7.3So a recap• The physical layer is responsible formovement of individual bits from one hop(node) to the next. It deals with the mechanicaland electrical specifications of the interface andtransmission medium, as well as the proceduresand functions they have to perform fortransmission to occur.• PR DSL PT
7.5• The physical layer (Layer 1) specifications, which are alsotypically standards from other organizations that are referred toby OSI, deal with the physical characteristics of thetransmission medium. Connectors, pins, use of pins, electricalcurrents, encoding, and modulation (depending upon themedia) are all part of different physical layer specifications.• Multiple specifications are sometimes used to complete alldetails of the physical layer. For example, RJ-45 defines theshape of the connector and the number of wires or pins in thecable. Ethernet (802.3) define the use of wires or pins 1, 2, 3,and 6. So, to use a Category 5 cable with an RJ-45 connectorfor an Ethernet connection, Ethernet, RJ-45 and CAT 5 cablephysical layer specifications are used.• Example Standards: EIA/TIA-232, V.24, EIA/TIA-449,V.35, RJ45, Ethernet (802.3), Token Ring (802.5), WirelessLAN (802.11), Wireless MAN or BWA (802.16) etc.
7.8GUIDED MEDIAGUIDED MEDIAGuided media, are those that provide a conduit fromGuided media, are those that provide a conduit fromone device to another, include twisted-pair cable,one device to another, include twisted-pair cable,coaxial cable, and fiber-optic cable.coaxial cable, and fiber-optic cable.
7.9Twisted-pair cableOne can simplistically say, that by twisting, unwanted signalsare mostly canceled out, when relative measurement is made.
7.15Unshielded twisted pair cable with different twist ratesScTP, also known as FTPShielded twisted pair cable with different twist ratesS/STP, also known as S/FTPSingle-core cable, 25-pair, 50 conductors
7.18Categories of coaxial cablesThe origin of the RG designations is in old, long-obsolete military specs; RG standsfor Radio Guide (Radio Govt as per Forouzan)1.63/10.5 mm0.9/5.0 mm0.81/6.1 mmCore/Dia
Transmission of Light through FiberAttenuation of light through fiber in the infraredregion.
Fiber Optic NetworkA fiber optic ring with active repeaters.
7.33UNGUIDED MEDIA: WIRELESSUNGUIDED MEDIA: WIRELESSUnguided media transport electromagnetic wavesUnguided media transport electromagnetic waveswithout using a physical conductor. This type ofwithout using a physical conductor. This type ofcommunication is often referred to as wirelesscommunication is often referred to as wirelesscommunication.communication.
The Electromagnetic SpectrumThe electromagnetic spectrum and its uses forcommunication.