Physical Layer

The lowest layer of the Open Systems Interconnection Model is concerned with electrically or optically transmitting raw unstructured data data bits across the network from the physical layer of the sending device to the physical layer of the receiving device.

It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer, one might find "physical" resources such as network hubs, cabling, repeaters, network adapters, or modems.

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  • coordinates the functions required to carry a bit stream over a physical medium

  • deals with the mechanical and electrical specifications of the interface and transmission medium

  • defines the procedures and functions that physical devices and interfaces to perform for transmission to occur

The Physical Layer is concerned of:

  • Physical characteristics of interfaces and medium

  • Representation of bits for transmission

  • Data rate

  • Synchronization of bits

  • Line configuration

  • Physical topology

  • Transmission mode

Theoretical Basis

  • analog data

    • refers to information that is continuous

    • infinite number of values in a range

  • digital data

    • refers to information that has discrete states

    • limited number of values image::analog-and-digital-data-signal.png[]