A frequency in a communications channel modulated to carry analog or digital signal information. For example, an FM radio transmitter modulates the frequency of a carrier signal and the receiver processes the carrier signal to extract the analog information. An AM radio transmitter modulates the amplitude of a carrier signal.
A communications system providing a number of point-to-point channels through some type of multiplexing . T-1 and T-3 carrier services are examples of carrier systems that can be used between points in a Wide Area Network (WAN) .