Solution:

1. MODEM or CODEC have been tossed to emphasize this fact. What is meaning of this line?

Answer: In order to overcome the issue the concept of MODEM or CODEC applied or used.

2. what is CRT?

Answer: Cathode Ray Tube (CRT). Previous TV standard.

3. what is the meaning of luminosity?

Answer: Luminocity means the presence of white light.