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Throttle Network:


Summary: LocoNet is the throttle network designed and used by Digitrax to communicate between throttles, command stations, boosters and other accessories. Interfaces are available to allow a computer to be connected to LocoNet. Several other DCC Manufacturers also employ LocoNet as their throttle network.

See more Throttle Networks
General information
Common Name
Used by
Reference material URL Manual Link
Has computer interface Other
Year Released 1996
Year EOL
Network Details
Network Type Peer-To-Peer
Number Of Max Devices
Is open source No


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What is LocoNet®

LocoNet® is a trademark identifying a LAN for model railroads designed and patented by Digitrax Inc. Portions of LocoNet® are covered by US Patent Number 6,275,739.

Prior to the year 2000, the system functioned at less than 20% of available message types and commands that LocoNet is designed for. LocoNet is designed for future expansion, where today's devices will still be able to process messages even it they cannot use it. It is also possible to use a computer with multiple ports to route and bridge messages across several LocoNets, expanding capacity.

LocoNet can interface with a computer via a a device such as the LocoBuffer or Digitrax's own PR3, PR4 or MS100 interfaces. For more information on interfacing a computer to your Digital Command Control system, please see Connecting your computer to DCC

Network Details

LocoNet is a networking technology that uses CSMA/CD (Carrier Sense Multiple Access/Collision Detection), similar to the Ethernet network commonly used to interconnect various network devices, such as computers, high speed modems, printers, etc., but optimized for model railroading.

  • Carrier Sense: Message sync is done within the message stream as all devices on the network see all the messages transmitted. The devices also know when the network is busy.
  • Multiple Access: The ability of all devices to access the network and generate messages on their own, without direction from a central controller.
  • Collision Detection: When two devices try to send messages at the same time, creating a conflict, that they resolve those conflicts on their own.
  • LocoNet is designed to allow operation at 100% capacity with fewer than one collision in 300 messages, less than Ethernet allows.
  • LocoNet is similar to the standard ISO Network Model with pipelined multilevel protocol stacks and queues.

LocoNet Basics - An Introduction

Digitrax UT1 Throttle

Loconet is part of a Digital Command Control system designed by Digitrax to connect throttles, boosters and other devices to the command station. LocoNet is a Peer-to-Peer Local Area Network (LAN) designed for very high traffic capacity and free-form wiring, future system expandability and ease of upgrade. It is a separate circuit from the track power used to run model trains.

Digitrax developed LocoNet to handle the communications between throttles, accessory decoders, and other devices that need communications with the command station. The command station processes, assembles and routes this and other information to either the track or to the LocoNet only. LocoNet allows fast two-way communications between devices not related to running the model trains.

Digitrax labels the LocoNet connections on their command stations as A and B, both are the higher current throttle type. For programming of the command station, a throttle is connected directly to either LocoNet jack.

LocoNet B

A LocoNet jack may be identified as LocoNet B. It indicates a LocoNet Booster Connection, as part of a booster network. LocoNet B limits the current to 200mA. It is meant to connect the command station and boosters together, not power devices like throttles. Since most command stations are integrated with a booster, this connection is not common.

  • The RailSync signals present are for use by the booster.
  • Some command station/booster units offered by LocoNet licencees may have a LocoNet B connection.

Loconet T

LocoNet T indicates a higher current is available to power Throttles, stationary decoders and other LocoNet devices. The T indicates a connection for the Throttle Network. Many devices have jacks which are just labelled LocoNet, which are LocoNet T connections. The LocoNet T connections lack the RailSync signals the LocoNet B connections have, so some devices may not work when connected to a LocoNet T jack.

The front and side jacks on a UP5 panel are LocoNet T, and are not to be used to feed additional downstream devices.

LocoNet ID

The LocoNet ID is used with wireless throttles. The default LocoNet ID number is "00." This is not the same as the deprecated Layout ID concept used by NCE.

Any throttle connecting to a UR90, UR91 or a UR92/UR92CE Utility Radio Panel requires a valid LocoNet ID. When a throttle is plugged into the LocoNet it will discover and attach itself to that ID. The throttle will display rA or Ir indicating it has detected a radio or IR device, as well as the ID number. Remember, the wireless features must be enabled on the throttle for this to work.

LocoNet ID allows multiple clubs in close proximity, such as a train show, to use their radio throttles without interfering in the operations on another layout. Note that this is not the same RF interference causing problems with communications between the UR9x and the throttles. This is only to prevent commands from one layout's throttles from being accepted by another layout's receivers.

The throttle must have a battery installed to operate in this manner.

Changing LocoNet ID

It is possible to change the LocoNet ID if there are conflicts. The LocoNet ID number can be changed, either by following the instructions from Digitrax or by using the LocoNet ID tool in JMRI. After the LocoNet ID has been altered, all wireless throttles must be physically disconnected then reconnected to the LocoNet to update the LocoNet ID they connect to. Otherwise, the wireless throttle will not work. Tethered throttles are not impacted by the LocoNet ID change.

