Anna University Coimbatore 2009 B.E Electronics

be sent using OFF as less than -3 volts and ON as greater than +3 volts. The data
must be transmitted using NRZ-L encoding.
19. explain the mode for propagating light along optical channels.
There are 2 modes for propagating light along optical channels, multimode and
single mode.
Multimode: Multiple beams from a light source move through the core in various
paths.
Single mode: Fiber with extremely small diameter that limits beams to a few angles,
resulting in an almost horizontal beam.
20. What is refraction?
The phenomenon related to the bending of light when it passes from 1 medium
to a different.
21.How are the guided media differing from unguided transmission media?
Guided transmission media Unguided transmission media
1.Guided indicate, medium is contained 1.Unguided medium does not
have any within physical boundary Physical boundary
2.Transmission takes place through wire. 2.It is a wireless transmission.
22. elaborate the disadvantages of optical fiber as a transmission medium?
The disadvantages of optical fiber are
· Very expensive.
· Installation and maintenance is difficult.
· Fragility.
23. elaborate the criteria used to evaluate transmission medium?
The criteria used to evaluate transmission medium are
· Throughput
· Propagation speed
· Propagation time
· Wavelength
24. provide the relationship ranging from propagation speed and propagation time?
Propagation time = distance / propagation speed
The time needed for a signal or a bit to travel from 1 point to a different is
called Propagation time.
Propagation speed is the distance, a signal or a bit travel through a
medium in 1 second.
25.Explain cross talk and what is needed to decrease it?
Effect of 1 wire on a different is called as cross talk. 1 wire will be the sending
antenna and the other wire will be the receiving antenna. We can use the shielded
twisted pair cable or coaxial cable for transmission, which contains metal foil to
decrease cross talk.
UNIT-II
DATA LINK LAYER
1.What are the responsibilities of data link layer?
Specific responsibilities of data link layer include the subsequent.
a) Framing
b) Physical addressing
c) Flow control
d) fault control
e) Access control
2. Mention the kinds of errors.
There are two kinds of errors
a) Single-bit fault.
b) Burst-bit fault.
3. describe the subsequent terms.

Earning:   Approval pending.