Asymmetrical DCC Technical Information

Lenz GmbH is pleased to introduce Asymmetrical DCC, a cost effective solution to model railroad location specific commands.

Available now in our GOLD Series and Silver Series decoders

From the time we invented DCC we have always desired a simple solution to influence the behavior of a train in specific sections of the layout.  Now with the introduction of Asymmetrical DCC we can finally realize these objectives.

Why would I want to have localized train control in addition to DCC?

When operating a model railroad it is often desired to have some trains under operator control and others running in the background.  This allows your layout to come alive even if you only have one operator.  You can also use asymmetrical DCC to enforce speed control through important sections of your layout or to stop a train in a siding, in the station, or before an occupied rail crossing.

What can the user configure Asymmetrical DCC to do?

Restricted speed enforcement.

Cost was the key design criterion for developing Asymmetrical DCC.  It only takes 5 diodes to create an Asymmetrical DCC signal which the user can easy add to sections, where automatic control is desired. The cost to detect and process asymmetrical DCC signal information inside a decoder is only pennies and will be included in all our new Gold Series Decoders and Silver Series.

How does it work?

A normal DCC signal is symmetrical meaning that the positive voltage and negative voltage is the same. In asymmetrical DCC there is a slight difference between the positive and negative components of the DCC signal.  This is achieved by feeding the DCC signal through a set of diodes, three diodes in one direction and two diodes in the other direction. The information transmitted to the decoder can be further modulated by modulating the time the DCC signal is symmetrical and when it is asymmetrical.

Aren’t there already other solutions for doing this?

Stop generators, reverse DC and the Tech Note on Signal Controlled Influence all attempt to address the goal of influencing the operation of a train in a specific location, but all of these previous solutions suffered from complicated wiring and cost.

Is it compatible with all my existing DCC equipment?

YES!  Asymmetrical DCC is a proven technology that is fully compatible with all NMRA DCC products in the market.

Will this be added to the NMRA DCC Standards and RPs?

At the DCC spring meeting of 2000, Urs Meyer of Umelec presented the first proposal for asymmetrical DCC.  This proposal was only for stopping a train in front of a red signal and was not direction specific.  In 2003 of RP-the NMRA approved the first use of asymmetrical DCC in RP-9.3.2. 

What Features will be supported first?

The first feature will be Automatic Breaking Control.  This will allow location specific stopping of trains where ever desired and also allow integration to signaling systems.

What Products will be available?

To influence the operation of a train you need decoders that support Asymmetrical DCC and Asymmetrical DCC generations.  All of our Gold series decoders will support Asymmetrical DCC as well as a growing number of decoders from other manufacturers.

We are shipping the BM-1, and BM-2 and 3 will follow in the coming year.

·       BM1 – Simple 5 diode asymmetrical generator - now shipping

·       BM2 – Controlled by an external signal both stop and restricted speed control can be achieved.  Push pull and multi unit trains can also be successfully operated.

·       BM3 – Full block occupancy detection and Asymmetrical DCC built into a single unit.  Can control an external signal system.

What’s Next?

Asymmetrical DCC has already proved itself to be a very powerful addition to enhance model railroad control.  It offers a very low cost method for having multiple trains run in the background on your model railroad yet still be under control. We will continue to refine and expand on this key concept to further enhance the joys of model railroad operation.