In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to transmit on, the line code to use and similar low-level parameters, are specified by the physical layer.
RTL8201 Ethernet PHY chip
Micrel KS8721CL – 3.3 V single power supply 10/100BASE-TX/FX MII physical layer transceiver
A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.
Network Packet
Fiber-optic cables are used to transmit light from one computer/network node to another.
Computers are very often connected to networks using wireless links.
An ATM network interface in the form of an accessory card. A lot of network interfaces are built-in.