This diagram illustrates the Physical layer (Layer 1) of the OSI model. The Physical layer is responsible for the ultimate transmission of data over network communications media. It operates with data in the form of bits that are sent from the Physical layer of the sending (source) device and received at the Physical layer of the destination device. Ethernet cabling, Token Ring network technology and SCSI all function at the Physical layer of the OSI model. Hubs and other repeaters are standard network devices that function at the Physical layer. Cables and connectors also are a part of the Physical layer.

At the Physical layer, data are transmitted using the type of signaling supported by the physical medium:

• electric voltages
• radio frequencies
• pulses of infrared or ordinary light

Related References - OSI Model Tutorial, Ethernet, hub
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