MTH (Mike's Train House) DCS (Digital Command System)

Note: much of the information and tips come from Raymond Manley and John Allman, thank you guys!


This is an interesting, highly featured digital command system that uses constant track voltage.

The power and command signals ride "on" the track voltage, they do not "modulate" the track power as in DCC.

(DCC uses a variable frequency square wave as power and signal, very much like FM radio).

There are certain advantages and disadvantages to this method, which I will expand on in the future.

The sounds and "gadgets" are kind of at the top of what is available in large scale. The recordings are excellent, and the motor control is good, and the system actually uses a optical tachometer timing strip on a motor flywheel to set the exact speed requested.

Basic system components:

  • A power supply
    • Most people choose a very well filtered DC power supply.
    • Filtering is more important than voltage regulation in DCS, it is an electrical noise issue due to how the signal "rides" on the power.
  • A TIU (Track Interface Unit)
    • Can pass power through, or just connect to the track separately
    • "Adds" the control signal to the track power
  • A remote control / throttle / cab
    •  These work wirelessly but can be tethered
  • A DCS-equipped loco.


A bit on the way the signal works:

For most people, they just want to have the system work, and there is no need to understand the "guts". I have been watching and reading and helping people with problems with DCS.

The basic design of how the signal is transmitted is, in my opinion, one of the fundamental reasons for problems. Basically, there is a constant track voltage, AC or DC. The DCS signal is a RF (Radio Frequency) signal at about 3.27 MHz that "rides on" the constant track voltage. This signal is about 2 volts peak to peak. (In contrast, the DCC signal is about 20 volts peak to peak). Since the signal is high frequency and low voltage, it is sensitive to electrical noise on the track, and to poor connections, which cause the signal to "reflect" or be distorted.

Here's some shots of the signal by Ray Shoop:


Tips on configuring the system

(Thanks to John Allman)

  • The first tip is that polarity of the power is VERY important. Make SURE your power supply leads are marked well so you always hook the proper polarity to the TIU. I'd recommend black and red banana plugs. Most people supply power through the FIXED 1 input, but you can use the VARIABLE 1 input also. (I believe that if you do not use one of these, you basically cannot "find" the TIU).
  • The polarity on the track is also of paramount importance, if it's wrong, then you need to reverse the track polarity. The symptom of wrong polarity is the loco just takes off and will not respond to control, and cannot be "found".
  • If you want to run a loco backwards (like ABA diesel operation, you need to find the polarity reverse switch on the loco)
  • Make sure you know your TIU number. When you power the TIU on, a red led comes on, and it a short bit, it will "blink" your TIU number, from 1 to 5. The best practice is to set your TIU to number 1. People have reported strange issues when the only TIU is set to a different unit number. 

Special notes on the VARIABLE 1 input:

  • You can not use the VARIABLE 1 input to power the Track Interface Unit, you can only power the TIU from fixed 1 or the aux pwr jack. You can run an engine from variable 1 if you also have power into fixed 1 or the aux pwr jack.
  • The TIU would pass power through Variable 1 but if fixed 1 or the aux pwr jack was not powered, the TIU would itself be unpowered.
  • This may explain when some people have difficulty because they try to power through the VARIABLE 1 input, but can not find the engine using the remote, and that it takes off on its own. (there is no DCS signal)

Power input and conditioning

Most advanced/experienced users use well filtered DC power supplies. It does not seem that regulation is necessary. (Since the DCS system senses real motor rpm, then it can  "automatically" adapt to changing track voltages)

The DCS signal is, however, very susceptible to noise, more so than DCC, so many users use a rudimentary filter to help clean up the inevitable noise generated by the wiring of a layout. Many users put a small light bulb across the TIU output. If you are running 24 volts or less at the output of the TIU, a 28 volt lamp works fine.

One lamp that has been recommended is from Radio Shack, part number 272-1119, rated at 40 millamps at 28 volts. (This matches the specs for a #1819 lamp.

Another recommended bulb is an automotive #1873, rated at 200 milliamps at 28 volts.

