Atlas Wiring Glossary

Acute Frog - The two frogs in a crossing which are less than 90°.

Ammeter - A device which is used to measure amperes.

A.C. (Alternating current) - An electric current that reverses
direction in a circuit at regular intervals. Ordinary house current
is alternating current.

Ampere - A measurement of current flow, example one ampere of current
through an ohm resistor will give one current.

Block - An electrically isolated track section that can be
independently operated.

Brass - A yellow metal alloy consisting of copper and zinc, making it
a good electrical conductor.

Cab - A power pack used to control model trains.

Cab Control - A method of wiring a layout to allow control of
electrical blocks, which may be passed back and forth between cabs.

Circuit - A closed path through which an electrical current may flow.

Common Lead - A wire from the power supply to the common, or ungapped rail.

Common Rail - The rail in a model railroad layout without electrical gaps.

Common Rail Wiring - A method of wiring your layout where one rail
has electrical continuity throughout the layout.

Connector (ATLAS Item #205) - A device manufactured by Atlas to turn
electric power on or off to track sections or accessories.

Controller (ATLAS Item #220) - An electrical device manufactured by
ATLAS, which provides the proper operation of reversing loops and

Control Rail - The rail in a model railroad layout which has electrical gaps.

Crossing - The point where two railroad tracks cross each other
without joining.

Current - Electricity flowing in a circuit. Current flows from
positive (+) to negative (-); comparable to water flow through a pipe.

Cycle - One complete period of the reversal of an alternating current
from positive to negative and back again.

D.C. (Direct Current) - An electric current that flows in one direction only.

Dogbone - A configuration of model railroad track which looks like a dogbone.

Double Pole Double Throw (DPDT) - An electrical switch that can be
adapted to reverse the flow of electric current. Many DPDT switches
have an "off" position in the center. (a.k.a. - Two single pole
single throw switches mounted and operating together.)

Double Track Wye - A track configuration in which two parallel tracks
both create wyes. Traversing the complete double track wye will
result in the train running on the opposite track.

Drill- To switch a train or cars from one track to another.

Flange - The protruding edge on a wheel which acts as a guide against the rail.

Flux - A paste used in soldering to assist the molten solder to flow freely.

Frog - The location where two rails cross in a turnout or crossing.

Gap - An electrical break in a rail. In a common rail system, the gap
would be in the control rail. The exception would be if there is a
reversing section or wye; in which case the gap would be in both

Gauge - The distance between the rails of a railroad track, measured
from the inside of the railheads.
Real Railroad (Standard) = 4' 08 1/2"
N Scale Railroads = 9mm
HO Scale Railroads = 16.5mm
O Scale Railroads = 31.8mm

Insulated Joiner - A plastic clip that joins two sections of track
mechanically, but isolates them electrically.

Insulated Frog - A frog that is electrically isolated from the rails.

Ladder Track - The track in a ladder yard from which all other track
Layout - A model railroad.

Main Line - The primary railroad track that carries through traffic.

Multi-meter - An electrical instrument consisting of an ammeter,
ohmmeter and voltmeter, all contained in one casing.

NMRA - National Model Railroad Association
4121 Cromwell Road
Chattanooga, TN 37421
The NMRA sets standards for the compatibility of model railroad
equipment and is dedicated to the promotion and improvement of the

Nickel Silver - A silvery colored metal alloy consisting of copper,
zinc and nickel. A good electrical conductor.

Ohm - A unit of electrical resistance.

Ohmmeter - A device used to measure ohms. Also used to find a shortcut.

Passing Siding - A double-ended siding, long enough for two trains to
pass one another.

Points - The moving portion of a turnout, usually two connected short
rails in a turnout that move to change a train's route.

Polarity - The direction a current moves through a circuit.

Power - The work done by an electrical current. the unit of power is the watt.

Power Pack - An electrical device that plugs into a household outlet
and converts 110 volts AC to 12 volts DC. HO and N scale model
railroads use 12 volts DC. (ATLAS Item #310)

Prototype - The actual full-sized object a model is patterned after.

Rail Joiner - A small metal clip used to join two sections of track
mechanically and electrically.

