Decoding the ProtoThrottle Notch Settings

One of the key distinguishing characteristics of the ProtoThrottle Realistic Control Stand Throttle is its throttle handle with eight notches plus idle.  With those characteristics detents, you can operate your locomotives like the prototype and have the prime mover sounds respond accordingly.  Setting this up on the ProtoThrottle is simple and takes just a few minutes, with the help of the ProtoThrottle, to find where your particular DCC decoder transitions between notches.  Those transitions can then be used to pick the optimal speed steps to assign to each notch.

To begin, we need to find at what speed steps the decoder transitions from one notch to another.  The Idle to Notch 1 transition can be tricky since, on the prototype, the prime mover actually stays in Idle when the throttle is in Notch 1.  The only difference is that the field is applied to the traction motors in Notch 1, but not applied in Idle.  For DCC decoders that handle this correctly (Tsunami2 with True-Idle enabled and Loksound, for example), the locomotive will start moving in speed step 1, but the prime mover will remain in idle.

Therefore, the place to start looking is for the Notch 1 to Notch 2 transition.  To do this, go to the ProtoThrottle NOTCH CFG menu.  Select Notch 1 on the menu and set its speed step to 1.  Before going any further, make sure either the brake is engaged or Drive Hold, in the case of Loksound decoders, is enabled.  This will keep the locomotive in the same place for these tests.  (You could forgo this step, but then you’ll have to chase the locomotive around the layout.)  Next, set the reverser to either forward or reverse and put the throttle in Notch 1.  Assuming your decoder follows the prototype, the prime mover sound won’t change.  Begin increasing the speed step value, listening carefully for when the prime mover sound changes.  Make note of this speed step value as the first speed step of the Notch 2 prime mover sound.

At this point, it’s also a good idea to back down one speed step and make sure the prime mover drops back to idle.  If you moved speed steps too quickly, it’s possible the actual transition took place at an earlier speed step.  By toggling up and down over the expected speed steps, you can verify where the transition actually takes place.

Continue increasing the speed step value and repeat the process above until you have found all the transitions between notches.  By keeping the throttle in Notch 1 and changing the Notch 1 speed step value, you can find everything needed simply by adjusting one value.  The video below goes through the whole process using an Athearn GP38-2 equipped with a Soundtraxx Tsunami2 (v1.2) decoder with True-Idle enabled.

From this process, the speed step ranges found for this Tsunami2 decoder are:

Notch 1: 1-14
Notch 2: 15-29
Notch 3: 30-44
Notch 4: 45-59
Notch 5: 60-74
Notch 6: 75-89
Notch 7: 90-104
Notch 8: 105-126

The next step is to configure the ProtoThrottle to use the appropriate speed step in each notch.  Again, using the NOTCH CFG menu, go through each of the eight notches and set its speed step based on the data you found above.  For this example, we’re going to start with a value in the middle of each range:

Notch 1: 7
Notch 2: 22
Notch 3: 37
Notch 4: 52
Notch 5: 67
Notch 6: 82
Notch 7: 97
Notch 8: 112

After configuring the ProtoThrottle, test each notch to make sure you hear the correct prime mover sound in each one.  As before, it may be easier to engage the brake (or Drive Hold) during this test:

Finally, we’re going to take our locomotive out for a spin!  OK, it’s a short spin because my test track is only 4ft long…  Notice in the video how the locomotive starts moving but the prime mover remains in idle, just like the prototype:

After your test run, you may want to go back and tweak the speed step settings for some (or all) notches.  If you want the locomotive to be going faster in a particular notch, pick a speed step near the top of the range for that notch.  Slower?  Pick a speed step near the bottom of the range.  Just keep in mind that the speed step must remain in the range found above for a particular notch in order to get that sound from the prime mover.  If you find the locomotive is still going too fast or too slow, then you’ll need to start changing some other settings in the decoder.  For instance, in a Tsunami2 decoder, CV114 allows you to set the number of speed steps per notch (the locomotive in this example was set to 15 steps/notch).  CV116 serves the same purpose in an original Tsunami decoder.  In other decoders, you may have to modify the speed curve settings, but that’s a topic for another day.

Now that your ProtoThrottle has been properly configured to match your DCC decoder’s prime mover notching, you can sit back and enjoy your investment that much more!


  1. I have an ESU LokSound Select decoder. Is it possible to configure it with the PT to stay in the “idle” sound in Notch 1 and still have it move? You described that and I want to do that, and you mentioned that Loksound is a decoder that handles this correctly – but you didn’t mention if there was any restriction. ANYway, any help/response would be much appreciated – thanks so much for such a great product!

    1. The idle sound in Notch 1 is a function of the sound project in the Loksound decoder. If the sound project implements this correctly, then you’ll get the effect you want – no other configuration necessary. On a Tsunami2 decoder, this behavior is controlled by enabling the True Idle setting.

  2. What if you’re using a 28 step speed table, but only using steps 1-24, so you can set a Tsunami decoder to “3-steps” between notches?

    1. The ProtoThrottle causes a 128-speed step command to be generated by the command station. The Tsunami decoder will respond to that in 128-speed step mode, so the notch settings should always be set based on a 128-speed step table. Although other settings in the decoder may be done in terms of 28-speed steps, the decoder should respond to any 128-speed step command in kind:

      “A compatible multifunction decoder switches to 128 speed step mode automatically at the track level when it receives a 128-speed step command from the command station. The decoder will revert to 28 speed step mode when it receives a command in that speed step format. Unlike 14 and 28 speed step commands, it does not need to pre-programmed to enable 128 speed step mode operation. It is always on, ready to be used at any time.”

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