroad.   


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