A screen cap would help. Most movie pagers from that era would either be the real deal or have a connector wire running to a controller for functions to camera. It would be the same basis as Sci fi hand held props that need to function in real time with a graphic or text before practical technology caught up. The last time I recall working with prop pagers was, I believe, School for Scoundrels, over 15 years ago now. Those used the same old off camera controller for on camera functions.