3. 7.3
So a recap
• The physical layer is responsible for
movement of individual bits from one hop
(node) to the next. It deals with the mechanical
and electrical specifications of the interface and
transmission medium, as well as the procedures
and functions they have to perform for
transmission to occur.
• PR DSL PT
5. 7.5
• The physical layer (Layer 1) specifications, which are also
typically standards from other organizations that are referred to
by OSI, deal with the physical characteristics of the
transmission medium. Connectors, pins, use of pins, electrical
currents, encoding, and modulation (depending upon the
media) are all part of different physical layer specifications.
• Multiple specifications are sometimes used to complete all
details of the physical layer. For example, RJ-45 defines the
shape of the connector and the number of wires or pins in the
cable. 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 connector
for an Ethernet connection, Ethernet, RJ-45 and CAT 5 cable
physical layer specifications are used.
• Example Standards: EIA/TIA-232, V.24, EIA/TIA-449,
V.35, RJ45, Ethernet (802.3), Token Ring (802.5), Wireless
LAN (802.11), Wireless MAN or BWA (802.16) etc.
8. 7.8
GUIDED MEDIAGUIDED MEDIA
Guided media, are those that provide a conduit fromGuided media, are those that provide a conduit from
one 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.
9. 7.9
Twisted-pair cable
One can simplistically say, that by twisting, unwanted signals
are mostly canceled out, when relative measurement is made.
15. 7.15
Unshielded twisted pair cable with different twist rates
ScTP, also known as FTP
Shielded twisted pair cable with different twist rates
S/STP, also known as S/FTP
Single-core cable, 25-pair, 50 conductors
18. 7.18
Categories of coaxial cables
The origin of the RG designations is in old, long-obsolete military specs; RG stands
for Radio Guide (Radio Govt as per Forouzan)
1.63/10.5 mm
0.9/5.0 mm
0.81/6.1 mm
Core/Dia
33. 7.33
UNGUIDED MEDIA: WIRELESSUNGUIDED MEDIA: WIRELESS
Unguided media transport electromagnetic wavesUnguided media transport electromagnetic waves
without using a physical conductor. This type ofwithout using a physical conductor. This type of
communication is often referred to as wirelesscommunication is often referred to as wireless
communication.communication.
