Light boxes?

What's the proper name for old destination displays? Is it that, or destination describer or light box or what?   

I know there is the thread about the "old describers" at Baker Street. But in several YT videos I've heard those hanging above platforms being referred to as "light boxes"   i.e. those that had a bulb behind each destinaton. I'm asking as I want to find out more about some of the "odd texts/destinations" that existed on  these "light boxes" at Earls Court, Gloucester Road, South Ken and HSK on the District and Circle Lines. So if I have the right term it will be easier to search on the net.