Digitrax DT100R Throttle Operating Instructions

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Digitrax DT100R Throttle Operating Instructions

Notice: The DT100 and DT100R Throttles have been discontinued by Digitrax since 2000, and parts are no longer available from Digitrax as of January 2006. DT100 and DT100R throttles sent to Digitrax for repair will be returned to the owner. Please refer to the section on "Maintenance" below for assistance in solving problems with the DT100 and DT100R throttles.

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Table of Contents

DT100R Operating Instructions

  DT100R Description

  Setting Up the DT100R

  DT100R Tetherless Operation

  Train Operation with the DT100R

  Turnout Operation with DT100R

  Program Decoders with DT100R

  Maintenance & Troubleshooting


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Click on title for desired topic.



The North Raleigh Model Railroad Club (NRMRC) has adopted the Digitrax Chief as the foundation for the Club's Digital Command Control system. The Club decided it would purchase needed Command Stations, Power Boosters, Power Managers and Radio Receivers, while individual Members would purchase radio throttles. This method was chosen to make individuals responsible for their own throttles, including maintenance and repair, and was based on previous experience with club-owned radios.

Many members do not have home layouts and thus do not own complete Digitrax DCC systems. The manual provided by Digitrax with DT100R throttles purchased separately covers only those radio functions of the DT100R. The bulk of information on the DT100 family of throttles is in the Chief Manual, which these Members do not have. This page has been created to combine information on the DT100R throttle from both of these plus other sources, and provide comprehensive information on how to setup, use and maintain the DT100R throttle. Click here for a shorter summary showing only the operational and programming instructions.

The best way to learn and remember how to operate a DT100R throttle is to actually do it. Do each step as you read it. Repeat for different locomotives. Soon you will remember the most commonly used functions, and they will become second nature. For the others come back to this page as needed.

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Description of the DT100R Throttle

Dt100 ThrottleThe Digitrax DT100R throttle is essentially a DT100 throttle that contains a simplex (one-way) transmitter that uses its cable (LocoNet) connection to establish initial locomotive address selection and other related functions. After a DT100R has selected a locomotive and/or established a MU consist, it may then be untethered and will automatically switch to radio operation for all subsequent speed, direction and function commands. In the tethered mode the DT100R behaves exactly as a regular DT100 with exactly the same features and capabilities.

The DT100R throttle uses a combination of color-coding, LED indicators, a LCD display and multi-function buttons to accomplish a wide range of capabilities in a compact and light-weight case that is easily held in the hand. The 6-wire flat cable with RJ12 plug extending out from the throttle is for connecting to LocoNet only. The antenna for the radio transmitter is entirely within the throttle case.

Control Panel Description

Color Codes
Color coding is used on the DT100R control panel to indicate how the keys are used. GREEN buttons and indicators handle locomotive speed and direction control. The RED button is RunC, RUN/STOP. It is the only button that is red and is so color coded for emergencies. BLUE buttons handle function control. When the function mode is active the GREEN buttons on the bottom row take on the BLUE meanings F3/F7, F1/F5, F2/F6 and F4/F8, in left-to-right order.

Left and Right Throttle Knobs
The throttle knobs on the DT100R are encoders, not rheostats (variable resistors), and give very smooth, fine speed control. They can be turned continuously; there is no left and right stop points as with a variable resistor. In the 128 speed step mode it can take several turns of the knob to go from stop to full speed.

The tracking characteristics of the knobs can be customized for either "straight line" or "ballistic" tracking. With straight line tracking each movement of the knob causes a fixed rate of change in the display. With ballistic tracking, the faster you move the throttle knob, the faster the data changes in the throttle. Ballistic tracking is the default setting, but it can be changed as described under Setup. For wireless use, it is recommended you change to Straight Line tracking.

Direction Indicators
These are the LEDs located above and to the center of the case next to each throttle knob, with the symbol KeyDirC. They have the following meanings:


Locomotive is running in reverse.


Locomotive is running forward.


Throttle is active in the LCD display

Both flashing ORANGE

System is in "stop" mode with track power ON.

Both solid ORANGE

System track power is OFF.

Program Mode Indicator (PROG)
Located to the lower left of the right throttle knob. This LED indicates this DT100R throttle is in the programming mode. In this mode the throttle knobs do not control any selected locomotives, but permit the use of the Service Mode programmer in the Command Station or perform Operations Mode programming on the mainline. See section on Programming.

Address Mode Indicator (EXP)
This LED indicates whether the active throttle knob is controlling a 2-digit short address, a 4-digit aliased address or a 4-digit long address, as follows:


The display active throttle in the DT100R is controlling a 2-digit short address.

Blinking RED

The display active throttle is controlling an 4-digit address that is aliased to a 2-digit address decoder.

Steady RED

The display active throttle is controlling a 4-digit long address.

Note: The North Raleigh Model Railroad Club strongly recommends against use of alias addresses, especially at Train Shows. Further information on alias addressing is excluded from these descriptions.

Any two of 2-digit, 4-digit and/or alias addresses can be mixed on the same throttle.

The LCD Display
The DT100R display is a single line LCD display used to display several different types of information.

The three small mode indications across the top of the LCD define the current operational state of the DT100R, and indicate whether you are in MU ModeMU (multiple unit or consist mode), LOCO ModeLoco (regular locomotive operations mode) or SWITCH ModeSwitch (turnout control mode) mode. Only one of the indicators will be lit at any time. The DT100R defaults to the LOCO mode and returns to this mode if you change to another operational mode and don't do anything within about 6 seconds. Use the KeyModeC button to toggle among these operational modes.

The numbers and letters in the LCD display have different meanings depending on the current DT100R mode and the functions being executed, and they may be flashing or not. A flashing display is usually a prompt. All displays and meanings are described on this web page.

The colon : in the middle of the display is flashing when the Fast Clock is being displayed. There is no colon : displayed when working with 4-digit addresses and a steady colon : will be displayed when working with 2-digit addresses and when status editing.

DT100R Throttle Control Buttons


This button when used by itself can operate in one of two ways, as defined by the options set when the DT100R is powered up. The setting of these options is defined later.

  • The default Local Run/Stop controls only the addresses under control of the throttle when the KeyRunC button alone is pressed for 1 second. Press again to toggle between STOP and RUN.

  • Global Run/Stop controls the entire layout when the KeyRunC button alone is pressed for 1 second. Press again to toggle between STOP and RUN.

There are other uses for Run/Stop in conjunction with other buttons as described elsewhere on this page.


This button is used for selecting and setting locomotive addresses to the throttle. When the DT100R is address selecting or in "browse" mode the LOCO mode display indicator will be blinking. If there is a steady 4 digits and no colon : in the display, a 4-digit address is being selected. The EXP indicator will also be lit and indicates which type of 4-digit address is being selected (steady EXP means 4-digit long addressing and blinking EXP means aliased 4-digit address).

If the left 2 digits and the LOCO mode indicator are flashing, and there is a colon : in the middle of the display then a 2-digit short address is being browsed.

