如果只有40米, EIA-485能做到2Mbps
本帖最后由 mxh0506 于 2011-8-29 21:08 编辑
EIA-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers data transmissionspeeds of 35 Mbit/s up to 10 m and 100 kbit/s at 1200 m. Since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4,000 feet (1,200 m)). A rule of thumb is that the speed in bit/s multiplied by the length in meters should not exceed 10E+8. Thus a 50 meter cable should not signal faster than 2 Mbit/s.
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