High Quality Content by WIKIPEDIA articles! In North American cable TV networks, the radio frequencies used to carry signals to the customer are allocated to standardarized channel numbers listed in the CEA standard 542. Cable channel frequencies are generally different from off-air broadcast frequencies. Since the cable network is a closed system, frequencies used for over-the-air services such as mobile radio, cellular telephone, or aircraft communications can be assigned to carry television programming. The assignment of channel frequencies must on the one hand reduce the effects of distortion and mutual intereference generated within the cable television distribution system, and on the other hand maintain compatibility with the customer`s connected equipment.