It is possible to change the ID number using an appropriate throttle if a computer is not available.

LocoNet Details

For more detailed information on LocoNet, see the LocoNet Personal Edition documentation from Digitrax.

As mentioned above, LocoNet is a CSMA/CD system.

  1. Carrier Sense - Devices monitor the LocoNet bus to decide when it is safe to transmit a message
  2. Multiple Access - All devices share the same LocoNet segment, so all messages are seen by all devices
  3. Only one device can be transmitting at a time
  4. Collision Detection - Devices monitor the LocoNet during transmitting, to determine if their message was corrupted by another message
  5. Priority based timing allows a high priority device such as track sensors to transmit their messages with with higher priority than throttles
  6. If two devices attempt to transmit at the same time, both messages are discarded and both devices have to retry. Devices with different priorities should not cause collisions with each other.
  7. A CSMA/CD network characteristic is the rate of collisions increases with network loads above 25 - 50% of the theoretical capability. For good performance load to not exceed the 10-20% of the capacity.

LocoNet operates at a speed of 16.66 kiloBaud, with one start bit, 8 data bits and a stop bit, or more than 1600 characters per second. This structure makes interfacing the LocoNet to a computer's serial port very easy. In fact, several computers may be on a LocoNet.

Throttles are low priority devices. Their messages are not as time sensitive as those of an occupancy detector. The system will increase their priority as transmission failures increase until the message is successfully sent. Then the priority is reset to its normal level.

More devices, more traffic. Every device that wants to talk waits a specified amount of time after the last message before attempting to send a message. After the wait time expires, another slice of time is used to determine priority: High priority devices get the first chance, low priority devices must wait longer before attempting a transmit.

The LocoNet system is a different from the NCE Cab Bus, which is a polled system, meaning "speak when spoken to". As more devices are added to a polled system, response times decline as it takes longer to poll a specific device.

LocoNet Power

The LocoNet system has the following voltages and currents:

  1. The command station has a 15mA pull-up, with a nominal 12V on the DATA signals (This is the LocoNet Termination).
  2. Input impedance of a LocoNet device must be more than 47kOhms. This allows a max draw of 100uA at the minimum voltage.
  3. Minimum voltage is 5V
  4. It would require about 150 LocoNet devices to load the network to its maximum. This is much more than most layouts would have.

What are the Wires used for?

The wires in the LocoNet cable are used for the following signals (referenced to the pins on the connectors).

Pin Signal Voltage Colour
1 Rail Sync Positive (B) 7VDC White
2 Ground 0 Black
3 LocoNet 14.5VDC Red
4 Green
5 Ground 0 Yellow
6 Rail Sync Negative (A) 7VDC Blue
Colours can vary depending on the cable manufacturer.
RailSync is a differential signal, measuring from pins 1 to 6 should read 0V. Measure to Ground pin to determine voltage.

LocoNet B has the RailSync signals present for a Booster, limited to 200mA of current. LocoNet T will have 12VDC/500mA present on pins 1 and 6 for powering throttles and other LocoNet devices, measured to the ground pin. For this reason, boosters must be connected to LocoNet B. Utility panels (LocoNet T) use a diode matrix to derive the needed 12VDC from the RailSync lines, which is provided to the front jacks.

Boosters must not be connected to the front jacks of a utility panel.

Opto Isolated Boosters

Some boosters come with a label stating OPTO or OPTO-ISOLATED. What that means is the LocoNet connections on pins 3 and 4 are isolated through an optical isolation device, and the grounds (pins 2 & 5) are not connected. This prevents currents from flowing through LocoNet's ground wires to return to another booster. They are an extra cost device, and for most applications are not necessary.

As the picture shows, the modules are wired for DCC ou DC, so it is possible the modules are wired for common rail operation to accommodate analog (DC) operations. Never attempt to use analog and digital at the same time on a layout!

LocoNet Termination

Main article: LocoNet Termination

Termination is provided by the command station, or a device such as the PR3/PR4. In the absence of a device providing termination, the LocoNet may not work. Termination can also be provided by an external device.

  • There can be only one device providing termination.

Phone Lines?

A new Digitrax DCC set contains several flat black cables with plastic telephone plugs on the end. The booster/command station (either DCS100, DB150, or Zephyr command station/booster) has 2 RJ type telephone jacks on the front or rear. The throttle also has a cable terminating in a telephone plug. The universal panel (UP5) has two telephone jacks in the front. There may be a short piece of cable with a plastic plug on one end and colored wires on the other end (LT-1).

