MAX3221E: About Transmission distance

Wikipedia says:

The standard does not define a maximum cable length, but instead defines the maximum capacitance that a compliant drive circuit must tolerate. A widely used rule of thumb indicates that cables more than 15 m (50 ft) long will have too much capacitance, unless special cables are used. By using low-capacitance cables, communication can be maintained over larger distances up to about 300 m (1,000 ft). For longer distances, other signal standards, such as RS-422, are better suited for higher speeds

Hide,

Clemens' answer basically sums up your question. 

RS232 is generally specified to have a max cable length of 15m, although this is not standardized. Technically speaking, you could possibly transmit across further distances depending on data rate and voltage level. 

Hide said:

And, could you please let us know “Transmission distance vs Data rate graph” if you have any information?

I am fairly certain you can look up a graph like this online, but this shows the data rate vs cable length for several communication protocols. You will notice that RS-232 stops abruptly at 15m. 

Please let me know if this helps answer your questions.

Regards,

Tyler