A patch cable, sometimes called a patch cord, is an optical or electrical cable with a connector on each end, used to connect two devices such as network components, or audio or video devices. Patch cables are widely available commercially, and are generally not costly, but many users make their own, especially when they need to put together a special configuration, such as connecting two devices without a common connection type.
Most patch cables are generally short — usually no more than 6 feet (about 2 m), more or less, and in many cases as short as 3 inches (about 8 cm). They can be made in any length needed, however, and it's not unusual to have a patch cord of hundreds of feet “snaked” behind the walls in an office. In general, the longer the patch cable, the thicker it must be to accommodate the extra shielding and insulation necessary to prevent loss of signal and interference from extraneous radio and electromagnetic interference. The length of a patch cable is usually determined by the distance between the two devices to be connected, and the desire of users to minimize the clutter of loose cable. Shorter patch cables are sometimes called “pigtails.” Patch cables usually are made of stranded wires, often in “twisted pairs,” to make the cable itself more flexible, although some are available in solid copper.
Some devices, like computer mouses, continue to rely on built-in cabling for their connections. The trend, however, is to construct devices with ports for different connection types, and either provide patch cables or let the end user provide them. Due the vast number of different patch cables available, they're made in a wide variety of colors to help distinguish one type from another. Bright blue patch cables, for example, are usually equipped with category 5 (Cat-5), which describes both the connector and the type of cable used — connectors on both ends and are used to link network devices together.
Another common type of patch cable is coaxial cable, which is generally black and connects many different devices, often to transmit radio or audio-video (AV) signal. A microphone cable is a black patch cable equipped with XLR connectors, multiple-pin connectors that connect male-to-female and snap into place, and home stereo users are familiar with the RCA jack, which is installed on the multicolored patch cables supplied with many home stereo components.
Users are sometimes frustrated when they try to re-use a patch cable that's been in place and working perfectly for years, but must be removed for some reason. Upon re-installation, the signal does not transmit properly and device operation is compromised. In these cases, the cables adapt to the particular set of bends and twists of their initial installation, and when removed and installed on the same or another set of devices, they may lose their connections entirely or develop other problems. For this reason, prudent users always have spare patch cables available.