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THOUGHTS ABOUT THE RS-232 STANDARDThe RS-232 standard defines a relatively low performance interconnection between two computing devices. The standard is intended to meet the needs of the user with low cost and relatively simple technical constraints. "It's cheap and easy" -- that's RS-232 connectivity. As you'll find when you attempt to actually connect two devices using the RS-232 method, it's not always as easy as it was intended. RS-232 is, however, a relatively easy interface to engineer and implement. In general terms, the standard serves as a reference for the design of input/output connectivity for equipment. A good example of how the "reference" nature of the standard is often misunderstood is in the description of the type of connector to be used. It was common for many years to use a female 25 pin connector for a modem and a male 25 pin connector for a computer. This became so common that it was viewed as part of the standard. In fact, the RS-232 standards do not require any particular type of connector. Moreover, the number of wires used to connect two machines can vary depending on how the interface is implemented. It is this variability that sometimes makes RS-232 seem more confusing that it really is. The Electronics Industry Association (EIA) is an industry group based in Washington, D.C., which recommends and publicizes standards related to electronic components and communications. EIA recommended standard number 232, officially called the "Interface between Data Terminal Equipment and Data Communications Equipment Employing Serial Binary Data Interchange", specifies RS-232. For many years, the third revision was the current issuance of the standard: the RS-232C standard ("RS" means "recommended standard" and "C" is for the third revision of the standard. |
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