It seems that a wide range of bulbs will work here. The "trick" that most people do not reailze is that the filament of the bulb is a tiny coil, i.e. an inductor, besides a current "drain". The inductive part can help filter noise from the signal. I also suspect that the constant load on the output may help somewhat, but that does not make much sense, since the load from a loco is far greater.



As with any troubleshooting, try to eliminate variables, if you are having trouble and you do not know if it's the radio connection or something else, then "hardwire" the throttle to the TIU, for example. When doing this, be sure that your cable has 4 wires in it. Since this cable has the same connectors as a telephone handset, which only needs 2 wires, this is a common mistake.

Do not rely on the internal TIU fuses for protection. Apparently MTH uses 20 amp fuses internally, but each TIU output seems to be only capable of 12 amps. Try 10 amp fuses. (These last tips courtesy of Gregg Clemmens).

First make sure everything is communicating. Try hitting Read, and you should get "1 TIU found". When you connect a TIU to power, there is a led inside that blinks to represent it's address, 2 blinks is address 2. By seeing this address, you should be able to add the TIU to the system if it is not already added.

Problems adding a loco:

Make sure you have power to the track first, and your TIU is responding (see TIU section)

If you cannot add a loco, make sure it runs on DC first.

Now try to add the loco with the throttle in the forward direction. If that does not work, turn the loco around on the track and try again.

If that does not work, set the throttle to the reverse direction, and try to add the loco on the track and turned around again.

More "gotcha's:

Loose radio board: these are held in with a piece of double sided foam. The adhesive goes bad after a while and your radio comes partially unplugged. Don't drop your TIU, that's almost sure to dislodge the radio. Not very smart design, one screw would have made a big difference.

Apparently when upgrading firmware in the TIU, you need to make sure the audio cables are unplugged inside. I don't have any more info, but intend to research this and take pictures. Several people have commented these need to be disconnected.

When upgrading firmware in the remote, it tells you to hold down a button. Be sure to keep holding it firmly and not release it at all, or you repeat the update cycle all over again.... hold it down!

The 4 pin cable, when used MUST have all 4 pins wired. In addition, the wiring is not straight through, but reversed between the 2 4 pin modular connectors. pin1 goes to pin 4, pin 2  goes to pin 3, pin 3 goes to pin 2, and pin 4 goes to pin 1.

MANY cables are straight through. 

Also, when using a cable instead of wireless, there are 2 telephone style connectors, do NOT use the AIU port! The port should say "remote input".

Make sure that the cable connecting the TIU to the PC is a "straight through" cable, not a null modem cable or the MTH cable used to connect the TIU to a TMCC Command Base. Check for bent pins at both ends of the cable.

Make sure that the 1/8" jumper cable is stereo, not mono.

When updating, is seems that the software is not compatible with Vista 64 bit. I have heard that the loader program won't work. 

Some excellent troubleshooting info from Raymond re: a triplex that blows a 5 amp fuse on the rails

If you have a 2 or 3 amp fuse switch to those for now till you figure this out.   FYI the tender pickups need power for the tender motor, lights, etc to operate (it does sound though like you're getting power to it).  

You can do a couple of things to maybe isolate this some however... disconnect the tender and remove from the track (leave just the engine).  Try to power up and add to remote.  Try startup, running it and different functions.  If that works, then remove the engine and I'd do some checking on the tender...  Use a voltmeter to do a continuity check to see if you have continuity between either power pickup slider and the tender frame. (this is something you don't want to see) (rub a bit of paint off to make contact with the frame metal.)  I would then ensure you have proper continuity between the wheel power pickups on the tender and the tender sliders(same side).  (make sure they arent' wired backwards).  If that tests out ok, I'd probably open up the tender to make sure you don't see any pinched/shorted wires. 

I would take the time to inspect the TO-220 [package] components on the tender slave board to ensure they are electricaly isolated from the metal support frame (do a continuity check) 

Take a look at the wheel power pickup(s) to ensure they aren't shorted internally or have some other sort of issue.(remote and do a continuity check between the two carbon brushes) 

If that all checks out, put the tender on the track and apply power to see what happens, you should get no response and of course the fuse shouldn't blow.  If the fuse blows then you may have something wrong with the slave board and will need to contact MTH.  If it seems ok, then try to connect to the engine.  If the fuse blows again then you may two wires shorted in the tender tether or in the engine.  Also inspect the tender plug on the back of the engine to ensure no pins are bent.


