The image above shows the “M-10000 Coach Car B” for the N scale Con-Cor M-10000, which is the 1st car behind the loco.  If you look closely, you can see the holes in the underbody, above which a speaker can be mounted for a sound decoder installation. 

The recommended Digitrax sound decoder would be our SFX0416, but to use this decoder, one or more of the seat sections as shown below will need to be removed.  There is a pocket that is designed for a speaker above the underbelly and under the center section of seats.  The speaker that comes with the SFX0416 would need to be replaced with a speaker of the appropriate size. 

Step 1: Carefully remove the body from the frame per these Con-Cor’s Instructions:

“Please note in the exploded view the gray arrows pointing to the “clips” on the chassis. It is important that you use a small wooden tooth pick or similar type prying device to remove the body shell. Simply place the wooden pick between the chassis and the plastic shell and gently pry the body shell up in all locations.”

“CAREFUL: There is a chance that the chassis will fall from the body shell suddenly. Be sure you are supporting the chassis when removing the body shell.”

Step 2: As shown above, carefully remove the light board from its holders. The light board is held in place with two brass “pins” (See the arrows numbered 1 on this image).  Then lay the light board upside down, locate the 8-pin dummy plug and gently pry it out of the socket with a flathead screwdriver.

Once the dummy plug is removed, carefully insert the DN143IP, making sure to orient pin 1 to the pin 1 hole.  The bulk of the decoder should be towards the front of the car as shown in the last image.

The above image shows the car with the body and the light board removed from the brass pins as well as the dummy 8-pin plug removed.  It also shows the proper orientation for the DN143IP.  The front to the car is to the right.  You do not need to remove the two black truck pick-up wires on the rear corner of the light board. 

They’ve been engineered to have enough play to remove the board to remove the dummy plug and insert the DN143IP.  Be sure to align pin 1 in the pin 1 hole! Pin 1 is marked on the light board and is the pin with the square base on the decoder. (See the arrows numbered 2 on this image)

The last image shows the DN143IP fully installed, with the light board snapped back onto the brass pins, ready for the body to be replaced.

More on the M10000 here:

History of the Union Pacific M-10000

The Union Pacific actually won the race to have a "modern streamlined high speed train" in service first and had their M-10000 streamliner in service in early 1934 months before the Burlington's Pioneer Zephyr.

But the Burlington won the public relations battle and got more publicity for the Pioneer Zephyr which is probably remembered better than the M-10000.

The M-10000 also toured much of the USA and the interior was shown to over 1 million people, and each and every one of those million plus people got a fancy souvenir Aluminum coin made of the same material as the M-10000 body.

The Original M-10000 was scrapped in early 1942. It is a bit vague why it was scrapped so early, as other versions such as the M-10001 and M-10002 continued in service. The offical reason given was that the Aluminum in the body was needed for the "war effort". But at least one National Museum had expressed interest in preserving the train for Historical purposes.