LocoNet Cabling

Digitrax recommends the use of 26AWG 3 pair such as a flat, 6 conductor 130 Ω ribbon cable with RJ12 6P6C plugs crimped on. This reduces Radio Frequency Interference by balancing the connections. Using pairs of wires reduces the impedance of the cable. The cabling may be branched into a Star or Bus configuration. Using the six-wire flat cable, lengths of up to 300m are possible. Depending on the cable's electrical characteristics a total run of LocoNet cable can be up to 600m. [1]

  • Do not loop the LocoNet back onto itself.
  • Runs of up to 600 m are possible,
    • No more than 180m between devices

Cabling Basics

The flat six wire cable is recommended by Digitrax for the following reasons:

  1. The three conductors on the left are an effective mirror of those on the right, creating a balanced cable.
  2. By paralleling two pairs of conductors for the Ground and LocoNet connections, their effective impedance is reduced, allowing for longer runs.
  3. If a Ground or LocoNet conductor is broken, the network will still function.
  4. The two outer conductors carry RailSync, a differential signal, which results in a robust signal for thousands of feet of LocoNet cable.
  5. The balanced nature of the cable and the way the signal currents propagate in this "RF Quad" configuration generates the lowest possible RFI radiation and EMC susceptibility. The signals are less susceptible to interference by other wiring nearby, such as the power bus, or to cause interference.

Digitrax strongly advises against using Category 5 or 6 Ethernet cabling, as capacitive and inductive issues will introduce problems, especially in long runs. CAT 5/6 wire is carefully designed and manufactured for a specific purpose, and its parameters are not suitable for LocoNet wiring.

Shielded twisted pair conductors or Cat4 or higher network cables will degrade the signal integrity, reducing the practical length of a LocoNet network.

Welcome to Digitrax Networking

Digitrax DCS100 Command Station/ Booster

Welcome to the world of Digitrax DCC - where trains are controlled by computer(s).

This is an advanced topic.

The DCS100/ DB150/Zephyr command station is a computer. The throttle is a computer. The decoder you just installed in your loco is really a small computer. Digital Command Control is all about computers. If you are familiar with computers, especially networked computers at your school or office, you are well on your way to understanding DCC.

If you're not familiar with these terms, please see our layman's explanation of DCC.

Computers talk to each other through data communication lines. Typically, these lines are similar to a telephone line - either a flat-ribbon cable like the line to your telephone set, or a thick cable like the one behind the wall into your telephone jack. In computer language, this type of wiring and the signals that travel through the wires form a Local Area Network or LAN. Industry standards which specify the details about these signals, which wires in the cable they travel through, what the colour of the wires should be, the type of connector plugs to use, and other things.

Digitrax's throttle network is a Local Area Network that is not very different from a computer LAN. Except that, instead of calling their Local Area Network a "LAN", Digitrax calls it a "LocoNet." That is all LocoNet is - a Local Area Network, optimized for use on a model railroad. Which is why you've got a whole bunch of stuff that looks like telephone cables, plugs, and jacks. We won't get into the mysteries of what types of signals go down these wires - because we don't have to. We're more interested in installing those cables/jacks so that we can get to running the trains. What we'll do over the next few sections is introduce some of these wiring standards, show how to wire the LocoNet and, in the process, try to take some of the mystery out of LocoNet.

LocoNet Interface Devices

To communicate between a computer and the LocoNet, you need a translator that will understand both of them. There are two options available: the Digitrax interface and the third party LocoBuffer.

The current Digitrax solution is the PR4

  • PR4
  • Multifunction USB to LocoNet connectivity.
  • MS100 - Digitrax's own computer/Loconet interface device.
    • Has been significantly outdated by the LocoBuffer II
    • Connects via RS-232. Some users report RS-232 <-> USB adapters work.
    • It has now been discontinued. Its replacement is the PR3.
  • PR3
    • Discontinued
    • Replacement for MS100
    • Uses USB-2.0 for connection to computer.
  • LocoBuffer - Third party hardware interface device
    • History
      • Developed by John Jabour in response to speed and platform restrictions of the MS100. Technically was not much better than the MS100
      • Was available in complete or kit form from the designer until he decided not to make them available any more.
      • Manufacturing of the unit to was transferred to RRCircuits.
      • Original Locobuffer is no longer available.
  • LocoBuffer II - Developed by RR-CirKits as a replacement to the original LocoBuffer.
    • Faster, smaller, and more up to date.
    • Certified by Digitax
    • Connects via RS-232. Many users report RS-232 <-> USB adapters work well.
    • Faster serial connection, fewer dropped packets.
  • LocoBuffer-USB - Developed by RR-CirKits as a replacement to the LocoBuffer II
    • Replaces LocoBuffer II
    • Connects directly to USB port
    • Powered from USB connection and Rail Sync lines, no external power supply needed.
  • LNGateway - Opensource Arduino based DIY interface device
    • Connects via USB
    • Opto isolated and powered by USB and Rail Sync lines
    • Intended to be used together with JMRI as low-cost solution for connecting WiFi throttles
    • Circuit design files and source code available on the LNGateway Github pages


  • DB-25 serial RS-232 input
This unit is obsolete. Originally released in 1996.

