0 1 5 ). ▁ ▁Most ▁of ▁these ▁services ▁were ▁initially ▁subscription - based . ▁Free , ▁advert ising - supported ▁streaming ▁services ▁such ▁as ▁Pl uto ▁TV ▁are ▁also ▁available . ▁These ▁services ▁generally ▁do ▁not ▁offer ▁most ▁of ▁the ▁high - profile ▁original ▁content ▁available ▁on ▁cable , ▁satellite ▁or ▁subscription ▁video ▁services ▁and ▁instead ▁package ▁r er uns ▁and ▁other ▁arch ival ▁programming ▁into ▁online - ex clus ive ▁channels . ▁ ▁The ▁business ▁of ▁television ▁ ▁Over - the - air ▁( OT A ) ▁commercial ▁stations ▁and ▁networks ▁generate ▁the ▁vast ▁majority ▁of ▁their ▁re venue ▁from ▁advert is ements . ▁According ▁to ▁a ▁ 2 0 0 1 ▁survey , ▁broadcast ▁stations ▁allocated ▁ 1 6 ▁to ▁ 2 1 ▁minutes ▁of ▁programming ▁time ▁per ▁hour ▁to ▁commer ci als . ▁Most ▁cable ▁networks ▁also ▁generate ▁income ▁from ▁advert is ements , ▁although ▁most ▁basic ▁cable ▁networks ▁also ▁receive ▁subscription ▁fe es , ▁which ▁are ▁the ▁other ▁main ▁source ▁of ▁re venue ▁for ▁the ▁cable ▁operators . ▁However , ▁prem ium ▁cable ▁networks ▁( such ▁as ▁H BO ) ▁do ▁not ▁air ▁commer ci als ; ▁instead , ▁cable ▁television ▁subscri bers ▁must ▁pay ▁an ▁extra ▁fee ▁to ▁receive ▁this ▁type ▁of ▁pay ▁television ▁service . ▁ ▁Network s ▁tradition ally ▁allocate ▁a ▁portion ▁of ▁commercial ▁time ▁during ▁their ▁programs ▁( us ually ▁total ing ▁between ▁five ▁and ▁ 6 ½ ▁minutes ▁per ▁hour , ▁depending ▁on ▁the ▁length ▁of ▁the ▁program ▁being ▁a ired , ▁sometimes