Digitrax Transponding! Don’t Settle for Less

• Proven technology for bi-directional layout control without the need for modifications to your existing DCC system investment.

• Know the detection section and/or zone location and identification of any specific locomotive or other rolling stock equipped with a transponding device. Yes, now your dispatcher will be able to know "who you are and where you are"!

• Location and identification information are updated constantly on LocoNet and can be displayed on a track diagram.

• Adds operations mode readback of CVs to your layout.

• Data received by the system from mobile decoders can be used for display, automation, sound processing and much more.

• Transponding allows you to automate staging yards and other operations.

• You can use Transponding devices in rolling stock in conjunction with transponding detectors on industry tracks to display the location of your freight cars.

• Transponding will bring you an under layout sound system that will follow the locomotives around the layout based on transponding information received by the system. You’ll even be able to put transponders in other rolling stock and generate sounds like couplers, flat wheels, etc. Wow!

• The possibilities are endless! One person even said "It's like LoJack® for your locomotives."

Digitrax Transponding Products are covered by U.S. Patent 6,220,552 and other patents pending.

Used by Digitrax under license from Anthony J. Ireland

Why is Transponding Patented? To make the sharing of this technology with other companies fair and equitable. By securing this technology, and administering it to other professional companies, Digitrax can make sure the technology is conveyed accurately to other companies that want to use it.

What will it take to install Digitrax Transponding on my layout?

1. Install BDL16 series occupancy detector(s).  BDL16, BDL162 and BDL168 can be used together on the same layout.

2. Add RX4 transponder receivers to the zones you want to set up for transponding. (You won't need to cover every detection section on the railroad for effective coverage and reporting. Some areas will be detection only sections while others will have full transponding as needed.)  Use either two RX4s with your BDL168 to set up 8 transponding zones or use one RX4 if you only need 4 transponding zones.

3. All current production Digitrax decoders are transponder equipped. If you have decoders on your layout that are not transponder equipped you can run them as they are or you can add transponding devices (TL1 or TF4) to the locos, cars, or cabooses you want to receive feedback from as they move around on the layout. These devices can be installed with any existing DCC decoder installation.

What components will I need and how much will it cost?

BDL168 $149.99 msrp

LocoNet Universal Occupancy Detector for 16 Detection Sections.

Complete LocoNet Occupancy detection (with NO DS54 required). Gives you local occupancy & zone power status reporting via fascia mounted LEDs &/or computer.

Click here to view BDL168 Manual

RX4 $49.95 msrp

4 ZoneTransponding Receiver Add-on for BDL168.

Use one or two RX4s with a BDL168 to add transponding to any 4 or 8 detection sections on your layout.

Click here to view the RX4 Manual and RX4 Manual Addendum for use of two RX4s

Function Decoders with Digitrax Transponding

Use these tiny function decoders to add more functions (and more fun) to your DCC operation! Install them in DCC equipped locos to add more functions for more DCC controllable lighting. Great for SP and other prototypes that need lots of lights! TL1s & TF4s are a cost effective way to add DCC controlled functions and lighting to cabooses, passenger cars, and other rolling stock. Adding more functions will add to the realism of your layout!

Digitrax function decoders include transponding features that let you use transponder detectors on your layout to feedback position information for each transponder equipped unit. Transponding can be used to automate staging yards, control under layout sound systems and handle other tasks on the railroad.

TL1  $16.95 msrp

Single DCC Function Decoder with Integrated Transponder

Your TL1 can be used as:

1. Function only DCC decoder with transponding

2. Digitrax Transponder

3. Function only DCC decoder without transponding.

• Single 125mA (250mA peak) function output for lights or other functions
• Function can be turned on/off using F0, F1, F2, F3, or F4
• Supports both 2 digit and 4 digit addressing
• Programmable from DCC compatible equipment
• Configurable Strobe feature lets you simulate flashing lights like FRED, Strobes, Mars Lights, etc.
• Compatible with Digitrax Transponding
• Approximate size: 0.461” x 0.31” x 0.161” (11.7mm x 7.8mm x 4.1mm)