From the Digitrax Website:

The MS100 Computer Interface is designed to let an IBM compatible computer with RS232 communications port monitor Digitrax LocoNet. The MS100 is a signal level translator between LocoNet and a 25 pin DB25 style RS-232 port. It is basically a dongle that plugs into the 25 pin RS-232 serial port, with an additional cable connecting to LocoNet.

Application software running in the computer can then interpret the activity on the LocoNet and report back to the user via the computer screen. The interface was primitive, passing all messages to the computer, which results in additional overhead.

Digitrax PR4

The PR4 supersedes the PR3.

  • Multifunction USB to LocoNet.
  • Optimized for Direct mode
  • LocoNet is Electrically Isolated from USB port.
  • “SoundLoader” decoder compatible.
  • Programs most DCC decoders.
  • Standalone operation: No requirement for a Digitrax Command Station.
  • LED status lights.
  • Opto-isolated.

Works with Mac and MS Operating Systems. PR4 software is MSWindows only, JMRI compatible (MacOS).

(Dec. 2017)

Digitrax PR3

  • USB-2.0 input
  • May be used with Digitrax' "Soundloader" program (currently Windows only).
  • Compatible with Windows 2000, XP, and Vista (Windows 7 status currently unknown)
  • Compatible with JMRI on Mac OS 10.4/10.5 and Xubuntu 10.10
  • Only requires a power supply for use with "Soundloader" program.
  • LocoNet® terminator included.
  • Software configured
  • Not Opto-isolated.


LocoBuffer II

LocoBuffer-II specs:

  • DB-9 serial RS-232 input
  • Opto isolation (if not using LocoNet® powered mode)
  • Buffered input and output allows use with all operating systems. (Linux, Mac, MS Windows)
  • Hardware handshaking using RTS/CTS (also includes DTR/DSR turnback required for MS Windows XP)
  • Packaged unit size 1-1/2" x 3-3/4" x 3/4"
  • Ready To Run
  • Optional Package available with cables, (DB-9 or Mac DIN-8, and 14' LocoNet®) plus 9V power supply
  • LocoNet® terminator included. Rev-f terminator is built in. (Allows you to use your LocoBuffer-II to add LocoNet® device compatibility to other systems)
  • DIP switch settings for all options
  • MS-100 compatible plus 19,200 and 57,600 standard Baud rates
  • Serial Boot Loader programmable for upgrades (Does not require special hardware)
  • Power from 9V-12V AC-DC
  • Optionally LocoNet® powered from rail sync lines
  • Digitrax LocoNet® certified.
  • Suggested Retail Price: $69.95.

LocoBuffer-USB Features:

  • USB 2.0 to LocoNet® interface
  • Optical isolation between USB and LocoNet® prevents potential grounding problems
  • Buffered inputs and outputs allow use with all USB supported operating systems
    • CD with drivers for Linux 2.4, Mac OS-9, OS X, MS Windows 98SE, ME, 2K, XP
  • Packaged unit size just 1-1/2" x 3" x 3/4"
  • Ready to run unit
  • Internal LocoNet® terminator.
    • Allows a LocoBuffer-USB to add LocoNet® device compatibility to other systems
  • 57,600 Baud interface speed
    • No jumpers or switches to set
  • Compatible with existing software
  • Installs as a serial port
  • Hardware handshaking using RTS/CTS
    • Includes DTR/DSR turn back required by MS Windows XP
  • Boot Loader for firmware upgrades
    • Does not require special hardware to install upgrades
  • Powered directly from USB and LocoNet® Rail Sync lines
    • No external power adapter needed
  • Internal option connector allows for future features
    • Planned optional programming track output
  • Includes 3' USB A-B and 14' LocoNet® cables
  • Suggested Retail Price: $ 74.95

LocoNet USB Interface 63120 by Uhlenbrock

The USB-LocoNet Interface build by Uhlenbrock Elektronik GmbH offers a number of advantages. As with the LocoBuffer-USB, it uses a microcontroller for precise LocoNet timing, reducing the load on the computer.

  • Opto-isolated
  • Modes:
    • LocoNet Direct
    • Only valid LocoNet messages are passed to the computer

L.Net Converter - ESU

ESU has added the L Net Converter or ECoS Throttle Integration Adapter.

It will allow connection of LocoNet throttles to an ESU command station such as the ECos. This will allow you to keep your existing LocoNet devices, such as feedback modules, as well as your Uhlenbrock or Digitrax throttles.

This device works with the ECos or the older Central Station (60212) command stations.

