7 - Data Communications

Abstract

This chapter discusses the evolution of the field of data communications. The chapter reviews how computers communicate with one another, and discusses the various arrangements of communication networks and their advantages and disadvantages. Data communications is the transmission of computer data between computer systems and terminals. Computers transmit bits of digital data. Telephone lines transmit analog data—continuous waveforms. A modem—modulator/demodulator—is used to convert digital data into analog data for transmission over phone lines. Transmitted data travels over the telephone network to the main computer, where another modem converts the analog data back to digital data. Modems with acoustic couplers are used when terminals are connected to the standard dial-up telephone network. Data may be carried on many different media, such as, twisted-pair wire, cable containing many twisted-pair wires, coaxial cable, microwave transmission, satellite transmission, and fiber optic glass cable. Microwave transmission does not use cables or wires. Signals are transmitted through the air between microwave stations.