Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
There is no rule concerning the TV itself as an object. However, there are rules for what is presented in it. If what is presented is useful and preaches the good and encourages it and warns about the bad and forbids it, it is then lawful to own a TV for this purpose only. This is found in such programs like the religious ones. But if what is presented is from what Allah has forbidden for us like music, dancing and the dirty programs which can lead to tumult and disintegration because of the series, films and the like, these should undoubtedly be avoided completely. The Television is a source for both matters. So, if the person is certain that he could control and supervise what his wife and children watch, making sure that it is all lawful, so there is no harm in having one. But if he is in doubt, he should leave it out, as it could gradually bring the Satan and its bad tricks to his home. Allah Says (Interpretation of meaning): {O you who believe! Follow not Satan's footsteps. If any will follow the footsteps of Satan, he will (but command what is indecent and wrong}.[24:21] And Allah knows best.