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SERIAL DATA TRANSMISSION The simplest, most economical, and easiest to use method of transferring digital information from one point to another is serial data transmission. In a serial system, the digital data is sent one bit at a time. This means only one pair of transmission wires is required. The serial transmission of data is far slower than parallel transmission. In most computer systems, the low speed is not a disadvantage. Data rates achievable in serial data systems are sufficiently high to make them very practical. Serial data transmission is preferred because it is inexpensive. It is especially beneficial in transferring data over long distances. For long distances, you can see that multiple parallel lines are far more expensive than a single cable. Low-speed serial data transmission also offers another benefit. The data rate is slow enough to permit the transmission of data over telephone lines. In this case the digital data is converted into a pair of audio tones representing binary 1s and 0s. These can be transmitted economically for long distances over standard telephone lines. In addition, low cost tape recorders can be used to record the serial data. This provides a low cost means of mass data storage and retrieval. Standard audio cassette recorders are widely used in this application. Serial data transmission also permits transmission of data by radio. A radio communications path represents only a single interconnecting link similar to a transmission line pair. Therefore, for data to be transmitted by radio, it must be in serial format. Serial digital data is used to modulate a radio carrier in various ways. In digital computer systems, you will find that both serial and parallel data transmission methods are used. Where high speeds and short distances are required, the parallel method is used. The serial method is used where low cost, simplicity, low speed, and long distances are necessary