This document provides an overview of the physical layer of the OSI model, detailing its role in data transmission and the types of signals (analog and digital) used. It describes common devices such as hubs, switches, repeaters, bridges, and modems that facilitate network connectivity, as well as different physical topologies and transmission media. The physical layer is crucial for defining the mechanical and electrical specifications of interfaces and the medium used for communication.

1. PHYSICAL LAYER
By: Najam Sajid
Mob: +923351970482

2. Introduction
• How to connect two or more devices?
• OSI Model
--> Open Systems Interconnect
 Set of protocols
• Introduced in first time in 1770s by ISO
(International Standards Organization)
• Composed of 7 Layers
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Physical Layer 2

3. 7.Application Layer
6.Presentation Layer
5.Session Layer
4.Transport Layer
3.Network Layer
2.Data Link Layer
1.Physical Layer
Advice
Person
Sales
Trust
Not
Do
Please
OSI Model Layers
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4. PHYSICAL LAYER
• It deals with the mechanical and electrical
specifications (Devices)
• Physical characteristics of interfaces and
medium.
• To move data in the form of electromagnetic
signals across a transmission medium
• The physical layer data consists of a stream of
bits (sequence of Os or 1s)
• Bits are encoded into signals
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5. PHYSICAL LAYER
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6. Signals
A signal is an electric current
or electromagnetic field used to convey data
from one place to another.
A Transmitter encodes a message into a
signal, which is carried to a receiver by the
communications channel.
Signals can be interpreted as either Analog or
Digital
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7. Digital Signals
• Digital signals are non-continuous, discrete
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8. Analog Signals
• Analog signals are continuous, non-discrete
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9. Devices
Some of the common devices are:
Hub
Switch
Repeater
Bridge
Modem
PC, Mobile phone, Telephone or Cables etc are
also devices use for data communication.
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10. Hub
• Centralize device that connects many
devices to share data
• Less secure
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11. Switch
• Device that connects many other devices
together to make a network
• More intelligent then Hub
• More secure
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12. Repeater
• Regenerates the signal (Electrical, Wireless or
Optical) which are corrupted due to long
distance
• Overcome the distance limitations of the
transmission media.
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13. Bridge
• Creates a single aggregate network from
multiple communication networks
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14. Modem
• The word Modem comes from Modulator-
Demodulator
• Modulation: Digital signals to analog
• Demodulation: Analog signals back to Digital
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15. Physical Topologies.
How the devices are connected to make a
network ?
Mesh topology
Star topology
Bus topology
Ring topology
Hybrid topology
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21. Transmission Medium
• Anything that can carry information from a
source to a destination.
• Uses cables or electromagnetic signals
to transmit data.
Types of Transmission Media
• 1. Wired or Guided Media or Bound Transmission
Media
• 2. Wireless or Unguided Media or Unbound
Transmission Media
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23. THANKS
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