This button is also used in other modes to select or complete an operation, as described elsewhere on this page.


Mode: Press the KeyModeC button to move from one operational mode to another. LOCO is the default mode since most of the time the throttle is controlling locomotives. Press the KeyModeC button to change to SWITCH then to MU then back to LOCO.

Dispatch: To Dispatch or offer a locomotive set up on the DT100R to another throttle, press the KeyModeC button while in Select Address Mode.

Display: In programming mode this button is used to read back or DISPlay a CV value from a decoder on a DCS100/DCS200 Command Station's Service Mode programming track. (Note: this button does not work for this function with a DB150 Command Station.)

Function/F0/Light Control

Press the KeyFuncC button once to enter Function mode. The display will show Fn:oo with the oo flashing to indicate you must choose which function you wish to toggle. Press KeyFuncC again to toggle the directional lights on (Fn:on) or off (Fn:of). Or press the buttons above F1, F2, F3 or F4 to toggle any of those functions that are available in the locomotive. Function 2 (F2) is a special button because it is non latching; this allows activating a function while the button is held down and deactivating when the button is released, such as blowing a locomotive horn.

Press and hold the KeyFuncC button while pressing the buttons above F5, F6, F7 and F8 to toggle functions 5 - 8 on and off.

In Edit and Programming modes the KeyFuncC button is also used to cycle among several choices.

Function 1 - 8 Buttons
These buttons are active while in Function mode. The buttons above the F designations can be used to access various decoder functions. F2 is non latching.

Left and Right Direction Change Arrows
KeyDirLtC and KeyDircRC

These buttons change the direction of the locomotive(s) on the related throttle knob. The KeyDirLtC button changes direction of the address on the left "L" throttle knob, and the KeyDircRC button changes the direction of the address on the right "R" throttle knob.

These buttons are also used to select the position to which a turnout or switch is to be set:

KeyDirLtC t = thrown      KeyDircRC c = closed

These buttons are also used by various system editors to control data entries.

Up/Add and Down/Delete Arrows
KeyUpC and KeyDownC

These buttons are used to browse addresses and to increase/decrease speed. They are also used to MU-link and MU-unlink locomotives from consists. These buttons are also used by various system editors.

These +/- buttons can be configured to be repeating so that holding down a button will cause it to repeat itself until the button is released. This is the normal default when "ballistic mode" is selected in the Option setup for the throttle.



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Initial Setup with the DT100R Throttle

DT100R Throttle Configuration Options

The DT100R throttle has an individual throttle OPTION mode that is used to customize the throttle. The options are assigned as hexadecimal numbers representing combinations of options as shown in the following tables. The default values, shown in bold are generally satisfactory for most operations, however it is recommended for radio operations that ballistic tracking be turned off by setting the Primary Option value to 00.

It is strongly recommended that all locomotives assigned to the throttle (both throttle knobs) be released (i.e. dispatched) before any options are changed.

DT100R Primary Options

DT100R Secondary Options


Options Enabled


Fast Clock

Key & Knob


















































































Bottom Digit
Secondary Option Value

Throttle Default for NEW
Decoder Type


28 step decoder


Motorola Trinary decoder


14 Step decoder


128 step decoder


28 step FX decoder


128 step FX decoder


Disable NEW type override feature

Top Digit Secondary
Option Value

Tetherless Features Control


Normal radio mode with Power Saver


Turn off radio capability - act like DT100


Normal radio mode without Power Saver

Changing DT100R Configuration Options
To change DT100R configuration options be sure the throttle has a good battery installed and then proceed as follows:

Unplug the DT100R from LocoNet, if connected. Press and hold the KeySelC button and plug the DT100R into LocoNet. Alternatively you can press the KeyRunC, KeyModeC and KeyUpC buttons simultaneously to reset the throttle. The display will show the Primary Throttle Option Screen oP:01 (default). This display will appear for approximately 5 seconds. If no action is taken during the 5 seconds the DT100R will enter RUN mode.

While oP:nn is still in the display, use either throttle knob to modify the Primary option value according to the Primary option table above.

Save the primary throttle option code by pressing the KeySelC button. The display will then show the Secondary option screen oS:03 (default). The secondary option screen oS:03 (default) will appear for approximately 5 seconds. If no action is taken within 5 seconds, the DT100R will return to RUN mode.

While oS:03 is still in the display, use either throttle knob to modify the Secondary option value according to the Secondary option table above. The Secondary option codes shown allow the system default NEW decoder type when selected with this DT100R to be overridden.

To save the secondary option code press the KeySelC button. The throttle will next show the throttle ID number. Make sure the ID is unique to the throttles used on this system. Use either throttle knob to modify the ID value. Press the KeySelC button to save the ID code.

Finally, the display will show the Radio Frequency channel rf:00 (default). This sets the channel for radio operation. This should virtually never need to be changed.

Note: If no keys are pressed, the time-out for Throttle Option Mode is 12 seconds and the DT100R will go to idLE if no button is pressed within that amount of time.

DT100R Major System Modes and System Startup



DT100R Power Up/Option Set Up

Install 9V battery or plug throttle into active LocoNet.

The DT100R beeps and displays ID code. Press KeySelC twice to bypass ID and option codes. Later versions of the DT100R do not show the ID and option codes but go directly to the idle display. To access the throttle options with this version, reset the throttle as described below for DT100R unit reset.

Plug the DT100R into LocoNet. The DT100R will beep and the LCD display changes from Idle. If the Command Station is not supplying power to the rails, the DT100R's direction indicators will be steady ORANGE and the Command Station Track Status indicator will be off.

Track Power On/Off Mode

If track power is off, press the KeyRunC and KeyUpC buttons simultaneously to turn all track power on.

If track power is on, press the KeyRunC and KeyDownC buttons simultaneously to turn all track power off.

Run/Stop Mode

Whenever the DT100R's direction indicators are flashing ORANGE, the layout is in STOP mode.

To change to RUN mode press the KeyRunC and KeyUpC buttons simultaneously. The direction indicators will show the direction of the decoder assigned to the adjacent throttle knob, either RED, GREEN or OFF.

To change to STOP mode press the KeyRunC and KeyDownC buttons simultaneously for about a second, until the direction indicators start flashing ORANGE. Note there is power to the track, but all locomotives are stopped.

Programming Mode

Press the KeyRunC and KeyFuncC buttons simultaneously to enter programming mode. Decoders can then be programmed as described in the Programming section.

DT100R Unit Reset

Press the KeyRunC, KeyModeC and KeyUpC buttons simultaneously. This will force the DT100R to reset. First release any addresses being controlled by the throttle.

DT100R Fast Clock

DT100 family throttles in conjunction with the DCS100 and DCS200 Command Stations offer a networked fast clock on the all the DT100's in the LocoNet system. The fast clock display is a 4-digit 24-hour format clock with the colon : blinking. The DT100R can be set so its default display is either the fast clock or the LOCO mode display — when there is no activity on the DT100R for about 6 seconds, the display reverts to the default display set up in the DT100R. Turning a knob or pressing any button will cause the display to change to reflect the current throttle activity. LOCO mode is the default display for the DT100R — see Changing DT100R Configuration Options above in this section for changing this default display to the fast clock.

