From the upstream project:

> Can I change the display of all ESLs in a store at once ?

No. For two reasons:

Unlike radio waves, optical communication must be line-of-sight. Even from wall and ceiling reflections, an unique transmitter has no chance of reaching all of the hundreds or thousands of ESLs in a store.

Each ESL has an unique address which must be specified in update commands. There's no known way to broadcast display updates.