Appendix B - Cabling, Hardware, & Electrical
User Guide
301
transmission speeds range between 9,600 bps and 19,200bps (used in most automation and
console applications) to 115,200 bps (used by the fastest modems).
Cable Length
The original RS-232 specifications were defined to work at a maximum speed of 19,200 bps
over distances up to 15 meters (or about 50 feet). That was 30 years ago. Today, RS-232 inter-
faces can drive signals faster and through longer cables.
As a general rule, consider:
•
If the speed is lower than 38.4 kbps, you are safe with any cable up to 30 meters (100
feet)
•
If the speed is 38.4 kbps or higher, cables should be shorter than 10 meters (30 feet)
•
If your application is outside the above limits (high speed, long distances), you will need
better quality (low impedance, low-capacitance) cables.
Successful RS-232 data transmission depends on many variables that are specific to each envi-
ronment. The general rules above are empirical and have a lot of safety margins built-in.
