This document discusses different types of transmission media used for physical layer communication, including twisted pair cables which use twisting of copper wires to reduce noise, unshielded and shielded twisted pair cables, coaxial cables which have a central conductor surrounded by insulating material and outer conductor, and fiber optic cables which transmit data as pulses of light through glass or plastic fibers. It provides figures and a table comparing properties of these media.

1. Transmission Media

2. Figure 7.1 Transmission medium and physical layer

3. Figure 7.2 Classes of transmission media

4. Figure 7.3 Twisted-pair cable

5. Twisted Pair
 Provide protection against cross talk(noise)
 One wire-signals
 Second wire-Ground reference
 Twisting increases probability of both the
wires are effected by noise.
 Therefore no of twists per unit length
determines the quality of cable.

6. Figure 7.4 UTP and STP cables

7. Table 7.1 Categories of unshielded twisted-pair cables

10. Figure 7.5 UTP connector

11. Coaxial cable

12. Categories of coaxial cables

15. Figure 7.10 Fiber optics: Bending of light ray