Crossover cable is a cable that is used to connect for communication between two or more devices by crossing over (by reversing) their individual pin contacts. Two basic connections either an RS-232C or a telephone jack connection are possible. Null modem term is often used to call this crossover cable because of the possible reasons to connect two computers directly to each other.
Same type of devices are connected with the help of crossover cable, for example DTE-DTE (Data terminal equipment) or DCE-DCE (Data Communication Equipment). In simple words a computer to computer or switch to switch etc. are usually connected asymmetrically (DTE-DCE), and by a modifying internal cable pairs, a cable called a crosslink. Such distinction of devices was introduced first by International Business Machines (IBM). Most common example of crossover cable is CAT-5 where maximum transmission length is 328ft or 100m and can support data rate of hundreds of Mbps. The crossing wires in crossover cable or in a connector adaptor allows:
- connecting two or more devices directly, output of one to input of the other or vice versa.
- Connecting two terminals (i.e. DTE) devices communicate without an interconnecting hub, i.e. Hub or PCs.
- Linking two or more networking devices i.e. hubs, switches or routers (DCE) together, possibly to work as one networking connection.
- Playing a game competitively (one person at each computer) with fast response time
- To test one computer by troubleshooting the behavior at the other computer and then implement the solution.
- Cost can be significantly reduced by using single hub for connecting two or more devices.
While connecting crossover cable if auto MDI or MDI-X feature support is available on the switch, hub, network card or other network devices then crossover cable is not necessary to use because crossover function would be automatically enabled when it is required.