Decoder Tester

$149.95 Buy Now

This premium decoder tester provides an easy way to test and program your decoder prior to installation, or perform diagnostics.

Included on this tester:

  • 8x LED's (with built-in resistors) for testing light functions
  • 28mm WOWSpeaker built in for sound decoders
  • 5-pole, KATO motor
  • On-board power supply for use with NEM651 decoders

The TCS decoder tester is mounted on four soft rubber feet. The TCS decoder tester sets up in seconds with the simple attachment of track power via screw terminals. Our tester is 100% compatible with any command station

Connections included for your decoder:

  • 8-Pin NMRA (NEM 652 Standard)
  • 21-Pin MTC (NEM 660 Standard)
  • 6-pin inline (NEM 651Standard)
  • 22-Pin Plux (NEM 658 Standard)
  • Next18 (NEM 662 Standard)
  • 21-Pin TCS (modified NEM 660 for onboard logic circuits - not current TCS production)
  • Screw Terminals (for hard-wire decoders or for use with the TCS expansion board)

Connect a DT-AUX board for even MORE connections!

4.5" x 3.5" x 1.4" or 11.4cm x 8.9mm x 3.6mm

Decoder Tester Diagram

1. Power Connections — Connect the output of your command station here.

2. Jumper Pins — Use the supplied jumper to connect the center pin and the right pin for any decoder which doesn’t use the NEM651 connecter. Jumper the left pin and the center pin for decoders with the NEM651 plug.

3. 8-Pin NMRA Plug — Pin 1 is in the lower right corner.

4. NEM651 Plug — Pin 1 is on the right.

5. Screw Terminals — Use these for hardwire decoders or attaching the Decoder Tester AUX board.

6. Next18 Connector — Pin 1 is on the upper left.

7. MTC 21 Pin Connector — Index pin is on the bottom left. See reverse side for more information.

8. PluX22 Pin Connector — Index pin is in the middle on the left.

9. TCS 21 Pin Connector — Index pin is on the bottom left. See reverse side for more information.

Add a DT-AUX for Additonal Decoder Connections

The DT-AUX board adds a JST9, MC JST, FL2 JST, and a WOW101 Auxiallary connection to your decoder tester. Plug this board directly into the screw terminals of the Decoder Tester and you will have a complete, plug in decoder test setup.

MTC 21-Pin Connectors

Decoders which use the MTC 21-Pin connector use external transistors to turn on functions 5 and 6. All current WOW121 decoders support this interface.

TCS 21-Pin Connectors

This is an outdated standard that is no longer employed on WOW121 decoders. Only use this connector for WOW121-Steam decoders purchased before May 15, 2017.


Pair with a decoder tester aux board (DT-AUX) for added convenience when connecting decoders.