Telect's traditional DSX-1 panels support a single operating voltage of either -48Vdc or +24Vdc for powering the LEDs on the front of the panel. So, your panel selection is dependent on the operating voltage you will be applying. Panels supporting +24Vdc will be specifically labeled as operating at +24V. For example the 010-0156-0635 and 010-0156-0657 panels both use a +24V operating voltage for the LEDs. If the operating voltage is not specified in the part description it supports -48Vdc for powering the LEDs on the panel.