# OSI Layer 1: The Physical Layer The first layer of the stack deals with raw electrical signals. Protocols on this layer define things like voltage levels, cable specifications, connectors, layout of pins and communication frequencies (in the case of wireless communications). Ethernet, USB, Bluetooth and CAN are examples of protocols running on this layer. ^5l05il ![[OSI Model - Wikipedia#^ajrpl3]] It can be said that [[Hub|hubs]] and repeaters operate on the physical layer. ![[Hub#^nl1msc]]