Digitrax Signal System Glossary of Frequently Used Terminology

These terms are related to the Digitrax Signaling System

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z NUMBERS

-A-

Address, Decoder: a number assigned by the user to a particular mobile or stationary decoder. The DCC system uses the decoder address to send commands to the appropriate loco or accessory. In the case of signals, stationary decoder addresses are used.

Address Range: each system has a certain number of addresses that it can handle. Basic DCC systems usually handle between 6 and 16 addresses. Advanced systems usually handle between 99 & over 9000 addresses and Professional systems almost always go to 9000 or more addresses.

All live turnout: a turnout where throwing the turnout does not change the rail polarity. Also called non-power routing turnouts.

Ampere, amp(s): the unit of measure for electrical current used or provided by an electronic device. The current draw of most HO can motors is between .5 and 1.5 amps. DCC boosters usually provide between 2.5 & 10 amps. This means that in HO scale you can run between 4 and 6 HO locomotives on a 5 amp booster.

Aspect: a combination of lights or positions on a railroad signal which has a defined meaning. This meaning is the signal's indication.

-B-

-C-

Closed: the position of a turnout that is set so that the routing is through the straight leg or set for the main line.

Command Station: Each system has one Command Station that generates the DCC packets that tell the decoders what to do & produces Rail Sync so that all the devices you attach to LocoNet work together. With the Digitrax System you have a choice of several command stations to allow you to tailor your system to meet your needs. In an effort to keep the price down, we have chosen to combine command station functionality with other system hardware components. The Challenger Command Station is included in every DB100 series booster. The DT200 Command Station/Throttle is used as the command station in the Big Boy Starter Set. The DCS100 Command Station/Booster is the command station for the Chief Starter Set.

Common Rail Wiring: A wiring system in which one side of all the track power supplies are connected. The common rail concept simplified block wiring in conventional DC systems, but is not recommended for new layouts installing DCC wiring. (see Direct Home Wiring).

Configuration Variables (CV's): these are special storage locations or "pigeonholes" in your decoders. By programming various CV's, you can control each decoder's performance characteristics. CV's store information like the decoder's short address, long address, start voltage, mid-point voltage, loadable speed tables and many more. Once you have programmed these characteristics, the decoders "remember" them until you change them again. The NMRA “Standard and RPs” define the usage of each CV.

-D-

Daisy chain: a wiring plan in which each device may be connected through other devices to the controller.

DCC: Digital Command Control. On the most basic level, DCC encompasses systems and products that are interoperable with other manufacturer’s equipment which follows currently accepted DCC industry norms and practices. (The NMRA’s DCC “Standards and RPs” are a part of these norms and practices). In addition, DCC includes other related technologies that are designed to enhance and extend the basic capabilities.

DC or Direct Current: An expression used to describe an electrical wave form in which the voltage remains more or less at a value above or below 0 volts. The wave form used by most model railroad locomotives. Sometimes referred to as Analog.

Decoders, Stationary (Accessory) : the electronic device for the switches or other accessories that receives the signal from the command station through the track, decodes it & tells the switch/accessory what to do.

Detection section: a section of track gapped on one or both rails and connected to an occupancy detector.

Direct Home Wiring: A wiring system in which the DCC booster powers each rail through an individual conductor or wire. Each booster is wired to it's own power section and there is no common connection between boosters. This is the Digitrax recommended wiring system.

-E-

Event driven: a strategy for using a network's communication resources that sends traffic only when devices attached to the network need to communicate. LocoNet is an event driven network as opposed to a polled system which requires that each device communicate with the master in turn.

Exact feedback: the method of using a number of switches or sensors to determine the exact position or state of a turnout or other device.

-F-

Function cell: a group of electronic components within a stationary decoder that controls the logic for a pair of decoder inputs and outputs. Used to operate local routes.

-H-

-I-

Indication: the meaning given to a particular signal aspect.

-K-

-L-

LAN: Local Area Network.

LED: Light emitting diode. Many locomotives use LEDs for headlamps and other loco lighting. They do not generate any heat but their lighting characteristics are not as "crisp" as incandescent bulbs.

Local route: the operation of a number of function cells within a single stationary decoder independent from the command station.

LocoNet: Digitrax's powerful communications network especially designed for model railroad operation.

-M-

Manual block system: prototype train control system where by trains run from block station to block station. Trains require explicit authority to enter each block. Also used as the backstop method if an automated signaling system fails.

-N-

Nested route: a route that is part of another route. Digitrax systems can handle nested routes.

Non-power routing turnout: a turnout where throwing the turnout does not change the rail polarity. Also called all live turnouts.

Non-retriggerable: a stationary decoder function cell is non-retriggerable if it must complete its current output action before accepting a new input.

-O-

Occupancy detector: a device that senses the presence of rolling stock on a section of track and provides feedback to the system. Detectors are not covered by the NMRA’s “Standards or RPs”.

Ohm(s): the unit of measure of electrical resistance.

Operating current: the current draw, stated in amps, used by a loco, including its motor, lights and other accessories when operating continuously under normal continuous at full load. This measurement is important for determining which decoder to install in the loco.

-P-

Peer-to-peer: a network communications protocol where messages between devices are not managed by a central mediator. LocoNet is an event driven peer to peer network.

Polarity: the two directions of current flow, plus (+) and minus (-), in any electrical circuit. Mismatches in track polarity create reversing problems.

Positive feedback: the method of using a switch or sensor to determine one of the two possible positions of a turnout or states of a device.

Power bus: the main wires that carry power from the booster to provide power feeds to the power district. The power bus is very important for DCC layouts since the DCC signal is carried on the power to the layout. If there is not good power everywhere on the layout, then the locos will not "see" the DCC signal.

Power district: the power wiring, components and equipment attached to that wiring, driven by a single properly isolated booster.

Power routing turnout: a turnout where only the route selected is live and the rail polarity changes when the turnout is thrown.

Power sub-district: a subdivision of a power district. Usually controlled by a power management device like a PM42.

Power Supply: a transformer that provides power to the DCC system. The transformer is not usually included with the DCC system.

-R-

Reverse loop or reversing section: any track layout that allows a loco to enter and exit on the same rails while moving in the same direction. This creates a track polarity mismatch at one end or the other of the track section which must be corrected in order for the loco to continue moving.

RJ12: standard type of telephone style plug and socket used for six conductor cable.

Route: a group of turnouts and their specified positions that will be triggered by the activation of a single "TOP" switch address to a specified position.

-S-

Security element: the plant including track, associated with any reporting, interlocking and/or signaling for that track. Also called simply "plant."

-T-

Throttles: Throttles are input devices that tell the Command Station what you want the decoders to do. You can have many throttles on your system. The number is determined by the capabilities of the Command Station you are using. You can also use a computer to create "soft" throttles. Sometimes DCC throttles are also called "Cabs."

Thrown: the position of a turnout where the routing is through the curved leg or set for the diverging route.

Track feed: a short section of wire that connects the power bus to the track and supplies track power.

Transponder or Transponding Device: A device used in a locomotive, car or caboose that sends identification and position information about the unit to the LocoNet system via transponder detectors. Digitrax transponding devices are not unique to DCC and can be used on many other power formats.

Transponder Detector: A device used to receive information from transponding devices on the layout and transmit that information to the LocoNet system. Digitrax transponder detectors are not unique to DCC and can be used on may other power formats.

Trigger: an event that causes an action to occur.

-U-

-W-

Whole layout common rail: layout wiring method where power districts and their boosters are connected electrically by a common rail or common power bus return wire.

-Z-