Feedback Modules

Loconet modules such as those for track occupancy detection. The L.Net Converter allows those devices to connect to the ECoS, for activating routes or shuttle train control. Use of s88, Loconet and ECoSDetector feedback modules is possible at the same time.


The L.Net Converter solves the communications problem: the ECoS will send loco and turnout commands via the L.Net Converter to the devices connected.

Ethernet to LocoNet

  • Ethernet to LocoNet interface with integrated Power supply.
  • Optical isolation between computer and LocoNet.
  • Running with Rocrail
  • Do It yourself package or Pcboard is available
  • IP adress selectable via EEprom settings
  • Suggested package price €65,-- , pcboard only €9,--
  • Pcboard is double sided with silkscreen and solder mask. Through hole connected.
  • Rocrail.net

LocoNet Construction

Network Topology

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LocoNet connections can be arranged in a number of ways: Star, a Bus or Daisy Chain.

LocoNet should not be arranged into a loop, as it is very important to make sure the RAIL SYNC signals are connected correctly and in sync. Otherwise, they will cancel out. For this reason, Digitrax does not recommend wiring LocoNet in a loop.

Making a LocoNet cable is easy. Wiring a socket is not easy, and can introduce problems. You also do not have to follow the example of the cable with RJ12 plugs, but it is important to get the wiring correct to avoid problems.

LocoNet Splitters

There are a number of ways to split your LocoNet. Passive splitters will work, but they must be straight through in design, not those that flip connections. While this may work with a telephone, it causes problems with LocoNet.

Splitters, such as the Digikeijs DR5097 DigiNetHub, are specifically designed for LocoNet.

For best results, power the Utility panels (UPx) to maintain signal strength. Do not use the front jacks to split the LocoNet, as they often replace the RailSync signals with DC power for the throttles.

Digitrax UP6Z

The UP6Z is a LocoNet splitter, which has six jacks, two on the rear and four on the front. It is also used to reduce track voltage for Z scale model railroads, allowing the track bus to be supplied by a lower voltage than the Digitrax booster can provide, at a maximum of 3A. This feature is optional, so the UP6Z can be used with any scale.

The device doesn't not require power to operate. It has a power plug, but it is just there to fill a hole in the cover, and doesn't connect to anything. It also has no battery saver circuitry.

Standalone LocoNet

It is possible to construct a standalone LocoNet, without a command station functioning as the Master. As the command station also provides termination to the LocoNet, this will need to be provided. Devices such as the PR3 and PR4 can do this, or it can be constructed using a power supply. In this arrangement LocoNet devices can communicate amongst themselves.

LocoNet Troubleshooting

Also see the Digitrax Hints page for a list of Audible Alerts

Construction Issues

Many LocoNet problems are not really a LocoNet issue, but mechanical or electrical issues with the cabling.

Break in LocoNet Signal

One issue is that the LocoNet signal from the command station is only present on one of the two LocoNet (red and green) wires. Usually the command station provides the LocoNet signal on Pin 3 (the red wire). At some point a device, such as a throttle, will bridge pin 3 to pin 4.

Devices such as a throttle, the LNRP or a UP92 will provide this bridge. The DT400 is known for not bridging pins 3 and 4. Another culprit is the UP5.

The LT5 LocoNet Tester can be used to determine if bridging is taking place, and then be used to find out where the bridging is occurring. It can also determine if the LocoNet signal is on the red wire before the bridge.

If a downstream booster stops responding, it is possible there is a break in the wires carrying the LocoNet signal from the command station. If there is a utility panel connected between the command station and the booster, and this problem only appears when a throttle is unplugged, one of those cables has an issue. Removing the throttle from the panel disconnects the bridge between wires three and four on the LocoNet cable.

If there are multiple panels between the command station and the booster, any one of those panels can be used to bridge the two LocoNet wires. Using a throttle, you can isolate the cables involved by testing each panel until the issue appears.

If there is no command station on the LocoNet, a LocoNet termination can also connect lines 3 and 4.

Crimping Issues

Improperly crimped connections are common. It is important to use the correct type of connector and a quality crimping tool.

There are two types of RJ connectors available on the market depending on the wire type:

  • Solid Wire
  • Stranded Wire

Using a solid wire RJ connector on a stranded wire may work, but it is not reliable. If it were, there would only be one RJ connector for both types of wire. Using a connector meant for stranded wire to terminate a cable with solid conductors will introduce issues as there are two prongs which penetrate the insulation, resulting in the potential for the wire to break at that point. Nicks in solid wire weaken the wire at that point.

Incorrectly crimped terminations may result in a cable which "tests good" with an LT1, but will not work with LocoNet devices.

Troubleshooting a LocoNet Cable


Using a DMM, measure the voltages on the cable, referencing the Ground terminal on the command station.

