|  |  | Overview
The function of the physical layer is to transmit data by defining the electrical specifications between the source and destination. Once it reaches a building, electricity is carried to workstations, servers, and network devices via wires concealed in walls, floors, and ceilings. Data, which can consist of such things as text, pictures, audio, or video, travels through the wires and is represented by the presence of either electrical pulses on copper conducting wires or light pulses in optical fibers. In this chapter, you will learn about the basic theory of electricity. This will provide a foundation upon which networking at the physical layer of the OSI model can be understood. You will also lean how data is transmitted through physical media, such as cables and connectors. Lastly , you will learn about the different factors that affect data transmission such as, alternating current (AC) power line noise.