When a DT100R is plugged into LocoNet the system will update its fast clock time and rate so it is synchronized to the rest of the system.

Each DT100R throttle can be set up with its own alarm. When the fast clock time matches the private alarm time set the DT100R will beep and flash up the message ALAr to indicate the alarm time has elapsed. The alarm time uses the 24-hour time format.

The fast clock rate is user selectable from 1:1 to 100:1 in steps of 1. Setting the clock rate to 00 will stop the fast clock in the whole system at the currently displayed time. To re-start, set the clock rate to a non-zero value.

The fast clock functions are set and modified as follows:



Set Fast Clock Time, Rate and Alarm

From LOCO mode press the KeyModeC button to change to SWITCH mode.

Press the KeyFuncC button to change from SWITCH mode to EDITOR modes. If routes are enabled in the system press the KeyFuncC button a second time to change from the Route Edit mode to the Fast Clock Edit mode. The display will flash cLoc to show it has entered the clock editor.

To set the clock, use the left throttle knob to change hours and the right throttle knob to change minutes. When the desired time shows in the display press the KeySelC button to set this time in the whole system. If this button is not pressed for approximately 6 seconds the fast clock will not be synchronized, the DT100R will re-synchronize to the existing system time, and the DT100R will return to LOCO mode.

Clock Rate Editor

After modifying and setting the fast clock time, advance to the rate editor by pressing the KeyFuncC button again. The display will show rAtE on the first screen and then display a second screen showing Fr:xx where xx is the fast rate.

Use either knob or the KeyUpC or KeyDownC buttons to set the fast clock rate desired for the whole system. Press the KeySelC button to update the rate.

Alarm Editor

Next press the KeyFuncC button again to enter the private alarm setting editor for this particular DT100R. The display will show ALAr to indicate it is in Alarm Edit mode.

Use the throttle knobs to set the alarm time in the 24-hour format. Since this time is private to the individual DT100R throttle, there is no need to set it to the system. Either press the KeyFuncC button to exit Edit modes and return to LOCO mode, or let the throttle timeout back to LOCO mode.

Locking the DT100R Throttle

Pressing the KeyUpC and KeyDownC buttons simultaneously will lock the throttle, with the display as Locd. Pressing both buttons again will toggle out of the locked mode and return the throttle to normal. In Locked mode, all of the buttons are rendered inactive.



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Radio (Tetherless) Operation with the DT100R Throttle

The DT100R throttle will operate as a standard DT100 throttle when it is plugged into LocoNet, and as a radio wireless throttle when unplugged from LocoNet and at least one UR91 radio receiver is present. When the DT100R is plugged into a working LocoNet, it will verify that at least one radio capable receiver is present. The DT100R will then assume the current Network ID that the radio receiver(s) are set to, and subsequently allow itself to switch to radio operation when it detects a disconnect from LocoNet.

LocoNet Connection
On connection to a LocoNet that has radio capability, the DT100R LCD display will flash the radio status code rA:0n where the number "n" signifies the LocoNet ID being used by all receivers on the system it is connected to. The display will then switch to normal DT100R tethered operation displays and actions. If the system does not have a UR91 or equivalent device, the DT100R will not display the rA:-- message to show that it cannot operate in radio mode on that system.

Display Power Down
When a DT100R throttle is connected to a LocoNet and received the LocoNet ID number it will allow tetherless operation of locomotives that have been selected into either throttle knob. If an untethered DT100R detects no user throttle activity for about 3 minutes, it will enter Power Saver mode and display r- PS on the display until a throttle or button action restores normal activity and displays. If the DT100R has a locomotive assigned to it and is in Power Saver Mode, it will continue to "check in" with the system every 60 seconds telling the system "I'm still here". This keeps the system from releasing that locomotive back to "common". The direction LED's of active throttles may blink every 1.5 seconds when the DT100R is checking to see if any new key or encoder input has been made. The easiest and fastest way to signal the DT100R to exit from power saver mode is to hold down either the KeyDownC or KeyUpC button.

To force a DT100R to enter the lowest power use idLE state, either connect it to a LocoNet which is in sleep mode, or simultaneously press the KeyRunC KeyModeC and KeyUpC buttons to reset the throttle. Once the DT100R has been reset it remains idLE until it is reconnected to an active LocoNet. You may also simply remove the battery to completely power down an untethered DT100R.

Releasing a Locomotive
When working in the radio mode, pressing the KeySelC button will immediately release the controlled locomotive as common to the system and the throttle will become inactive. To re-select this locomotive, the throttle must be reconnected to LocoNet. The DT100R will automatically reselect that locomotive when plugged in to LocoNet. Due to the close proximity of the KeySelC button to the right throttle knob reverse button, you may wish to assign locomotives to the left throttle knob for normal operation.

Multiple Unit Operations
The DT100R must be connected to LocoNet to either make up or break down consists. Consists may be operated normally with the DT100R tetherless.

The DT100R must be connected to LocoNet to use its Service Mode programming. When tetherless, Operations Mode programming will work normally except that the DT100R will not receive any return or feedback messages.

Switch Mode
Switch Mode works to throw switches and routes normally when the DT100R is tetherless. However, Route Editing requires a connection to LocoNet.

Ballistic Tracking
When operating in the radio mode, throttle knob tracking will feel slightly different than when connected to LocoNet. When in the radio mode, slow movement of the throttle knob will result in improved locomotive response.

Throttle Orientation for Normal Operation
The orientation to hold the DT100R in normal usage is from horizontal to 30° upward in a natural hand position about 12" out from your body. This gives the best radio coverage. Note that occasionally wiring, metal plumbing, HVAC ducting and other items may cause small areas of poor reception around the layout. Moving about 6" - 24" in any direction or varying the orientation of the DT100R will typically overcome any dropouts.

Fast Clock (Chief only)
When the Fast Clock option is being used, the DT100R keeps track of and displays Fast Time based on what the Fast Time was the last time the DT100R was connected to LocoNet. If Fast Time changes (someone edits it) while tetherless, the DT100R will see the change only when it is plugged into LocoNet at which time its display will be updated.

Battery "Fuel Gauge"
The DT100R continually checks the voltage of its battery while running tetherless. If it detects a low voltage it will beep twice within a second and display bt:nn on the display. The n is the number of times the warning has sounded. The warning will continue every 5 minutes until the battery is changed. Don't panic when this warning appears, as the throttle unit will continue to operate normally for an extended time. A prudent action would be to change the battery as soon as reasonably possible — the battery can be "hot changed" while the DT100R is plugged into LocoNet.

LocoNet ID Change
Normally, a DT100R accepts and uses the LocoNet ID offered by the compatible radio receivers it sees when connected to LocoNet. The DT100R may be used to change LocoNet to a different ID (for example, to allow for 2 clubs at the same train show). To do this use the following procedure:

Disconnect a DT100R with a battery in it from the LocoNet for which the ID will be changed.

