This is a rare sighting. These light up panels, installed in the Paris métro stations back in the 1930s were known as PILIs, or plans indicateurs lumineux d’itinéraires. Users would push two buttons, one indicating the starting point of their journey, and a second one indicating their ultimate destination. A pathway would light up, showing the trip. If a change was involved, the lightpaths would be in different colors.
Now a relic, there are a few of these vintage displays present in a handful of métro stations (this one is at Ecole Militaire in the 7th arrondissement) but they are no longer functional. I guess they were hard to maintain, and, as such, fell into disrepair.
Still, I'm glad that they can be spotted from time to time, even if it they are merely decorative.