Physical Layer of OSI model - MetaTutorials

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Here, we will learn about the physical layer of the OSI reference model in detail with its diagram and functions. In this article, we will also discuss the components or devices used in the physical layer.

## What is the Physical Layer of OSI Model?

The Physical Layer of the OSI model is the bottom-most layer that activates, maintains, and deactivates the physical connection between the networking devices.
This layer is responsible for transmitting individual data bits from one networking node to another networking node. The transmission media in this layer used for data transmission can be either wired or wireless.
Hub, repeater, Multiplexer, transmitter, and modem are the devices of the physical layer.

## Functions of Physical Layer

The physical layer of the OSI model consists of various functions which play important roles in data transmission. Following are the various functions of physical layer:

1. Representation of Bits: This layer encodes the sequence of 0's and 1's bits into signals before the data transmission from one device to another.

2. Bit Synchronization: This function relates to the synchronization of all bits which are delivered between sender and receiver at a bit level.

3. Line Configuration: This function specifies the medium which shows how two devices are connected with each other in a network. It specifies the Point-to-Point and multipoint configuration.

4. Data Rate: This function of the physical layer defines the number of bits transferred each second. In simple words, we can say that it specifies the timing of transferred bits.

5. Interface: The physical layer also defines the transmission interface between the two or more connecting network devices.

6. Topologies: This layer uses the physical topologies which determine how the multiple devices are connected to each other. This function shows the physical structure of the network.
Following are the four different types of topology in the physical layer:
1. Mesh Topology
2. Star Topology
3. Bus Topology
4. Ring Topology

7. Transmission Modes: This layer of OSI model also specifies the simplex, half-duplex, and full-duplex transmission modes which show the flow of information and data in the network.

## Components of Physical Layer

The physical layer of OSI model consists of the following various components:
1. Hub
2. Repeater
3. Modem
4. Multiplexer
6. Cables and Connectors
7. Network Interface Card (NIC)

### Hub

Hub is used in the physical layer for connecting the segments of the LAN network. This device has more than one input/output port.

### Repeater

A Repeater is another hardware device which is basically used for regenerating digital and analog signals.

### Modem

Modem means Modulator or Demodulator which converts digital signals into analog signals over the telephone line.

### Multiplexer

This hardware device is used in the physical layer for combining the multiple communication signals together.