You need to give examination called LEET. This is a national level examination and students can also take in state level government colleges. This examination is for lateral entry students for direct admission in 2nd year b. Tech after diploma. 

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You’ll need to qualify through JEE Main and JEE advanced and you can get admission for first year of four year degree course. [ Many state or private colleges will admin diploma holder in the second year directly but not the IITs or NITs. ]