I don't claim to be an expert on anything relating to railroads or modeling, and I'm always running into words, phrases, abbreviations, and acronyms that are new to me. If you are like me, confused by some of the stuff you see in articles and on eBay, maybe this will help you. You can click on many of the pictures to see a larger image.

Beep

Beep is a nickname that comes from "Baby Geep" (GP engine). A beep is a drastically shortened engine that resembles a GP. There are no beeps in the real world--beeps are just toy/model engines. Click here to see a size comparison.

Big Mo

I saw that MTH has a number of freight cars with this "roadname" but I couldn't find out anything about it, so I finally called MTH and asked. Apparently there was a guy who set up an MTH layout in a semi-trailer and drove around to shows with his "big mobile" layout. He was an MTH vendor, and these items are special runs for him. So this isn't a real roadname.

consist

Pronounced KAHN-sist. This is basically everything that the engines are pulling. A switcher will work in a yard to put together a consist of freight cars, taking into account their destinations and the order in which they will be dropped off. A passenger consist is made up of coach cars, dining cars, baggage cars, sleepers, and many other types of cars found on passenger trains.

highrailer

Definition 1: An automobile or truck that has been modified so that it can also run on train track. Usually there is a mechanism to let the vehicle switch between using its tires and using the rail wheels. Some people don't consider vehicles that are permanently modified for railroad use only to be true highrailers.
Definition 2: A railroad enthusiast who mixes scales or isn't overly concerned with accurate detailing when building layouts and operating trains. Often just using 3-rail track is enough to warrant the label. Sometimes it is used in a perjorative sense, but most highrailers are proud of the label and find their way of building and operating model trains to be the most enjoyable.

ITAD

For MTH, ITAD means "infrared track activation device." This is a device that sits next to or is connected to the track and uses an infrared sensor to detect a passing train. The ITAD can be used to control trackside accessories and lights. See also TAD.

knuckle coupler

The knuckle coupler is the car-connecting mechanism found on nearly all post-WWII O and O-27 trains. It is modeled after the real-life couplers found on nearly all North American trains as well as those in many other countries. Good knuckle couplers are metal, able to support a lot of weight without opening, and can be remotely controlled, usually by an electromagnet under the center rail.

LLC

In 1995, a controlling interest in Lionel Train, Inc. was sold by Richard P. Kughn to a consortium of investors. The company was renamed Lionel LLC. Lionel-brand items produced in the 1996-2006 era are often referred to as LLC items. See also MPC and LTI.

LTI

When General Mills sold its rights to the Lionel brand name in 1985, it was purchased by Richard P. Kughn of Detroit, Michigan. Kughn's company was called "Lionel Train, Inc." Lionel-brand items produced between the years of 1986 and 1995 are referred to as LTI items. See also MPC and LLC.

MIB

This is an eBay abbreviation that means "Mint In Box." Something labeled MIB should be what you would expect had it been shipped straight from the manufacturer.

MOW

Maintenance of Way. There are many kinds of rail cars that are owned by a railroad company to inspect and repair track, ties, ballast, etc. These special railroad cars are called MOW equipment or MOW cars. Examples of MOW cars are cranes, inspection cars, snowplows (shown at right), clearance cars, and many others.

MPC

MPC stands for "Model Products Corporation." When General Mills bought manufacturing and distribution rights to Lionel train products in 1969, it continued to produce Lionel trains and accessories through its MPC subsidiary. Lionel-brand items produced between 1970 and 1985 are commonly referred to as MPC items. See also LTI and LLC.

MU

MU stands for "multiple unit" and refers to a type of passenger car that has its own motor. These can be linked together to form a train of identical cars without any separate engine being needed. Many commuter trains and nearly all subways use MUs since MUs can easily be run in either direction without having to be turned around, they are efficient, and they can be broken up or expanded as needed.

NIB

This is an eBay abbreviation that means "New In Box." Something labeled NIB should never have been used after it was shipped from the manufacturer.

NR

This is an eBay abbreviation that means "No reserve." That is, there isn't a price that the seller has set up as the lowest acceptable bid.

