It really depends on what English you’re hearing, zabi1. If it’s American English, you can be sure the usage would be “on TV,” as in “I saw you on TV last night.” If it’s British English, I imagine it would likely be “in TV,” as in “I saw you in TV last night.” This, I must admit, would further depend on what part of England or of the United Kingdom the utterance is being made. The usage of “on” or “in” varies from one linguistic area to another, and is actually more conventional and idiomatic than logical. As one language observer said, “Londoners live in a street and stay in farm cottages at weekends, but New Yorkers and English-speaking Manilans live on a street and stay in farm cottages on weekends.”