Press and hold down the KeyModeC button on the DT100R and then re-connect the throttle to LocoNet.

Release the KeyModeC button. The DT100R will flash up the current radio status rA:0n where the n shows the current LocoNet ID. Use the right hand throttle knob to change the ID digit n to that desired, in the range 0 to 7, and then press the KeySelC button to set the system to the new ID.

Reconnect any DT100R to be used on this system to LocoNet so it can adopt the new ID number.



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Train Operations with the DT100R Throttle

LOCO mode is the default mode for the DT100R since this mode runs the trains. If you change to SWITCH or MU mode and don't do anything, the throttle will switch back to the default LOCO mode in about 6 seconds.

Digitrax Command Stations (DCS050, DCS100, DCS200, DB150) have a decoder address range from 01 to 9980, plus address 00 for analog locomotives. The address range is broken down as follows:

Address in Display

EXP Indicator


0001 to 9980

RED Flashing

Alias Roster for Aliased Addresses



Analog Address

01: to c7: (note)


2 Digit Short Address range

0128 to 9980

RED Steady

4 Digit Long Address range


Digitrax Command Stations utilize Mixed Mode hexadecimal addressing for addresses from 100 to 128. Mixed Mode addresses are considered as 2 Digit Short Addresses for programming purposes. The conversion from decimal to Mixed Mode addresses is shown in the following table.


Mixed Mode























Mixed Mode























Mixed Mode

















The following table provides the information needed to select locomotives and operate trains using the DT100R throttle. Note: since the North Raleigh Model Railroad Club does not recommend using aliased addresses, detailed information on aliases and alias addressing is not provided. The topic of Advanced Consisting will be added at a later date.



Select Locomotive to Drive

The DT100R must be connected to LocoNet to perform this function.

Turn desired throttle knob at least 1/8 turn in either direction until the display shows SE:L-. If SE:L- does not appear, the throttle knob may already be assigned to a locomotive. The first time a locomotive is programmed to a throttle on the system it is set to the throttle knob at speed 0, forward direction and all functions off. The only way to control consisted or MU'd locomotives is to select the address of the TOP of the consist.

If you try to access a locomotive address that is active on another throttle, when you press KeySelC to set the address, the display will change back to SE:L- and the throttle direction indicator KeyDirC will not light.

To select a 2-Digit Short Address, press the KeySelC button — the display shows 00:03 with the "00" flashing. Turn either throttle knob until the desired locomotive's address appears on the display. You may also use the KeyUpC or KeyDownC buttons to browse to the desired address. Press KeySelC to set this address active.

To select a 4-Digit Long Address, press and hold the keySelC button then turn one of the throttle knobs. The DT100R enters the 4-digit long address range, and the RED EXP indicator lights. Browse for the 4-digit address you wish to select (left throttle knob changes in hundreds, right knob in ones). Press KeySelC to set this address active.

If during the address select process there is no input for the 6 second time-out period, the DT100R will abort the selection process and restore back to LOCO mode.

If the right hand side of the display shows FF during address selection it means the Command Station has reached the limit of its internal slot memory. If this occurs you can free up some slots by making sure any locomotives not being used are not selected on any throttle. Depending on the Command Station (DCS100, DCS200) it may be possible to increase the capacity of slot memory. Refer to the Digitrax System manual.

Forced Selection — Stealing a Locomotive

Except where instructed below, the DT100R must be connected to LocoNet to perform this function. The throttle must have a good 9 volt battery installed.

Normally a locomotive cannot be selected if it is already assigned to a throttle. It is possible to override this interlock and force the DT100R to select an in-use locomotive. To "steal" a locomotive, do the following:

  • In the same way you would select a locomotive to drive, browse to the address of the locomotive you want to steal. With a 2-digit address the right side of the LCD display should typically show 3x. With a 4-digit address the locomotive status will flash up St:3y.

  • Before you timeout from browse mode and while you still have the desired locomotive showing in the display press the KeySelC button. (If the locomotive is not available for any reason, the display will show SE:L-.)

  • Disconnect the DT100R from LocoNet. The display should immediately go to idle.

  • Press and hold the direction arrow button for the throttle side (either KeyDircRC or KeyDirLtC) you used above and plug the DT100R back into LocoNet. After the DT100R beeps release the direction button and the throttle being used should be logged onto the stolen locomotive address.

If the locomotive is active on two throttles, both throttles can update speed and direction information for the address.

Controlling Lights and Functions

Press the KeyFuncC button once to enter the Light/Function control mode for the "display active" throttle. The display will show Fn:oo with the n flashing to indicate that the function number of the function you wish to change needs to be selected.

Use one of the five BLUE buttons to choose the function you want to change. The KeyFuncC button will now select and change the Light or F0 function. Each time the KeyFuncC button is pressed while in the Fn:oo mode, the Light/F0 will change from OFF to ON and vice-versa. The display will show F0:on (Function 0:on) for light ON and F0:of (Function 0:off) for light OFF. The operation is the same for the other functions F1, F2, F3 and F4.

To access functions F5 through F8, press and hold the KeyFuncC button while pressing the BLUE F5, F6, F7 or F8 buttons to toggle between on and off for the function chosen.

You can change any or all of the functions F0 – F8 while you are in the Fn:oo mode.

There are three options to return to LOCO mode:

  • Adjust either throttle knob

  • Press the KeyModeC or KeySelC buttons, or

  • Wait for the 6 second no-input time-out to elapse.

F2 is a non-latching function, which aids in controlling sound features such as a horn or whistle. The function operates only when F2 is held down in the Fn:oo mode.

Even though a locomotive is part of a consist, its functions can still be accessed independently. Select the desired locomotive address in the normal manner. After the KeySelC button is pressed the display will show cn (aa:cn for 2-digit address; -cn- for 4-digit address). Press the KeyFuncC button and proceed with the normal function controls described above.

Set Up Multiple Unit Operation

The DT100R must be connected to LocoNet to perform this function.

The TOP locomotive is the locomotive on the DT100R right throttle, and is the controlling locomotive. Other locomotives in the consist are added from the left throttle to the TOP locomotive, each in turn.

Set the address and relative direction of the next locomotive using the left throttle, as described in "Select Locomotive to Drive", and place the locomotive in physical position in the MU consist.

Press the KeyModeC button twice to cycle the DT100R through SWITCH mode to MU mode. The MU LED indicator lights.

Press the KeyUpC button to add the locomotive to the TOP locomotive.

It is possible to add a consist to another consist — i.e. nested consists. The TOP of the top consist should be on the right throttle knob. The TOP of the consist to be added should be on the left throttle knob. Add the left consist to the right consist as described above. The overall consist is controlled by the right throttle knob. It can then be released and selected to run from either throttle knob or on another throttle or dispatched to the system.

Remove a Locomotive from a MU Consist

The DT100R must be connected to LocoNet to perform this function.

Select locomotive to be released on the Left throttle. The display will show cn for the locomotive speed.

