SKU: 1000

    The A4X is four function HO-scale "drop-in" style mobile decoder for Atlas, Athearn, Kato, etc. locomotives.

    Examples include the following:


    • F59PHI
    • F3


    • RS-1/RS-3/RS-11
    • C424
    • GP7


    • GP35

    See the installation pages for a full list of compatible engines!

    If you need more than four total lighting functions, or are using 1.5V bulbs, you should consider the A6X.

  • Back EMF Load Compensation:
  • Provides superior slow speed control and high performance under load.

  • Quiet Drive:
  • Super-quiet motor control for "buzz" free motor performance.

  • DC Mode:
  • Decoder will automatically detect DC power. You can also configure how your lighting effects function on DC.

  • RailCom®:
  • This feature allows the decoder to talk to the command station. RailCom supports expansion for new features.

  • Variable Momentum:
  • Allows you to make custom acceleration and deceleration curves.

  • LED Support:
  • This product does not require external resistors when connecting LED's.

  • Incandescent Bulb Support:
  • This decoder can be used with 12 Volt bulbs.

  • Function Remapping:
  • Buttons 0 through 12 may be used to control the lighting functions of this decoder.

  • Programmable Lighting Effects:
  • Choose from 20 separate user-programmable lighting effects!

  • Dimmable Brightness:
  • Configure multiple different brightness levels for your LED's or incandescent bulbs.

  • Decoder Lock:
  • Feature which prevents accidental/unwanted programming while activated.

  • Airwire™ Compatible:
  • Fully compatible with Airwire™ operation.

  • User-Loadable Speed Tables:
  • Configure custom speed curves and set speed limits.

    Interface Type
    Dimensions (L x W x H): 2.85" x 0.682" x 0.138" or 72.39mm x 17.32mm x 3.51mm
    Scale: HO Scale
    Continuous/Peak: 1.0/2.0 Amp
    Total Functions: 4
    Function Rating: 100 mA
    12V Outputs
    LED Outputs
    Decoder Variant (Harnessed versions etc.):

    Decoder Literature

    Download A4X.pdf (592.71 KB)

    Comprehensive Guides

    Keep-Alive® Wiring Diagram
    A4X KA Wiring Diagram
    Keep-Alive® Ready Version

    One Year Goof Proof Warranty

    All decoders are covered by a one year goof proof warranty. Please return in a small box.
    You MUST register the failed decoder on our website at tcsdcc.com/warranty
    Follow the instructions on the website before returning any decoders to TCS.