The ever increasing use of computers, microprocessors, and elaborate logic control systems constantly present designers with the problem of transmitting digital data from one system to another. Digital communications between components of systems ranging from machine controls in a factory to consumer appliances and automotive systems have made data line drivers and receivers as prevalent as power supplies.
Many systems use a central computer or controller with several remote terminals or control points. Remote stations may be a few feet or thousands of feet from the central computer. Even small independent systems will usually have one or more pieces of peripheral hardware such as a printer located at some, usually short, distance away. The need for dedicated data transmission products became more apparent as the industry matured. At first, simple single-ended data transmission was used; products were basic and often tailored for each specific system. Then widespread data transmission required system compatibility, and industry standards were adopted. Before addressing the standards and their applications, we will look at the basic line circuit requirements and general purpose data line drivers and receivers.