  • A healthy working LocoNet should have 10V or more available between ground and pins 3 or 4 of the RJ connector.
  • A cable with a poor, high resistance connection will see a reduced voltage on the pin(s).
  • The voltage should be 9 to 10V on those pins.

LocoNet Wiring Standards.jpg


The RailSync wires (the outer pins on the RJ connector) can become an open circuit, without having an adverse effect on many of the devices they connect. RailSync is a low voltage/low power representation of the track signal. Your DMM can pinpoint the issue. These signals are not in phase, so do not short them together.

Digitrax Zephyr Specific

With a DCS100 integrated command station/booster or DB150 booster, only one of the LocoNet wires (3 and 4) is driven. Connecting a throttle bridges them.

In most LocoNet implementations, the two LocoNet wires are paired together. Throttles, DS54s, and the LocoBuffer all pair pins 3 and 4.

In some situations, this may not happen. Should a LocoNet device not work, this can be the issue. A common culprit is the DCS series Zephyr when connected to LocoNet devices. A Zephyr internally connects the two wires via a resistor. The devices do not work as the signal is missing.

The solution can be a shorting plug, made from an RJ connector. A wire is fitted to connect between pins 3 and 4, which is then crimped in place. The shorting plug can then be inserted in any available spare LocoNet jack, which should resolve the problem.

LocoNet Termination Issues

LocoNet Termination for this discussion refers to the supply of power to the Rail Sync lines. If you are looking for terminations on a power bus, please refer to the Bus Termination page.

Some devices may not work if the LocoNet is not terminated correctly. Many LocoNet devices rely on the RailSync wires for power. A low current 12VDC source can supply this for a standalone LocoNet. Another function of the termination device is the connecting of pins 3 and 4 together. For a standalone LocoNet implementation, a small 12V power supply is used to provide power to the Railsync lines.

A number of devices, such as the PR3 can provide LocoNet termination.

A Utility Panel can also supply power on the Rail Sync lines.

Digitrax LT1

Main article: LT1

The LT1 is included with all Digitrax Starter Sets. It consists of a harness with 6 conductor Telco type wire and a male plug, a tester with a female 6 conductor jack and a protection resistor. The LT1 can be used to test LocoNet cables, as well as multifunction decoders. While it is basic, it can indicate the motor control is working, as well as functions.

Rail Sync

Low voltage RailSync signals are present on the cables. Check for them using the LT1. The two outer LEDs must be bright, and constantly lit. If not, work your way through the network until the offending cable is located.

For proper operation of the booster, all four LEDs should be lit.

This is not the same as a booster phase issue.

DCS100/DCS200 Command Stations

The NET indicator on the DCS100/DCS200 Command Station is a Red LED that displays information about what the Command Station sees on LocoNet. When your LocoNet is wired and operating properly, the NET indicator will be on and flickers any time a valid LocoNet message is detected by the Command Station. The following table explains the various patterns for this indicator:

Solid Red
ON, Blink OFF
Valid LocoNet Message detected.
LocoNet is possibly shorted
Blinking every half second
The command station is in Option Set mode.

LocoNet Repeater (LNRP)

For large complex layouts, Digitrax offers the LNRP LocoNet Repeater. It allows the creation of two LocoNets: One protected, one unprotected. The protected one is used to connect boosters, etc., while the unprotected network is used for throttles. This protects the layout from a network crash, often caused during throttle connect/disconnect operations.

The LNRP has diagnostic LEDs to help troubleshoot network problems.

LocoNet & RailSync Voltages

Main article: LocoNet and RailSync Voltages

If either voltage is low, the layout may experience several different symptoms.

  1. Difficulty turning on track power to additional Boosters.
  2. Throttles may not operate correctly or may have no display at all if they do not have a battery installed.
  3. Detection and/or Transponding may not operate correctly.

Use a good quality Digital Voltmeter (DVM) to help diagnose:

  1. If the 2 LocoNet data lines (pins 3 & 4, green/red) have voltage between 8V and 14V with no message traffic present. This confirms that the booster is outputting enough voltage.
  2. If the RailSync lines are OK. The two RailSync lines are a differential representation of the track digital signal, and are driven with a 22-ohm output impedance so as they are loaded the voltages will drop, indicating the current load. These two lines should not be connected together, and this will cause excess current draw and low voltages.

Differential means that if signal A is Positive, the corresponding signal will be Negative in polarity. This allows the pair to be summed together (A – (−B)). Since noise will be of the same polarity and amplitude, summing the two signals cancels any noise.

The Digitrax RJ12 LocoNet Wiring Standard

Digitrax UP5 Panel

In the instruction manual, it says "The RJ12 is the 6-pin version of the RJ11 connector with all pins loaded with conductors. This is the connector that Digitrax uses for LocoNet." At which point, your eyes start to glaze over and you go off into a trance. Now before you go into a coma, let's back up a bit. You're familiar with your telephone set and the cables and plugs that go into the telephone set.