It looks like the latest version, ProtoSound III, has SOME DCC compatibility. There is very limited information, and some things don't work very well, but a step in the right direction.

Here's some limited data which I have not checked out personally yet.

1. ACC and DEC rate values are backwards of most decoders - lower # = more momentum.

2. ALL programming MUST be done on the main - Even systems with a programming track booster don't work with MTH engines. If your system doesn't allow programming the address on the main MTH allows you to program the address using CV's 49,50 and 51.

3. Speed maps are not adjustable - one speed step equals 1 SMPH

4. Function mapping is not supported

5. Advanced consisting is not supported, in fact simple consisting is also a pain, because you can't disable individual functions, like rear coupler, or bell/whistle of trailing loco.

There are MANY more features that can be programmed with function keys, including volume. The volume adjustment cycles up from "sounds off" through "max volume" with nine presses of the appropriate function keys.
MTH engines support up to F28. Pretty much every major feature of DCS is accessible through the function keys.
The only things that are missing are some of the features that require two-way communication, such as measuring a route. You cannot remap the speed curve to match other engines, but you can use the MTH engine as a tool to program other DCC engines to run in SMPH increments. Once you program another manufacture's engine to match SMPH you can consist the engines with a brute force consist, but not an advanced consist.
MTH has acknowledged the need to add advanced consisting and function mapping but those did not not make it into the current ProtoSound II boards.
MTH is working on a gen3 board for HO that will be offered in upgrade kits. That board will support advanced consisting, function mapping, and even BEMF for those who can't or don't want to install an optical reader. The BEMF will give you control in SMPH but the level of repeatability is not as precise as the optical system.
What MTH has to say:

So, my start at the CV's you can access:

supported: ( I heard there were 10 CVs that work, so I need to verify the following)

  • CV1 - primary address
  • CV2 - vstart
  • CV3 - acceleration - NOTE: higher value is less acceleration, backwards from NMRA, enter 1 for maximum
  • CV4 - deceleration - NOTE: higher value is less deceleration, backwards from NMRA, enter 1 for maximum
  • CV5 - vhigh (not sure of this)
  • CV17 - 17 & 18 do long address
  • CV18 - see CV17
  • CV29 - short or long address works - when you set to 128 speed steps, then one speed step equals one SMPH, like under DCS.

 non-supported worth mentioning:

  • CV19 - no advanced consisting


  • (F0) Headlight on/off
  • (F1) Bell on/off
  • (F2) Whistle/Horn on/off
  • (F3) Start-up/Shut-down
  • (F4) PFA initiate and advance
  • (F5) Cab Light on/off
  • (F6) Engine Sounds on/off
  • (F7) Volume low, med, high, off
  • (F8) Smoke on/off
  • (F9) Forward Signal Sound
  • (F10) Reverse Signal Sound
  • (F11) Coupler Slack Sound
  • (F12) One-Shot Doppler on/off
  • (F13) Extended Start Up
  • (F14) Extended Shut Down
  • (F15) Labor Chuff
  • (F16) Drift Chuff
  • (F17) Smoke Volume low, med, high
  • (F18) Single short whistle toot
  • (F19) Coupler Close
  • (F20) Feature Reset
  • (F21) Idle Sequence 1
  • (F22) Idle Sequence 2
  • (F23) Idle Sequence 3
  • (F24) Idle Sequence 4
  • (F25) Brakes auto/off
  • (F26) Cab Chatter auto/off
  • (F27) Clickety-Clack auto/off
  • (F28) Train Wreck
  • Proto-Sound 3.0 With The Digital Command System Featuring: Quillable Whistle With Freight Yard Proto-Effects

Where to get additional help

The best place for tips (and he does custom installations) is Raymond Manley's excellent web site:

be sure to visit the "Tips & Operating help" section.

Here's an O gauge forum, but very helpful: 

Some links on DCS patents, courtesy of Steve C. on MLS: