Editing RS-232 (section)

===Cables===
{{main|Serial cable}}

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 {{convert|15|m|abbr=on|-1}} 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 {{convert|300|m|abbr=on|-2}}.<ref>{{cite web |url=http://aplawrence.com/Unixart/serial.art.html |title=Serial Wiring |date=1992 |work=A. P. Lawrence |author-last=Lawrence |author-first=Tony |access-date=2011-07-28}}</ref> For longer distances, other signal standards, such as [[RS-422]], are better suited for higher speeds.

Since the standard definitions are not always correctly applied, it is often necessary to consult documentation, test connections with a [[breakout box]], or use trial and error to find a cable that works when interconnecting two devices. Connecting a fully standard-compliant DCE device and DTE device would use a cable that connects identical pin numbers in each connector (a so-called "straight cable"). "[[Gender changer]]s" are available to solve gender mismatches between cables and connectors. Connecting devices with different types of connectors requires a cable that connects the corresponding pins according to the table below. Cables with 9 pins on one end and 25 on the other are common. Manufacturers of equipment with [[8P8C]] connectors usually provide a cable with either a DB-25 or DE-9 connector (or sometimes interchangeable connectors so they can work with multiple devices). Poor-quality cables can cause false signals by [[crosstalk]] between data and control lines (such as [[#RI|Ring Indicator]]).

If a given cable will not allow a data connection, especially if a [[gender changer]] is in use, a [[null modem]] cable may be necessary. Gender changers and null modem cables are not mentioned in the standard, so there is no officially sanctioned design for them.