Physical layer

 Physical layer is the first or the bottom most layer of the OSI model. This layer is used To establish or terminate a connection to a communication medium. It also defines the electrical and mechanical specifications like cables, connectors and signaling options of the medium.

Physical layer receives data from the upper layer called the data link layer. it converts the received data info bit stream. The data is then transmitted through the medium to the receiver. At the receiving end, Physical layer receives the data in bit format. It Forwards the data to the data link layer


  • Characteristics of media :- Defines the characteristics of the interface which is used for connecting the devices. It also defines the type of the transmission media such as copper wires of fiber optic cables.
  • Encoding : Defines the encoding type. Encoding means changing bit stream into signal. Before transmission, Physical layer encodes the signal into electrical or optical from depending upon the media.
  • Transmission rate :- Defines the transmission rate of bit. This provides number of bits transmitted per second. It defines how long will the duration of a bit be.
  • Transmission mode :- defines the transmission mode between two devices. Transmission mode specifies the direction of signal flowThe different types of transmission modes are –
  1. Simplex :- Communication is done only in one direction. one device can only send and the other can only receive.
  2. Half duplex :- Communication is done in both the direction but not at the same time.
  3. Full duplex :- Communication is done simultaneously in both the directions at the same time.