Click here for TL1 Instructions

TF4 $20.95 msrp

Quad DCC Function Decoder with Integrated Transponder

• Four 125mA (250mA peak) function output for lights or other functions
• Functions can be turned on/off using F0-F12
• Supports both 2 digit and 4 digit addressing
• Programmable from DCC compatible equipment
• Configurable Strobe feature lets you simulate flashing lights like FRED, Strobes, Mars Lights, etc. on the yellow and white leads
• Standard On/Off Function operation available on green & violet leads.
• Compatible with Digitrax DCC Transponding Systems
• Approximate size: 0.461” x 0.31” x 0.161” (11.7mm x 7.8mm x 4.1mm)

Click here for TF4 Instructions

Digitrax Transponding FAQ

What is Digitrax Transponding? Digitrax Transponding is a proven technology that delivers real two-way communication between your mobile decoders and your control system.

What Does Transponding do?

• Transponding gives you operations mode readback of decoder CVs while they are on the layout (for decoders with this feature).

• Your dispatcher will know where trains and other equipment are located. Feedback from your transponding decoders lets you know the zone location and address of any piece of transponding rolling stock on the layout. This information can be presented on a display panel, your computer or even on your throttle.

• Feedback from the locomotive decoder also can provide information about the speed and other status data for the specific locomotive.

• With transponding, you can FIND the location of a specific piece of transponder equipped rolling stock on the layout.

• Transponding interfaces with an under layout surround sound system so that the sound “follows” your train as it moves around the layout. This is the most realistic sound you can get in a model railroad because you can use speakers that are large enough to give truer sound.

• Transponding can help you automate staging yards and other hidden track. Makes operations much easier.

• Transponding lets you run trains automatically for display purposes or for more interesting single-handed layout operation.

How will Transponding affect the operation of my existing DCC system? Transponding does not affect the operation of DCC equipment. It can enhance the operation of your DCC system by adding more capabilities to your system. It can also be added to other types of control systems for model railroads.

Will I have to add a "feedback bus"?

If you are already using Digitrax LocoNet, you will not have to add any "feedback bus" since this is already incorporated into LocoNet's design! If you are using transponding with a non-LocoNet system, you will need to add LocoNet. Other systems require you to add a feedback bus to achieve these features anyway so, you can simply add LocoNet instead of that feed back bus.

Can the Transponding feature be turned off in decoders that have integrated transponders?

Yes. Digitrax decoders with integrated transponding are shipped with transponding enabled but this does not affect the operation of existing layouts not outfitted for transponding.

Can I use my existing decoders?

Yes! Read on for more information.

How can I use Transponding with existing Digitrax decoder installations?

Once you have instrumented your layout for transponding, you simply add transponder equipped locomotives and you are ready to go. All current production Digitrax decoders are transponder equipped. Older Digitrax decoders models without transponders and decoders made by other manufacturers can add this capability by installing a TL1 or TF4 to existing DCC locomotive installations.

How can I use non-Digitrax decoders on a Transponding layout?

As we said earlier, you can simply add TL1 or TF4s to locos with decoders made by other DCC manufacturers. In the case of some supersonic decoders made by other DCC companies that are not transponding compatible, you can simply switch off the supersonic feature when you want to use transponding. Digitrax supersonic decoders are compatible with transponding and can be used in supersonic mode while transponding.

Can I still operate a non-decoder equipped locomotive on my Transponding layout?

Yes!

Will I be able to use Transponding with other DCC systems?

Yes. You will have to run LocoNet, instrument your layout and install TL1 or TF4 or transponding decoders in your rolling stock. You can then use a computer on LocoNet to display position and id information for transponder equipped rolling stock. LocoNet will run independently of your existing non-LocoNet system.

Will Digitrax Transponding affect my current boosters (power stations), track wiring or locomotive pickups?

No. Digitrax transponding has been designed to retrofit to all existing DCC boosters, track wiring & locomotive pickups without causing any damage or operational problems with existing DCC track signals. Unlike other systems, no high current spikes are used that can cause problems with boosters and wiring.

What about problems with radio interference?

Digitrax transponding does not use high current spikes so it does not lead to potential RFI issues with large installations.

Is Digitrax transponding compatible with signaling systems?

Yes. Transponding is not required to operate signaling systems however, the provision of transponding allows the possibility of the signaling system being able to automatically take control of trains that violate a signal aspect. Transponding can be used to eliminate the "pushy pusher" problem that is characteristic of hardware implemented signal influenced speed control schemes.