O-27

O-27 is a type of O gauge. It became popular after WWII as a cheaper and smaller version of O gauge railroading. O-27 track is 3-rail and is the same gauge as standard O, but the track isn't as tall and the track pins are smaller. The reason O-27 got its name is because O-27 curves form a 27-inch circle instead of the 31-inch circle for standard O. Later companies started making O-27 track with curves of 42 inches and larger. This track is still called O-27 because of its height and pin size. You can combine O-27 and standard O track by shimming up the O-27 track and by either crimping the standard O track so that the O-27 pins are tight or else by slightly opening the O-27 track so the standard O pins will fit.
As far as scale goes, O-27 usually means something smaller than standard O scale. "O-27 scale" is generally thought to be about 1:64 (S scale) instead of 1:48 (O scale), but you'll find a lot of variation. O-27 engines and cars are often shortened and out of proportion so that they will operate on the tight O-27 curves. Remember, O-27 is meant to be functional rather than a true scale model. So you can build a great-looking O-27 layout, but a purist may turn up his nose while pointing out some inaccuracies in size and proportion. Ignore him.

OB

This abbreviation is sometimes used on eBay to mean "Original Box." If something is listed as "Used OB" or "New OB" you are being told that the item will be sent in the box that came from the manufacturer.

reefer

This is just an abbreviation for "refrigerator car." A reefer looks a lot like a box car, but it is tightly sealed and either has an ice container (old style) or an electrical refrigerator unit (modern style).

RiteTrax

This is what MTH called RealTrax before Atlas sued them for trademark infringement. MTH briefly explained the change in the December 1998 issue of their club newsletter "Crossinggate."

scale

Scale refers to the size of the model relative to its real-life counterpart. The most accurate way to describe scale is in proporations, such as 1:48 (one foot in the model equals 48 feet in real life). Some scales have names: O scale is 1:48, S scale is 1:64, HO scale is 1:87. You have to be a bit careful, however, since sometimes people and companies take liberties with scale names, and there are often differences between the meaning of scale names in different countries. The biggest problem is with O scale, since historically so many different scales were run on the same track. Sometimes people say "O scale" when they mean "O gauge." Note that scale is different from gauge, which is a measure of how wide the track is. I suppose if you wanted to, you could take an HO scale boxcar, swap out its axles for longer ones, and run it on O gauge track. Likewise, you could take an O scale boxcar, probably get it to balance on small axles, and run it on HO gauge track.

service station set

Lionel occasionally would produce items that would be sold only to Lionel Service Stations (repair/maintenance shops). Items range from clocks and tools to engines and train sets. An SSS is an engine and consist that was available only to and/or through an authorized Lionel Service Station. Greenberg's Guides list these as SSS (service station special).

TAD

For MTH, TAD stands for "track activation device." This is a device that slips under standard tubular track and detects when a train is passing. The weight of the train pushes the TAD down and compresses a switch. The switch can then control trackside accessories or lights. See also ITAD.

truck

The truck is the part of a railroad car that holds the axles, wheels, and suspension. Trucks on model trains sometimes include the coupler (the image on the right shows a real truck rather than a model, so the coupler is not part of the truck). On models, the best trucks are die-cast metal with spring suspension, metal axles, metal wheels, and metal operating couplers. Cheap trucks are made with all plastic, including the axles and wheels, have no springs, and couplers are either non-operating or manual operation only. Some trucks are a mix of plastic and metal, such as plastic trucks with metal wheels. On 2-rail systems the wheels have to be electrically insulated from each other, but on 3-rail you want them be metal and to form a circuit. Plastic wheels and axles will work fine for making the cars go around the track, but they won't allow accessories to detect their presence on the track and they won't trigger the anti-derail feature of track switches. Lightweight, all-plastic cars also derail much more readily when the train is backing up or when there is pressure during a coupling in the train.

W sign

There are train signs that consist of the letter W. The W stands for "whistle," and an engineer is supposed to sound the train's whistle before passing such a sign.

wye

A wye is a track configuration that allows a train to reverse direction. The train turns around the way a car would turn around using a driveway. Creating a wye requires at least three switches. There are many ways that this can be done, and the track doesn't have to have a clean "Y" or triangle shape to be called a wye. In the picture on the right, we see the simplest configuration. A train coming from the left would switch in one direction, move past the second switch, back up on the vertical track past the third switch, and then go forward on the last part of the track, heading "west." The wye can be used to reverse direction from any of the three tracks coming into the wye, not just the one on the left. Since any type of switch can be used, and since the track connecting the switches can be any shape and length, sometimes a wye can be hard to notice on a complex layout.

wye switch

A wye switch is a switch where both tracks are curved away from the center line. Most common track switches have a curve coming off of a straight piece. Although any three switches can be used to make a wye, a wye switch makes the layout simpler and easier to build. Wye switches can also be used in yards and other places where two tracks must split out from one, not always just to build a wye.