Press the KeyModeC button twice to get to the MU mode.

Press the KeyDownC button to unlink the locomotive. The unlink is complete, and the left throttle becomes active with the locomotive just unlinked. The unlinked locomotive is broken out of the consist at the current speed and direction it was going in the consist.

To unlink an entire nested consist you must first dial up the TOP of the nested consist onto the left throttle knob. Then unlink it as described above.

Dispatch a Locomotive

Follow the procedure above to select the desired locomotive to drive.

Press KeySelC to enter Address Select on the active throttle.

Press the KeyModeC button once to dispatch the locomotive or MU consist. The locomotive or consist is dispatched in its current state — moving, stopped, etc.

Locomotive Speed and Direction Control

Locomotive Speed Control
Turn the throttle knob that is set to the locomotive whose speed is to be changed. If not already active in the display, the throttle will become "display active" and the display will show the address and current speed. As well as by turning the throttle knob, speed can be changed using the KeyUpC and KeyDownC buttons.

With a 2-digit address the address is shown on the left side of the display with the current speed on the right side, separated by a :. When a 4-digit address is changed the new speed xx will flash up on the display as SP:xx and the display will return to the steady 4-digit address with no colon, and with the LOCO flag on.

The only way to change the speed of consisted or MU'd locomotives is to select the address of the TOP of the consist. When a consisted or MU'ed address other than the top address is selected the display will turn to aa:cn if a 2-digit address aa or to -cn- followed by the 4 digit address if a 4-digit address. This indicates the speed of this address cannot be changed since it is in a consist. Functions such as lights can be modified for such an address.

Locomotive Direction Control
To change a locomotive's direction press the KeyDircRC button for the address set to the Right Throttle Knob or the KeyDir:tC button for the address set to the Left Throttle Knob. The direction indicator beside the throttle knob will change color (to RED for reverse or GREEN for forward). The throttle is/becomes display active.

Changing direction of a moving locomotive will cause it to slow down to 0 speed and then speed up to the commanded speed according to the decoder's programmed deceleration and acceleration characteristics. (Zero deceleration and acceleration settings will result in instant reversal.)

Status Edit a Decoder

The DT100R must be connected to LocoNet to perform this function.

Status editing of a decoder is required when the decoder is not able to operate under the Command Station's normal configuration. To status edit a decoder you must do so after dialing the desired address and before pressing KeySelC to set the decoder to the throttle.

Press KeySelC and turn either throttle knob until the desired address appears on the display. For a 2-digit Short Address, the decoder status will display in the right side of the display aa:xy where x and y are the two digits of the status code. For a 4-digit Long Address or Aliased 4-digit Address the data will be displayed in 2 screens — the first screen is the 4-digit long address for about 1 second, then St:xy which means Status Code = xy.

Press the KeyFuncC button and the status code xy will begin to flash.

Use either throttle knob to change the status value. This value will be displayed in the right hand side (2-digit) of the display or on the second screen (4-digit).

When the desired status code is displayed press KeySelC to change the status code and set it to the display active throttle.

A consisted locomotive address cannot have its status edited. The locomotive must be unlinked from the consist.

You cannot change the value of the x which is set by the system. The values for y are as follows:

Status Digit Value



Normal 28-speed step decoder


Motorola Trinary/AC Digital type decoder


Baseline 14-speed step decoder


Normal 128-speed step decoder


28-speed step FX decoder


128-speed step FX decoder


128-speed step decoder and Consist TOP



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Turnout (Switch) Operations with the DT100R Throttle

Under Construction Sign

This section will be added later.



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Programming Decoders with the DT100R Throttle

The DCS050, DCS100 and DCS200 Command Stations have a built-in Service Mode programmer that lets you read back and write decoders on a separate electrically isolated programming track, which means programming can be carried out at the same time as layout operations. The Service Mode programmer can be accessed by any DT100 family throttle connected to the Command Station.

The DB150 Command Station is also equipped to perform Service Mode programming. However, there is no separate programming track so layout operations must be shut down during programming. You must also be very careful to remove any locomotives not being programmed from the layout, or they will be re-programmed to the same characteristics as the desired locomotive. The programmer in the DB150 is write-only; it does not have the capability to read back the values in the decoder.

The DCS100/DCS200 implement 3 different methods of Service Mode programming as well as Operations Mode programming (which permits changing CV values while a locomotive is on the layout tracks). The 3 types of Service Mode programming (Paged – most common; Physical – least sophisticated; Direct) are defined in NMRA RP-9.2.3, and are provided to ensure the ability to program DCC-compatible decoders from all DCC manufacturers who support this RP.

When the DT100R enters programming mode, the current Programming method it is using is displayed on the LCD screen:


Paged programming (default)


Primitive Physical register programming


Direct Programming


Operations Mode programming on layout tracks to the active throttle's decoder address.

When the DT100R is in programming mode, pushing the KeyModeC button will cycle among the 4 programming modes. When you exit programming, the DT100R retains the last programming mode used as well as the last CV number and its data value. The next time programming mode is entered, you will be at the same place you left off.

Service Mode Programming

The DT100R must be connected to LocoNet to perform this function.



Entering Programming Mode

Press the KeyRunC and KeyFuncC buttons together, until the Programming indicator PROG LED glows GREEN.

Be sure the locomotive to be programmed is on the programming track.

Note that CV01, the locomotive address CV for 2-digit addressing, displays as Ad rather than 01.

Exiting Programming Mode

To return to LOCO mode when finished programming, press the KeyRunC and KeyFuncC buttons simultaneously. The PROG LED will go out.

Programming the Decoder

Turn the Left Hand Throttle Knob "L" until the Configuration Variable (CV) number to be changed is displayed in the left hand side of the LCD screen. When a CV is first accessed, it will display 2 dashes (- -) in the right side of the LCD to signify that the CV contents are unknown. (Note: CV01 will display as "Ad" on the left side of the display.)

Press the KeyModeC button to read the current value programmed for this decoder. As the Command Station is scanning or reading the decoder the left most digit will move in a "pretzel" formation to show activity. When a data value is successfully read, it will display flashing in the two right hand digits.

A read failure will result in one of the following messages:


means the programmer is being accessed by another device. Try again.


means there is no decoder on the programming track, or it has been removed since programming began.


means the decoder is detected, but does not give the correct response.

The CV value can now be modified by turning the Right Hand Throttle Knob "R" until the desired value is showing in the right hand side of the LCD display. Press the KeySelC button to "set" or write the value to the decoder. A successful write will be indicated by a flashing Good on the display. Note: if there is no CV value in the decoder (right digits show dashes) you can force a write by pressing KeySelC twice.

Continue selecting, reading and writing other CV's until you have completed programming them.

To program a 2-digit short decoder address turn the Left Throttle Knob until Ad (CV#01) appears in the display. Press keyModeC to read back the existing address. Use the Right Throttle Knob to change the right side of the LCD screen to the 2-digit address to be set in the decoder. Press KeySelC to write the address. The DT100R will flash Good. Press KeyModeC to read back the address to verify correct programming. Note: for the 2-digit address to be active set CV29 to 06.

