Other Interface Standards

o    In unbalanced mode, EIA 449 calls for the use of only the first pin of each pair of category 1 pins and all category 2 pins •     RS 422 Balanced Mode o    Balanced circuit specification o    Defines two lines for the propagation of each signal o    Signal again uses a common return

o    EIA utilizes all pairs of pins in category 1 but does not use the category 2 pins o    The ration of data rate to distance is much higher in this case than EIA 232 o    In balanced mode two lines carry same signal which are not identical to each other o    Signal on one line is the complement of the other Canceling of Noise in the Balanced Mode When plotted, complement of the signal looks like the mirror image of the signal o    EIA 449 provides much better functionality than EIA 232 o    However it requires a DB 37 connector that industry has been reluctant to use because of the widespread use of DB 25 o    To encourage acceptance of EIA 449, EIA developed a version of EIA- 449 that uses DB 25 pins o    Pin    functions    of    EIA    530    are    essentially    those    of    EIA    449 CATEGORY 1 pins plus three pins from category 2 o    EIA 530 does not support a secondary circuit