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Carrier Signal <ul><li>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. </li></ul>
Carrier System <ul><li>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) . </li></ul>
carrier service provider : <ul><li>A company offering telephone and data communications between points in a state or in one or more countries. The Regional Bell Operating Companies (RBOCs) are example of carriers. </li></ul>
Modulation <ul><li>Technique for impressing information (voice, music, picture, or data) on a radio-frequency carrier wave by varying one or more characteristics of the wave in accordance with the intelligence signal </li></ul>
Amplitude Modulation (AM) <ul><li>Auditory or visual information is impressed on a carrier wave by varying the amplitude of the carrier to match the fluctuations in the audio or video signal being transmitted </li></ul>
Frequency Modulation (FM) <ul><li>The amplitude of the carrier is kept constant, but its frequency is altered in accordance with variations in the audio signal being sent. </li></ul>
Phase Modulation <ul><li>The phase of a carrier wave is varied in response to the vibrations of the sound source in phase modulation (PM). </li></ul>
Pulse-coded modulation (PCM), <ul><li>In the intelligence signal converts the carrier into a series of constant-amplitude pulses spaced in such a manner that the desired intelligence is contained in coded form. </li></ul>
Pulse-duration modulation (PDM), <ul><li>Another kind of pulse modulation is in which intelligence is represented by the length and order of regularly recurring pulses. </li></ul>
What is a wavelength? <ul><li>The distance between the peak of one wave to the next. </li></ul>
Adding intelligence to the waveform <ul><li>By modulating a waveform we can add intelligence to the transmitted wave. </li></ul>
Carrier <ul><li>The Carrier is the portion of the wave which carries no inteligence </li></ul><ul><li>the unmodulated single-frequency electromagnetic wave that carries the desired information </li></ul>