To program a 4-digit long decoder address both CV17 and CV18 must be programmed, which the DT100R will do together. Use the Left Throttle Knob to select CV18 in the left two digits of the display. Press KeyModeC to read back the value stored for CV18. When this value appears, press KeyModeC again, which forces the DT100R to read back the complete 4-digit address and display it as a flashing 4-digit number in the display (Lad- will flash during the search). Use both throttle knobs to modify the displayed 4-digit address to the desired address. (The Left Throttle Knob changes in steps of 100, and the Right Throttle Knob changes in steps of 1.) Press the KeySelC button to write the new address. The display will flash GOOD if the programming is successful. Note: for the 4-digit address to be active set CV29 to 26.

A decoder can be programmed with both a 2-digit and a 4-digit address. The active address is determined by the value of CV29.

Note: while it is possible to program a 4-digit address from 100 to 127 into a decoder, a throttle cannot access that address since the throttle uses mixed mode for these addresses, (i.e. from a0 to c7). Use 2-digit mixed-mode addresses for 100-127.

The most commonly used CVs for basic locomotive operations are the following:

CV #

Used For

Value Range

Ad (01)

Locomotive 2-digit short address

01 – 99 decimal, a0 – c7 mixed mode


Locomotive 4-digit long address high

c0 – FF hex


Locomotive 4-digit long address low

0 – FF hex


Configuration Register

See following table

The following table lists some of the common hexadecimal (hex) values used in the Configuration Register CV29 and their meaning:

Value in CV29

Meaning to Decoder

Speed Steps

Address Mode

Analog Conversion


14 (Standard Mode)

2-digit short



28/128 (Advanced Mode)

2-digit short



14 (Standard Mode)

2-digit short



28/128 (Advanced Mode)

2-digit short



Enable Loadable Speed table

2-digit short



14 (Standard Mode)

4-digit long



28/128 (Advanced Mode)

4-digit long



14 (Standard Mode)

4-digit long



28/128 (Advanced Mode)

4-digit long



Enable Loadable Speed Table

4-digit long


Refer to the decoder manual for a list of the CVs covered by the decoder as well as a complete listing of CV29 values.

Operations Mode Programming

Operations Mode programming permits the programming of CVs in FX-decoder equipped locomotives while they are on the layout tracks, rather than requiring them to be on a programming track. Thus the acceleration rate (CV03) and/or the deceleration rate (CV04) of a locomotive can be changed to simulate the weight and braking power of the train to compensate for a changes in the number of cars and locomotive units. The FX parameters CV49 – CV53, and CV62 and CV63 can also be modified using Operations Mode programming.

Operations Mode programming can be performed by any DT100 family throttle at any time since the throttles are not competing for use of the single programming track.

Operations Mode programming can be carried out in radio mode (tetherless) except there will be no return or feedback messages.



Entering Programming Mode

Select the locomotive address you wish to program and set it to either throttle knob. Be sure the address to be programmed is the "display active" throttle when you perform the next step.

Press the KeyRunC and KeyFuncC buttons together, until the Programming indicator PROG LED glows GREEN. Then press the KeyFuncC button to scroll from Paged, Physical or Direct programming modes to Operations mode. The LCD display will show OPS.

Use the left throttle know "L" to select the CV to be modified. Use the right throttle knob "R" to select the value to be programmed to the CV. Press either the KeyModeC or KeySelC buttons to program the selected value to the selected CV.

If you get a bUSY message in response to a KeyModeC or KeySelC button press, the system is temporarily busy. Try again until you get a Good response.

Exiting Programming Mode

To return to LOCO mode when finished programming, press the KeyRunC and KeyFuncC buttons simultaneously. The PROG LED will go out.

Changing Decoder Address

Operations Mode programming cannot be used to make changes to CV01 or the 2-digit short address of any locomotive at any time. An attempt to program a 2-digit address will result in a FAIL message when writing the address is attempted.

Operations Mode programming cannot be used to make changes to a 4-digit long address of any locomotive that was addressed by its 4-digit long address when programming mode was entered. An attempt to program such a 4-digit address will result in a FAIL message when writing the address is attempted.

Operation Mode can be used to write a new 4-digit long address, as long as the locomotive was being accessed using its 2-digit short address when programming mode was entered. To do this select CV18 and press the KeyModeC button then use the throttle knobs to dial up the desired 4-digit address to be programmed. When the new 4-digit address is in the display, press the KeySelC button to write the 4-digit address to the locomotive.



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Maintenance and Troubleshooting

This section provides information on maintaining and troubleshooting problems that may be encountered with the DT100R throttle. It is based on experience and a great deal of correspondence on the Digitrax Email list on yahoogroups.com.

A good battery is key to successful operation in the radio (tetherless) mode. A battery is not needed when the DT100R is plugged into LocoNet. Whatever may appear to be wrong with a DT100R throttle, the first thing to suspect is the battery. Replace the 9V battery with a new or known good battery. Try two or three batteries before deciding there is a fault with the DT100R. Examples of problems caused by weak or dying batteries include:

  • The DT100R operates correctly when plugged into LocoNet, but you cannot control the train after it is unplugged.

  • The throttle loses control of a train after a period of time. See also "Other problems" below.

  • The throttle makes beeping noises.

Don't assume that a newly purchased battery will always be a good battery. A new battery can have a high internal resistance that prevents it from putting out sufficient voltage and/or current to operate the DT100R. Always purchase batteries from a store that sells lots of batteries and therefore always has fresh batteries on hand. Batteries have a "shelf life" as they will deteriorate even if not used.

Do not use rechargeable batteries with the DT100R. Use only alkaline batteries.

No Radio Operation
If the throttle operates correctly when connected to LocoNet but not when untethered, even after ensuring the battery is good, the problem may be that radio transmission has been turned off (secondary option set to 2n). Reset the throttle to normal radio mode either by removing the battery, waiting about 30 seconds, then replacing the battery, or by pressing the KeyRunC, KeyModeC and KeyUpC buttons simultaneously. Either action will reset the throttle to its default values of 01:03. Be sure to release all addresses from the throttle knobs before doing this.

Check that when you first plug in the DT100R to LocoNet, the display says rA:0n where n is a number. This indicates the UR91 is operating correctly.

Another reason is that there are no other throttles still plugged into LocoNet. When a throttle is plugged into LocoNet, the red and green LocoNet wires (wires 3 and 4, the center two) get shorted together, but if there are no throttles or other similar devices plugged into LocoNet they are no longer shorted. The UR91 receiver and the DCS100/DCS200/DB150 Command Stations only use pin 3 (the red wire) for communications. You can either leave a throttle plugged into LocoNet or create a stub cable with pins 3 and 4 connected together.

Throttle Knobs
The throttle knobs are held in place by two 0.050" screws, which can work loose over time. The screws require a 0.050" Allen wrench to tighten them. When tightening the screws, be careful not to put too much sideways pressure on the knob, as the encoder shaft can be damaged.