What about other methods of train location and identification?

Other methods like bar code reading and RFID systems can be integrated with transponding as part of a total solution.

How can Digitrax systems handle both DCC and transponding without interfering with other track level communication and without adding another communication or feedback bus?

For years we have explained that LocoNet is a true network with expandability to the future. Part of that future is here now with transponding. LocoNet was engineered from the very beginning with things like this in mind.

In the past, Digitrax has focused on DCC compatible products. Now, Digitrax is moving toward becoming a complete layout control company that encompasses DCC and other track power formats as well. Transponding is just the first of many Digitrax products that will work with DCC compatible products and also will work with other power formats, too. As we have always said, "With LocoNet , Digitrax customers really have the best of model railroading. The Digitrax system is compatible with the NMRA "DCC Standards & RPs" but is not limited to them. This is because the NMRA format is just one small subset of Digitrax LocoNet's broader system capabilities."

Is Transponding the same as RailCom?

NO! RailCom is the proprietary technology of another DCC manufacturer. It requires modifications to existing DCC equipment for proper operation.

How Does Digitrax Transponding relate to the NMRA's "DCC Standards & RPs"?

The current NMRA proposal for bi-directional communication is, as yet, unproven technology. Significant technical problems exist for use on large layouts that have yet to be addressed.

It is Digitrax’s position that the NMRA “Standards & RPs” do not now, nor should they ever, prohibit the use of the rails for non-DCC uses like regular DC control, signaling, block detection, transponding or other types of non-NMRA command control. In addition, the “Standards and RPs” must maintain backward compatibility with existing equipment.

Why didn’t Digitrax “give” Transponding to the NMRA?

Here is a brief history of the development of "bi-directional" communication as applied to model railroads:

Our customers asked for bi-directional features. We talked to the NMRA DCC working group and other DCC manufacturers and it was decided that there was “no way” it could be done without modifications to all existing decoders and command stations. AJ Ireland began exploring the possibilities for bi-directional communication outside the committee because he could not live with the idea that we would have to ask our customers to make modifications to all existing DCC equipment to add this feature. The NMRA continued to explore a bi-directional communications scheme that would require significant modifications to existing DCC equipment for it to operate with new command stations that would have this capability.

About a year later, AJ discovered a way to make bi-directional communications work with no modifications to existing equipment. All that would be needed is transponders in the locos and instrumentation on the track. Transponding would not preclude operation of existing DCC equipment and would work on any DCC system. He patented his ideas and licensed the patent to Digitrax. Digitrax began shipping transponder equipped decoders. Since then, transponding has been widely accepted and installed on layouts all over the world. Our customers have what they asked for and we are now working on revealing the additional capabilities included in transponding technology.

AJ Ireland and Digitrax have offered licensing for transponding to all other manufacturers at a nominal rate with very reasonable terms. Transponding and bi-directional communication are very technical subjects that are not easily explained to non-engineers. He is very happy to share this information with other engineers and to license the technology to other professional companies. Had AJ offered his method of bi-directional communication to the NMRA, it is likely that we would still be trying to explain it today. Another big factor in the decision not to offer the technology to the NMRA was that the NMRA DCC working group does not have well defined rules that are followed by the group for moving proposals forward and it was felt that the political climate within the group would likely have prevented the proposal from being accepted.

Another problem for presenting transponding to the DCC working group is that the NMRA “Standards” do not cover the command bus/network . DCC manufacturers use a several different methods of system communication that are not technically compatible. Because Digitrax uses LocoNet for its network communications, we were able to develop a truly bi-directional communication method based on LocoNet that does not require modification of existing DCC systems. Since LocoNet is an integral part of the Digitrax Transponding system, and LocoNet (or any other bus/network), is not an NMRA “Standard” there is another ”can of worms” that would have to be worked out.

In the mean time, it seemed to be a better choice for our customers to go ahead and make Transponding available as soon as possible.