Rectifier - An electrical device which converts AC current to DC current.

Relay - A power operated electrical switch. (See also, "Snap-Relay")

Remote Control Turnout - A turnout (switch) whose points are
electrically operated from a remote position.

Resistance - The property of a conductor which limits or opposes the
passage of an electrical current. The amount of resistance is
measured in ohms.

Resistor - An electrical device which limits the passage of an
electrical current. The value of a resistor is expressed in ohms.

Reverse Loop - A section of track that goes around in a circle and
comes back on itself and is joined by a turnout at this point. A
reverse loop can resemble a balloon on the end of a string, or, in
more complex plans, reverse loops/reversing sections may be less

Rheostat - An electrical device used to vary the amount of voltage
delivered to a motor, thus acting as a speed control. Also called a
variable resistor.

Scale - The proportional size of model railroad items compared to the
real thing (prototype).
N Scale - 1/160th the size of the real item
HO Scale - 1/87th the size of the real item
O Scale - 1/48th the size of the real item

Selector - (ATLAS Item #215) An Atlas electrical device that enables
the operation and control of two trains at the same time.

Short Circuit - A usually unintended flow of current between two
points, bypassing the normal electrical circuit.

Siding - A side or secondary track, also called a "spur".

Single Pole Single Throw (SPST) - A simple "On-Off" electrical switch.

Snap-Relay - (ATLAS Item #200) A DPDT relay with actuating mechanism
driven by a momentary-power, twin coil solenoid.

Solder - A soft, wirelike metal comprised of tin and lead, which,
when melted, is used to join two pieces of metal or wire.

Soldering Iron - A device used to melt solder and accomplish the act
of soldering.

Solenoid - A cylindrical coil of insulated wire in which an iron core
is made to move back and forth by a flow of electric current.

SPDT - An electrical switch that can allow power to be supplied to
any two components from one source.

Spur - See Siding.

Stock Rail - The two outer rails in a turnout.

Stub Track - A track that comes to a dead end. Used for storing
locomotives and/or cars, or to lead to a structure on your layout.

Switch - 1. A device to route train wheels from one set of rails to
another by means of moveable points. Also called a "turnout". 2. An
electrical device that routes, reverses or interrupts the flow of
electrical current.

Switch Machine - A device, either manual or electrical, (remote),
connected to the points of a turnout to change the setting of the

Tender - The car directly behind a steam locomotive that carries the
fuel and water for the engine.

Terminal Joiners - Rail joiners with wires affixed. Used to conduct
electricity from the power pack to the rails.

Terminal Section - Also known as terminal track. A section of model
railroad track with attachments for wire. Used to conduct electricity
from the power pack to the rails. Terminal sections may be straight
or curved.

Terminal Strip - A series of screw or clip-on wire terminals mounted
on a strip of insulating material.

Throwbar - The bar connecting the two point rails in a turnout.

Tin (or Tinning) - In soldering, a thin coat of solder on the tip of
a soldering iron, on the surfaces of two pieces of metal to be
joined, or on a piece of wire.

Toggle Switch - One of many variations of electrical switch. Other
types of toggle switches include double pole, double throw; single
pole, single throw. etc.

Track Section - See "Block"

Transformer - An electrical device which either increases or, more
commonly, decreases electrical voltage.

Trucks - The device beneath railroad cars or locomotives that hold the wheels.

Turnout - A section of track with moveable rails to divert a train
from one track to another. Same as a switch; that point where two
diverging tracks come together.

Twin - (ATLAS Item #210) An Atlas electrical component consisting of
two double pole, double throw reversing switches wired in parallel.

Volt/Voltage - A unit of electromotive force, comparable to water in
a water tank/tower.

Voltmeter - A device used to measure volts.

Watt - A unit of work done by an electrical current (power).

Wye - A triangular shaped track arrangement, using three turnouts,
where trains may be reversed. Can also refer to one turnout with two
curved diverging routes instead of in a straight and one curved
route, as is commonly found.

X-Sections - A section of track, electrically isolated, used to
temporarily "x"-tend the length of adjacent sections (blocks).

Yard - A group of side tracks where railroad cars are stored or where
trains are made or broken up prior to or after a run.

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