A defective encoder will show itself as an erratically acting throttle knob where the locomotive speed appears to jump all over the place. The encoder cannot be repaired and must be replaced. You can either return the throttle to Digitrax for service, or you can install a new encoder yourself.

Before returning the throttle to Digitrax or replacing the encoder yourself, take a look under the knobs on your encoders. Earlier versions of the DT100R throttles have a nut around the encoder shaft. If these nuts get tight on the bushing, they tend to pull the encoder or at least strain it away from the internal printed circuit board, causing a problem with contact on the circuit board. If your throttle has these nuts on the encoder shafts, remove the knobs and then the nuts. Re-attach the knobs and test the throttle.

The encoder is available from Digikey (www.digikey.com). The Digikey part is a Bourns encoder, part number 3315Y-1-006-ND (with plastic bushing) or 3315Y-2-006-ND (with nickel-plated brass bushing). The latter is the preferred part. Digikey's description for the encoder is: ENCODER 9MM SQ VERTICAL. Detailed instructions for replacing an encoder are provided below.

Encoder Replacement Procedure

  1. Using a 0.050" Allen wrench remove both knobs from the encoders. Look at the shaft, and if there is a nut around the shaft remove it.

  2. Open the battery compartment and remove the battery.

  3. Remove the Phillips-head screws from the back of the throttle case.

  4. Carefully slide the back portion of the case up towards the cable. Be very careful not to break loose the wires from the battery contacts. There are also 2 wires going to the piezzo buzzer that is mounted to the inside back of the case, and which are easily broken if you are not very careful.

  5. After sliding the rear portion of the case up as far as it will go, gently lift/pull it away from the front half. Keep the front part of the case level when doing this.

  6. Lay the 2 halves of the case down on a table close to one another and make a drawing of where the various wires are connected — just in case they get broken during the rest of the procedure. Note: If this throttle has been serviced before there will be a strip of double-stick foam tape holding the main circuit board down — remove it gently. If this is the first time this throttle has been serviced there will be 4 black plastic tabs melted in place that hold the main circuit board down — remove them with a sharp knife.
    You will also note a separate, smaller circuit board — this is the radio transmitter. This circuit board is connected to the main circuit board by a ribbon cable. The wires in this cable are soldered to the main board. They are not very flexible and break easily, which can be difficult to see.

  7. Now lift out the circuit board — be careful not to lose any of the button tabs.

  8. Flip the circuit board on its back — the encoders are now easily seen. There are 3 metal pins that protrude from the encoder bottom through the board and are soldered in place. One-by-one, heat the solder holding each pin down (using a small 10–20 watt pencil tip soldering iron) while lifting up on that side of the encoder — the pin should pull out. Do this for all 3 pins and remove and discard the encoder. Touch the tip of the soldering iron to the holes on the circuit board and wick off (use a 1/32" wick) any solder remaining in them — you may need to drill out the solder with a pin vise drill but make sure not to damage the solder pads. Insert the new encoder and solder in place. Be careful not to use too much solder and that you do not allow solder to bridge any traces on the circuit board.

  9. Carefully reassemble the throttle but do not attach the back half of the case. Cut a strip of double-stick foam tape (from Radio Shack, Home Depot, Lowe's, etc.) about ½" wide and as long as the case is wide. Fold it in half lengthwise to form an "L" and remove the tape from the outer side. Insert this at the bottom of the board with one side against the battery area divider and the other on the board — this holds it in place so press down firmly. (This is how Digitrax re-attaches the circuit board when they service the throttles.) Placing a small square of this foam tape on the piezzo buzzer also helps to hold the circuit board in place.

  10. Check that all wires are correctly in place and attached, and check carefully that the radio transmitter board and its ribbon cable are in place. Re-attach the back of the case and do a test of the new encoder.
    Before connecting to LocoNet, install a battery and make sure you hear it beep and go to idle. if it doesn't beep and go to idle, open the throttle case and check your work carefully.

Dropping the DT100R Throttle
This is something you should take extreme care not to do, especially if the floor is hardwood, tile or concrete. Depending on the angle at which the throttle hits the floor, the result can be any or all of a damaged or broken encoder shaft, a broken battery spring connector, cracked case, an internal integrated circuit dislodged from its socket or all of the above.

If you drop your throttle, first examine it carefully for obvious damage, such as a broken or bent encoder shaft. Then plug it into LocoNet and test to see if everything works as it should. If it does work properly, unplug from LocoNet and test again in radio mode. If everything still works properly you can start breathing again and remind yourself to be more careful in the future.

If it does not work, the following are the guidelines to repair any damage, or get it repaired:

  • A cracked or broken case can be taped together if possible. For replacement, send the throttle to Digitrax.

  • A broken battery clip must be replaced to ensure good contact with the battery terminal. Either obtain a set of clips from Digitrax and repair it yourself (does not require opening the case) or send the throttle to Digitrax for repair.

  • A damaged/broken encoder must be replaced. See the section on Encoders above.

  • If the throttle LCD display shows hieroglyphics and/or displays SE:1, and/or the throttle emits a clicking or buzzing sound, check that the integrated circuit ("chip") inside the case is properly seated in its socket. This chip can work loose if the throttle is dropped. The piezzo buzzer inside the throttle normally makes clicks when turning the throttle knobs, and when the chip comes loose from its socket the buzzer often makes a continuous buzz. Instructions for opening the case are provided under "Encoder replacement" above.

RJ12 Plug
There are 3 potential problems relating to the RJ12 plug on the end of the stubby LocoNet cable:

  • The locking tab breaks off,
  • The contacts on the plug are bent or otherwise damaged (rare), or
  • The wires are not making a good connection with the contacts in the plug.

The solution to any of these problems is to replace the RJ12 plug. To do this you will need a supply of RJ12 plugs (Radio Shack Cat. No. 279-421), wire-cutters and a 6-wire crimping tool (Radio Shack Cat. No. 279-388, and others). Proceed as follows:

RJ12 Plug Replacement Procedure

  1. When holding the throttle with the LocoNet cable away from you, observe that the blue cable wire is connected to the left end contact on the RJ12 plug (the locking tab, or its remains, will be facing up, and the contacts down) and the white cable wire is connected to the right end contact.

  2. Using the wire cutters, cut the LocoNet cable as close to the RJ12 plug as possible. Make sure the cable is cut straight across, and not at an angle (which would cause problems in the next steps).

  3. Using the insulation stripping feature on the crimping tool, remove the outer insulation from the LocoNet cable to the depth allowed by the crimping tool. Follow the instructions that came with your crimping tool.

  4. Insert the new RJ12 plug in place in the crimping tool. Follow the instructions that came with the crimping tool to ensure you do this right.

  5. Insert the LocoNet cable into the RJ12 plug making sure that the alignment of the blue and white wires is correct relative to the locking tab (note that many crimping tools have the locking tab down when the plug is inserted), and push the cable all the way in.

