A user is authenticated to operate an electrical device in a network, by encoding an identification symbol with identification data that identifies the user, and by encoding a composite symbol with the identification data and with operating data that enables the electrical device to be operated. The composite symbol is associated with the electrical device to be operated. An image of the identification symbol, and an image of the composite symbol, are captured and compared. The user is enabled to operate the electrical device when the identification data in the composite symbol matches the identification data in the identification symbol.