On the previous page, we've shown you some of the Digitrax components that use these components. The LocoNet consists of the same type of wires and connectors - used in your telephone system - with one very important difference. Your telephone cables may have 2 or 4 small wires covered by that grey, black or white plastic insulation. The Digitrax LocoNet uses components that require 6 wires. Here's what this type of cable looks like. It's really not much different from the cable that goes into your telephone set.

The telephone/data communications industry calls this an "RJ12 6-wire standard". RJ12 components consist of 6-wire telephone cable, 6-wire male plugs and 6-wire female jacks. You can have many different combinations of these components.

  • Male plug to flat cable to male plug.
  • Male plug to flat cable to female jack.
  • Male plug to two female jacks - all in one plastic assembly.
  • Female jack to Female jack - all in one plastic assembly (sometimes colloquially called a gender-bender).
  • Female jack in a wall plate or two female jacks in a wall plate
  • Male plug to flat cable to two female jacks (I call this a double-female extension cord)

This is what some of these components look like.

If you have a Digitrax system, six wires are very important. Anything less and it will not work.

Here are the wiring standards, wire colours, functions, and pin-outs for the Digitrax RJ12 6-wire LocoNet. (If you're using Lenz, Atlas, NCE, or any other system, check your user manual.) Note the relationship between the Pin Number, the colour of the wire inside the cable, the function, and the voltage.

LocoNet Wiring Standards.jpg

If you look at the front of the male plug with the locking tab on top, you'll see that the White wire (Pin 1) is on the left, and the Blue wire (Pin 6) is on the right. If you look at the front of the female jack, you'll see that the White wire (Pin 1) is on the right and the Blue wire (Pin 6) is on the left.

The wires form two mirror images of three wire sets. This eliminates polarity and mating issues.

If you visually connect the male plug to the female jack, you'll see that the white wire of the male plug connects to the white wire of the female jack, the black wire connects to the black wire, the red to the red, the green to the green, the yellow to the yellow, the blue to the blue. This is sometimes referred to "Pin 1 to Pin 1, Pin 2 to Pin 2, Pin 3 to Pin 3, Pin 4 to Pin 4, Pin 5 to Pin 5, Pin 6 to Pin 6" wiring - or "Pin 1 to Pin 1" wiring to keep it short. It will help in troubleshooting if you always make sure that each coloured wire connects to its own colour. Also note that

  • The white wire (Pin 1) has the same function as the blue wire (Pin 6) - Rail Sync
  • The black wire (Pin 2) has the same function as the yellow wire (Pin 5) - Ground
  • The red wire (Pin 3) has the same function as the green wire (Pin 4) - LocoNet

A Loconet cable has two grounds and LocoNet lines, so the parallel communication lines reduce the effective loop resistance. This allows longer runs of cable. If a wire should break or create an intermittent connection, the network will still function.


The two outside wires, white and blue, each carry a copy of the master packets transmitted by the command station to the rails, are called RAIL SYNC. These two wires carry the Rail Sync as differential signals (one line is inverted in polarity). This method allows the two signals to be summed together at the receiver, cancelling any common mode noise in the signal. RAIL SYNC can drive a booster feeding a power district hundreds, if not thousands of feet from the command station.

RAIL SYNC also allows you to power low current power draw devices, such as LocoNet input sensors (utility panels such as the UP5) or utility throttles without internal power sources. Devices such as the UR92 Radio receiver draw too much current so they must be powered externally. Even so, it is advisable to power some Utility Panels with their own power supply.

The utility panels use diodes to power to the front and side jacks. As there is no Rail Sync present on those jacks, a booster cannot be connected to them. The external power supply allows more power to be supplied to the front and side jacks to power throttles. This power is local only, and is not supplied to other panels via the rear jacks, unless a link is installed (per Digitrax instructions.)

Benefits of the Cable Construction

Since the six conductors create a balanced cable, signal propagation is arranged in a manner to minimize RFI (Radio Frequency Interference), LocoNet transmissions should not cause problems with radio and TV reception. It also minimizes the susceptibility of LocoNet to EMI from power tools and radio transmitters such as wireless phones or garage door openers.

Making a LocoNet Cable

Making a LocoNet cable is a simple process. It can be done quickly and easily. The costliest part is the crimper required. Click on the link below for more information.

Main article: LocoNet/Making a LocoNet Cable

LocoNet Limitations

The limitations to LocoNet are:

  • Distance - May have a total parallel cable length of up to 2,000 feet, with no point-to-point length exceeding 1000 feet.
  • Max number of devices? - That depends on the current draw in the LocoNet but that can be quite a technical subject. For modellers who use Digitrax systems at home, they will never reach that limit. However, if you belong to a MR Club with a large layout and many throttles in use, you can experience some problems.

