Yes, it is possible to use the P/N 010-4004-0002 DSX modules which were designed to operate in a =24Vdc environment in one of Telect's -48Vdc chassis, if you replace all of the LEDs in the module with a -48Vdc LED.  The only difference between the 010-4004-0002 (+24Vdc) and the 010-4004-0000 (-48Vdc) module is the operating voltage of the LED.  So, if you were to switch out all of the LED's in the module, you could operate the module in a chassis that is powered by -48Vdc.    

If you do not replace all of the LEDs in the module, it will not operate correctly.