It defines the signals and voltages used when data is exchanged between a computer or terminal and a modem or serial printer. The entire standard covers many more functions than are used in most data communications applications. If you're using an Apple computer, ask your dealer for the correct modem cable for your Apple model. The minimum required for the modem to operate is as follows. Make sure the RS-232 cable is shielded.
Cables are normally six feet long, but longer lengths are possible.
If you encounter problems with signal degradation, try a shorter cable. If you decide to build your own cable, use a low-capacitance cable. This document was received from the US Robotics On-Line Support , document number 548.