If you found yourself on this page and are wondering what the difference is between AC, DC, and DCC, this may help. 

DC Power
DC (Direct Current) is the conventional method of powering most N, HO, On30, and G Scale trains.  The power pack supplies varying levels of voltage to the rails which, in turn, changes the speed of the locomotive.  To change direction, the polarity on the rails is simply reversed.  This works reliably and is fine for less complicated layouts and with few trains.  However, since you are really controlling power to the rails, any trains on the same rails will go in the same direction and cannot be controlled independently (ie - one cannot be stopped while the other is moving).  To work around this, track blocks can be created so that power to these isolated sections of track can be independently controlled.  This can lead to some complicated wiring and some confusing operation.  However, it can and is done.

DCC Power
This is a newer approach to model railroading and in a nutshell, works like this.  The concept of DCC (Digital Command Control) is that you are now directly and independently controlling individual locomotives anywhere on the layout.  To make this work, each locomotive must have an installed computer chip known as a decoder.  In contrast to how DC works, in DCC a constant voltage is applied to the rails at all times.  To make an engine move, your throttle and command station are used to send digital instructions via the rails to your locomotives.  Some of the benefits are that you don't need to worry about what block the locomotive is occupying, locomotives can act independently of one another, and with most decoder equipped locos, you can turn lights on and off.  Many are now also coming with sound capabilities that can all be controlled independently.  Because you don't need all of those blocks, wiring also becomes simpler.  Keep in mind that you cannot control DC engines on a DCC layout.

AC Power
Now, many O Scale layouts work on a 3-Rail system that is AC powered.  AC (Alternating Current) is different from DC in that the direction of current quickly changes direction at a high frequency.  Because of this, motors designed to be used on AC will not work with DC.  They need a different power supply.  Bachmann, Lionel, and MTH are examples of trains that require AC Power supplies.

Power/DCC/Electrical

Bachmann - Operating Car Remote Control Unit - Williams™

Bachmann Operating Car Remote Control Unit -  Williams™
Item #: 160-47999
MSRP: $69.95
You Pay: $44.66
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Bachmann - Plug-and-Play Sound Module -- Fits Spectrum® Baldwin 2-4-4-2 - On30

Bachmann Plug-and-Play Sound Module -- Fits Spectrum® Baldwin 2-4-4-2 - On30
Item #: 160-44952
You Pay: $75.49
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Bachmann - E-Z Command 1-Amp DCC Decoder -- With Wire Harness 9-1/2 x 25 x 5mm - HO

Bachmann E-Z Command 1-Amp DCC Decoder -- With Wire Harness  9-1/2 x 25 x 5mm - HO
Item #: 160-44925
MSRP: $51.00
You Pay: $32.56
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Bachmann - E-Z Command Automatic Reversing Loop Module

Bachmann E-Z Command Automatic Reversing Loop Module
Item #: 160-44912
MSRP: $99.00
You Pay: $63.20
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Bachmann - DCC 5 Amp Power Booster - E-Z Command®

Bachmann DCC 5 Amp Power Booster - E-Z Command®
Item #: 160-44910
MSRP: $429.00
You Pay: $267.78
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Bachmann - E-Z Command DCC Systems -- Walk-Around Companion Panel Connector w/Connector Wire

Bachmann E-Z Command DCC Systems -- Walk-Around Companion Panel Connector w/Connector Wire
Item #: 160-44908
MSRP: $60.00
You Pay: $38.30
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Bachmann - 10' Terminal Extension Wire Red HO

Bachmann 10' Terminal Extension Wire Red HO
Item #: 160-44498
You Pay: $7.98
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Bachmann - Power Pack w/Speed Controller - G

Bachmann Power Pack w/Speed Controller - G
Item #: 160-44217
MSRP: $99.00
You Pay: $63.20
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Bachmann - Power Pack w/Speed Controller N/HO/On30

Bachmann Power Pack w/Speed Controller N/HO/On30
Item #: 160-44211
MSRP: $89.00
You Pay: $56.82
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- #4 Right Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- #4 Right Hand - HO
Item #: 160-44140
MSRP: $81.00
You Pay: $51.71
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- #4 Left Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- #4 Left Hand - HO
Item #: 160-44139
MSRP: $81.00
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- Single-Crossover #6 Right Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnouts -- Single-Crossover #6 Right Hand - HO
Item #: 160-44138
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout -- Single-Crossover #6 Left Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout -- Single-Crossover #6 Left Hand - HO
Item #: 160-44137
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Bachmann - Decoder-Equipped Nickel-Silver Turnout - E-Z Track® -- #6 Right Hand - HO

Bachmann Decoder-Equipped Nickel-Silver Turnout - E-Z Track® -- #6 Right Hand - HO
Item #: 160-44136
MSRP: $95.00
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Bachmann - Decoder-Equipped Nickel-Silver Turnout - E-Z Track® -- #6 Left Hand - HO

Bachmann Decoder-Equipped Nickel-Silver Turnout - E-Z Track® -- #6 Left Hand - HO
Item #: 160-44135
MSRP: $95.00
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Wye - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Wye - HO
Item #: 160-44134
MSRP: $81.00
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Right Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Right Hand - HO
Item #: 160-44133
MSRP: $81.00
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Left Hand - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout -- #5 Left Hand - HO
Item #: 160-44132
MSRP: $81.00
You Pay: $51.71
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout - HO
Item #: 160-44131
MSRP: $68.00
You Pay: $43.41
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Bachmann - Decoder-Equipped Nickel Silver E-Z Track® Turnout - HO

Bachmann Decoder-Equipped Nickel Silver E-Z Track® Turnout - HO
Item #: 160-44130
MSRP: $68.00
You Pay: $43.41
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Bachmann - Interior Lighting Kit w/Wire pkg(2)

Bachmann Interior Lighting Kit w/Wire pkg(2)
Item #: 160-42240
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Busch Gmbh and Co Kg - Building Light -- 14-16V pkg(2)

Busch Gmbh and Co Kg Building Light -- 14-16V pkg(2)
Item #: 189-4280
MSRP: $4.99
You Pay: $4.22
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Bachmann - E-Z Command Dynamis Wireless DCC System IR Rx

Bachmann E-Z Command Dynamis Wireless DCC System IR Rx
Item #: 160-36509
MSRP: $54.00
You Pay: $34.47
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