The document describes a simplified model for communications consisting of a source that generates data to transmit, a transmitter that transforms the information into signals, a transmission system that transports the information, a receiver that transforms the received signal back into information, and a destination that receives the data from the receiver. It then provides examples of how this model applies to data communications over a computer network using different technologies like circuit switching, packet switching, frame relay, and asynchronous transfer mode (ATM).
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