  6. While holding the LocoNet cable in place in the RJ12 plug, crimp the plug using the crimping tool. Hold the tool in the crimped position for about 10 seconds to ensure a good crimp.

  7. Carefully remove the RJ12 plug and cable from the crimping tool and test the throttle with LocoNet and the Command Station. If operations are not normal cut off the plug and do the install again.

Other Problems and Sources
A number of other problems may appear to be associated with the DT100R throttle, but can actually be caused by other components in the DCC system. These problems include the DT100R working when connected to LocoNet but not in radio mode, runaway locomotives, lost decoder programming, poor radio response, throttle crosstalk and others.

The first thing to do is ensure the DT100R is not the problem, especially if no other DT100R's are experiencing any problems. Remove the DT100R from LocoNet and then remove the battery. Wait about 30 seconds. Install a known good battery, but do not touch any buttons. The throttle should initialize to factory defaults of primary option 01 and secondary option 03, which sets the throttle to 128 speed steps and normal radio mode. Test the throttle both connected to LocoNet and tetherless.

If the throttle still does not operate correctly, and especially if other DT100R throttles are experiencing problems, then check the following:

  • Check the UR91 radio receiver(s) to ensure its PS12 (or equivalent) power supply is connected. If the UR91 power supply is OK then press the reset button on the UR91. If this doesn't work and other DT100R throttles are experiencing problems it is possible that LocoNet has gone into an unstable state. Disconnect LocoNet from the Command Station and connect a LocoNet cable directly from the UR91 to the Command Station (either Jack A or B). Using a second DT100, DT100R or DT100IR throttle, plug it into LocoNet at the UR91 jack. Now test the suspected DT100R. If it works properly then the problem is in LocoNet, and it must be found and fixed. If the DT100R still does not work, the problem may be the UR91 or the Command Station, but since earlier the throttle worked when plugged into LocoNet, the UR91 receiver is the prime suspect. If possible substitute another UR91 and test again. Return a faulty UR91 to Digitrax for repair.

  • Use the green LED in the UR91 as a test indicator. When normally powered the green LED will be lit. As commands are sent from the DT100R, this LED will blink in response to these commands. Outside RF interference will cause the green LED to blink with no throttle commands. If the UR91 is not responding as throttle commands are being sent, the green LED will not blink. Note: this does not apply to a throttle tethered to the UR91's RJ12 jack.

  • If there are UT1 and/or UT2 throttles in use on the layout, check to be sure that any Universal Panels (UP3) are powered with a PS12 (or equivalent) power supply, as the UT1 and UT2 throttles load down the LocoNet voltage.

  • If none of the above work, then there is probably a defective LocoNet cable. A defective cable is found by disconnecting LocoNet at the Command Station, testing with a throttle, then working your way outwards from the Command Station until the faulty cable is found. The Digitrax LT1 LocoNet tester can be used in place of a throttle.

  • The last item to try is a full reset of the Command Station to its factory default values. This is done be resetting OPSW #39. Refer to the Command Station manual for the procedure.

Throttle Response Delays
There will occasionally be a lag in response between when the knob on a DT100R is turned and the locomotive responds. A properly operating DT100R throttle and UR91 radio receiver should have no real delay, and should operate virtually the same as a tethered throttle. A delay of more than 1 second is definitely a problem.

There are a number of potential areas where the environment or specific actions can cause problems:

  • Do not use analog address 00 when operating with radio throttles. The use of address 00 eats up system bandwidth at a rapid rate and causes response delays in other devices. This should be the first item checked when you are experiencing a delay problem. Even if you are not currently operating analog locomotives, be sure that address 00 is set at speed 00. Consider disabling analog addressing by closing OPSW #20 in the Command Station.

  • At Train Shows a potential source of delay is multiple layouts using radio throttles and receivers in close proximity. Two layouts can use up to 10 throttles per receiver, but while the receivers on each layout will detect all commands from all throttles, they will only act upon those from throttles associated with the individual LocoNet connected to the layout. Too many radio signals from too many throttles can cause delays.

  • Digitrax wireless throttles queue commands to minimize current drain and RF traffic. Commands are not sent while being given, only after they are complete or the queue has filled up. Thus constant throttle movement and/or function commands can cause this type of delay.

    The DT100R transmitter sends about 10-12 sets of instructions to the receiver for every change in throttle speed or function. These are sent in a randomly generated sequence and are sent several times with a random amount of time between them so that signals from more than one throttle will not get there at the same time (collision avoidance). This is why so many throttles can be used with one receiver. The multiple sets of instructions guarantee that at least one good set gets through; sometimes it may be the first set and other times the last set, potentially with a delay. The UR91 responds to the first throttle from which it detects a signal.

  • Large metal areas (metallic walls and backgrounds, HVAC ducts, metal pipes, etc.) in the room or hall can cause reflections or ghosting of the RF signal. The UR91 receives all and must sort out the actual RF from the ghosted RF, causing some delay. (It is this ability to sort out real from ghost RF, plus communicate across LocoNet with other UR91s that allows multiple UR91 receivers on the LocoNet.)

  • A poorly tuned UR91 and/or DT100R throttle can cause problems. If you are experiencing delays and the small round sticker on the UR91 is A, B or C, return the receiver to Digitrax for tuning. At the same time return any DT100R throttles that are having a problem with that receiver.

  • Most layouts can get by very well with a single UR91 receiver. Be sure the antenna wires are straight and oriented at about 20° from the vertical in a "V". Also be sure to hold the DT100R in a slightly up position from horizontal and about 8"-10" away from the body. Under poor reception conditions, commands may need to be received by more than one UR91 receiver to get a clear or understandable RF signal.

  • Mount the UR91 receiver as high as practical and at least 1-2 feet away from other layout wiring.

  • Be sure the room temperature is at least 60°.

  • Digitrax suggests a limit of 10 DT100R throttles per receiver, but more can be accommodated depending on the specifics of operation of the layout. Too many throttles will result in noticeable delays.

It is highly suggested that ballistic tracking be turned off on DT100R throttles used in the tetherless mode.



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The following references have been extensively used in the preparation of this material:

  • Chief Starter Set, DCS100 Command Station & DT100IR Handheld Throttle Users Manual. Published by Digitrax, Inc. 02/99.

  • DT100R Radio Equipped Throttle Users Manual & UR91 Radio Receiver Users Manual. Published by Digitrax, Inc. 4/98.

  • Model Railroading with DCC — Don Crano. Click here.

  • John Hills' Model Railroading Web-site.

  • Correspondence on the Digitrax Users and N-Scale DCC (ndcc) Email lists on yahoogroups.com

  • Digitrax Users Problem Log (DUPL) on the Digitrax Users Email list on yahoogroups.com



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The NRMRC is a Not-For-Profit Corporation incorporated in North Carolina.

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Last updated: Saturday July 4, 2009


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Copyright © 1997–2018 North Raleigh Model Railroad Club. All rights reserved. The NRMRC is a Not-For-Profit Corporation incorporated in North Carolina. The various logos and heralds shown here are the property of their respective organizations.