The first layer (physical Layer) and its function is to connect the device to the transmission media Whatever the type of Conveyor medium, whether it is Optical fiber, UTP, Coaxial cable, or even the conveyor medium is vacuum. Function (Physical Layer) converts the information to be transmitted (Transmitted Data) into electrical, optical or wireless signals suitable for the conveyor medium and the signal form (Digital Encoding) suitable for the conveyor medium type and vice versa.