This kind of large-area lamps that need centralized control generally have a main switch and a group switch, just turn it on.

Some have independent switches, which are simple and practical.

A library is an institution that collects, sorts out and collects books and materials for people to read and refer to. As early as 3000 BC, libraries appeared. Library has the functions of preserving human cultural heritage, developing information resources and participating in social education. Library is the external storage and selective transmission mechanism of social memory (usually expressed in written records).