What do DCT 1, DCT 2, and other abbreviations in networks mean?

[Godwin Kessy]

Guys what do these simply mean DCT 1, DCT 2 and others.. As used in networks.. I just what a brief explanation.. to basically differentiate them. I have followed up, it's abbreviation for Discrete cosine transform.

 

[Godwin Kessy]

Any replies guys.. I actually found this in some programs that required me to select phone type like Nokia 9500 and others, in the list the DCT2, DCT3, DCT4 were included, my phone type is not in the list that is why i have to at least understand what do they mean so that i can select one of them if required... Thank you!