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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
The name “physical layer” can be a bit problematic. Because of that name, and because of what I just said about the physical layer actually transmitting data, many people who study networking get the impression that the physical layer is only about actual network hardware. Some people may say the physical layer is “the network interface cards and cables”. This is not actually the case, however. The physical layer defines a number of network functions, not just hardware cables and cards.
A related notion is that “all network hardware belongs to the physical layer”. Again, this isn't strictly accurate. All hardware must have some relation to the physical layer in order to send data over the network, but hardware devices generally implement multiple layers of the OSI model, including the physical layer but also others. For example, an Ethernet network interface card performs functions at both the physical layer and the data link layer.
The following are the main responsibilities of the physical layer in the OSI Reference Model:
Definition of Hardware Specifications: The details of operation of cables, connectors, wireless radio transceivers, network interface cards and other hardware devices are generally a function of the physical layer (although also partially the data link layer; see below).
Encoding and Signaling: The physical layer is responsible for various encoding and signaling functions that transform the data from bits that reside within a computer or other device into signals that can be sent over the network.
Data Transmission and Reception: After encoding the data appropriately, the physical layer actually transmits the data, and of course, receives it. Note that this applies equally to wired and wireless networks, even if there is no tangible cable in a wireless network!
Topology and Physical Network Design: The physical layer is also considered the domain of many hardware-related network design issues, such as LAN and WAN topology.
Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.
Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).
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In Data Link Layer is MAC address located.
Medium Access Control (MAC) defines who can use the network when multiple computers are trying to access it simultaneously
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Network layer is responsible for the routing of data (packets) through the network. It handles the addressing and delivery of data.
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RS-232 is also in physical layer, like as X.21, EIA 232, and G730.
This is OSI Layers for TCP/IP protocol its for network, but we know that network is not only thing on ours comps, there is OS operating system, behind OS is memory, CPU, GPU,...
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yes thanks ,finally I concluded that
,in that layer there is only one layer exist as hardware (may be 2 wire ) which is physical layer
in physical layer has a lot of pulse signals .having certain duration (like TDMA) for giving data for each layer
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