Now, several years down the road, another DCC company has presented its proprietary bi-directional communication proposal that will require modifications to all existing DCC equipment to be considered as an NMRA RP. It appears that this proposal will be (or may already have been) accepted. Once the technical details become available to other manufacturers Digitrax will assess this new technology and determine whether it should be incorporated into our system. The good news for Digitrax and our users is that Transponding does everything this other technology can do and is a proven technology. The other good news is that Digitrax LocoNet is very flexible and will be able to handle the new format if we discover that we need to add it in the future.
A Little History of Bi-directional Communication

Digitrax has been interested bi-directional technology for a number of years. The first viable technology that was evaluated by the NMRA was the Zimo Train Number Identification technology suggested in 1996. An extension of this to Operations Mode Read capability would provide a usable mechanism to both track trains and read back any operational status information desired, such as speed, load etc.

Digitrax had concerns about the “shorting the track power” used by Zimo. Ultimately the Zimo proposal was incorporated into the NMRA’s DCC documentation as a “Technical Note.”

After the Technical Note was finished, several DCC companies worked on other bi-directional schemes. By 1997, it was generally agreed among the DCC community that there was no good solution to the bi-directional issue and most development on the topic had come to a stop.

In response to customer requests, AJ Ireland began to explore the bi-directional issue again late in 1997. Upon review of the work that had been completed, he came to realize that for Digitrax to develop and support any bi-directional technology for its customer base the following criteria had to be met:

1) The technology had to work with existing boosters and command stations with no modifications required.

2) The technology had to be compatible with existing decoders and rolling stock on a layout.

3) There had to be a minimum impact to the hardware designs of decoders, especially the smaller Z-scale size units, and the software overhead had to be minimized.

4) Any additional components that had to be added to decoders to achieve bi-directional communication could not impact the reliability of the designs.

After many resources were invested in development, AJ was able to come up with a transponding method that fit all of the design criteria established. This method also allows the decoder to return any type of bi-directional data that is desired and is able to return information without being addressed by the system. The idea was unique from anything that had been proposed previously. AJ obtained a patent on the technology. AJ and Digitrax have offered to share transponding technology under a nominal fee license agreement with other DCC companies. The intent was never to keep the technology from other companies but rather to facilitate its use in all DCC companies. In this way Digitrax was able to bring an exciting new technology to our customers within a reasonable time frame and be able to share this field proven technology with other companies.

As a member of the DCC Working Group, we have observed the evolution of several versions of a proposed NMRA bi-directional format since 2000. We have expressed a number concerns with each of these versions as outlined below. Our concerns have not been taken into account by the other members of the group. In addition, we are concerned that the DCC Working Group has not followed proper procedures in moving this proposal forward.

Some concerns we have with the current NMRA bi-directional proposal are:

1) The Command stations must be changed to provide a modified track waveform. This represents a cost for existing systems, if in fact they are modifiable. The boosters may also need modification, if the detectors are not capable of carrying and switching the full track current rating.

2) There have been reported problems with a number of widely used decoders because of the proposed DCC waveform modifications. Of concern is the reported need to modify the decoders by adding parts to deal with the problems associated with turning off the track at each preamble.

3) New decoder designs need to have many new discrete components added. Additional decoder software is also required, as for all designs for bi-directional techniques. It appears that several dedicated I/O pins are need for the current “reference design” to create a 20mA current loop. The additional components become a problem in Z-scale sized decoders.

4) Lighted passenger cars and other uncontrolled loads need to be modified so as not to load the tracks at the bi-directional data times. This is a required hardware change. It is still not clear how many decoder, lamp or capacitive track loads can be present before the system has problems.

5) The power for the return data has to come from an onboard energy source. This is also a constraint for smaller Z-scale designs favored by the N-scale users. Of concern is the sharing of the internal microprocessor power storage to implement the data feedback. The impacts on ESD ruggedness and a hostile track power environment have not been fully explained.

6) When bridging 2 or 3 detectors the current loop (e.g. 20mA) is now split amongst a number of split paths. It is a concern to increase the data current when the onboard storage is so constrained.

In our view these concerns make the current NMRA bi-directional proposal impractical for our customers to implement.

Digitrax is currently shipping transponding products that implement all the equivalent features of the bi-directional RP without many of the problems. Digitrax transponding has been in use since 1998 and is a field proven technology.

Several customers have asked whether Digitrax will support the NMRA bi-directional method. Ultimately, if there is sufficient demand for the method embodied in the RP it is possible to add it to future Digitrax products. However, Digitrax feels that this technology puts an unnecessary burden on current DCC users by requiring so many hardware changes to existing systems especially when there is a better technology available that does not require these changes and that does not change the character of DCC.