RJ Information

Standard Use Positions
Authority Plug Width Jack Width
RJH Telephone Phone Hand Set 4p4c FCC 0.299" 0.355"
RJ11 Telephone Phone Single Line 6p2c FCC 0.375" 0.383"
RJ14 Telephone Phone Single Line 6p4c FCC 0.375" 0.383"
RJ12 LAN/Printer network 6p6c Industry 0.375" 0.383"
RJ25 Same as RJ12 but for stranded cable 6p6c Industry 0.375" 0.383"
RJ45 LAN/Data network 8p8c Industry 0.492" 0.459"

RJ stands for Registered Jack - as in telephone jack - which were registered with the Federal Communications Commission (FCC) by the telephone industry when plastic modular components were developed in the 1950s/60s. As data communications technology developed the telecommunications industry added to these standards. The RJ standards do not refer to the physical size of the male plugs or the female jack. They refer to the way the jack is to be wired and what the wiring is to be used for.

To confuse things even more, the RJ standards specify the number of conductors (wires) going into the plug or jack and the number of positions available in the plug or jack to anchor these wires to. For example, the RJ12 LocoNet plugs and jacks we use are specified as RJ12 6p6c. That is, 6 positions are available to anchor the wires (the 6p). Six conductors (wires) can be wired into the plug or jack (the 6c). And all of this wiring is to be used for a Local Area Network (LAN) - which we call the LocoNet.

The columns for "Plug Width" and "Jack Width" aren't part of the standards. To remove some confusion, I took my digital caliper and measured these plugs. RJ11 RJ14, RJ12, and RJ25 have the same Plug and Jack Widths. Only the RJ12 for solid wire and the RJ25 (stranded wire) have the number of cables/positions we need for LocoNet. Failure to match the connector to the wire type will result in reliability issues later.

Parts Suppliers

Here is a listing of websites where you can order pre-made cables. The downside is that you're stuck with whatever lengths you find. There is also a list of suppliers for bulk cable, connectors, crimpers, and end pieces. This will allow you to make cables of any length.

Premade Only:


Supplier Name Shiping Locations Types of Products
-- C   C   C--
Cable Wholesale US Based, International Shipping Bulk cable, premade cable
-- D   D   D--
DigiKey US Based, International Shipping Bulk cable, premade cable


Supplier Name Shiping Locations Types of Products
-- A   A   A--
Action-Electronics ? Cable Connectors
-- M   M   M--
My Cable Shop US Based, International Shipping Cable Connectors

LocoNet Licences

Digitrax maintains a list of Licencees of Loconet

DCC Systems Employing LocoNet

  1. Digitrax, the owner and creator of LocoNet
  2. Digikeijs, a Dutch manufacturer of Loconet Products including command stations and occupancy detection devices
  3. Uhlenbrock
  4. Fleischmann
  5. Massoth
  6. PIKO 55044 LocoNet Convertor Box for the PIKO SmartBox, also compatible with ESU EcOSLink

Some also produce LocoNet compatible hardware

Software Licencees

A number of companies have licensed the LocoNet software. JMRI is an example of a LocoNet Licensee.

Do It Yourself Solutions for LocoNet Interfaces

A few solutions exist for "roll your own" interfaces.


LocoLinx on Arduino UNO with FremoLNShield

Supports Hardware Handshaking. Requires a LocoNet Shield

Webpage with more information.

LocoLinx on Arduino Duemilanove with Loconet Shield on Proto Shield

This one is outdated and may be difficult for find

Suports hardware handshaking via the CTS line. Incorporates a genuine FTDI USB IC, less issues with drivers. (The LocoBuffer USB also uses this IC.) Duemilanov

Webpage with more information.

There is more information on LocoNet interfaces available on the LocoNet over TCP webpage.

ArLoco from ARCOMORA

The ArLoco is an Arduino Shield 16 (UNO) or 58 (MEGA2560) channel feedback encoder with LocoNet interface.

Supports LocoNet-T and LocoNet-B. Has two LocoNet RJ12 jacks.

For more information see their website.

Model Railroading with Arduino LocoNet Interface

This site has details on a LocoNet interface. Construction details are here.

There are a number of other projects on that site as well.

Iowa Scaled Engineering

DCC Decoder Shield for Arduino

The ARD-DCCSHIELD is an optoisolated interface shield for connecting an Arduino (as a decoder) to a model railroad DCC control system. It cannot act as a command station.

NMRA Digital Command Control (DCC) Library

This library allows you to interface to a NMRA DCC track signal and receive DCC commands.

The library currently supports the AVR ATTiny84/85 & ATMega88/168/328/32u4 and Teensy 3.x using the INT0/1 Hardware Interrupt and micros() ONLY and no longer uses Timer0 Compare Match B, which makes it much more portable to other platforms.

Download the NMRADCC library from GitHub.

See Also



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