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Capacity of these systems increased in the middle of the century, while in the 1950s researchers began to take seriously the possibility of saving money on the terminal equipment by using
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was improved to the point that digital connections became the cheapest ones for all distances, short and long. By the end of the century, analog connections between and within
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by sending each at a different frequency. Multiple layers of multiplexing may ultimately be performed upon a given input
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is an example of frequency-division multiplexing. Many television programs are carried simultaneously on the same
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Carrier systems typically transmit multiple channels of communication simultaneously over the
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In the 1920s, frequency-division multiplexing could carry several circuits on the same
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The purpose of carrier systems is to save money by carrying more traffic on less
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spacings required by digital systems, long-distance still used
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link by frequency-division multiplexing. At a given receiving
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and similar systems carried hundreds of calls at a time on
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124:. Prominent multiplexing methods of the
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