PC Hardware

Identifying Cables and Connectors

Because printers and modems can both use 9-pin and 25-pin connectors and cables, a computer technician must be able to identify the function of the cables by their connectors. Other devices, such as monitors and game ports, use 15-pin connectors. Cable identification can be confusing, but it is important. The following table summarizes how to identify common cables and connectors.

Function Computer Connector Cable Connector
Communication (serial) 9-pin or 25-pin male 9-pin or 25-pin female
Printer (parallel) 25-pin female 25-pin male
Monitor (VGA and SVGA) 15-pin female (three rows of pins) 15-pin male (three rows of pins)
Monitor (MGA and CGA) 9-pin female 9-pin male
Game port (joystick) 15-pin female (two rows of pins) 15-pin male (two rows of pins)
Keyboard 5-pin DIN female or 6-pin DIN female (PS/2) 5-pin DIN male or 6-pin DIN male (PS/2)

Troubleshooting Cables

Cables and connectors are a very common source of problems. Here are a few suggestions for troubleshooting:

  • If a peripheral device doesn't work, always check the cables, especially if the device has been working recently.

  • Always check for loose connections.

  • Check for bent or broken pins on the connector. Bent pins can sometimes be repaired; however, they will always be susceptible to damage later, because the pin has been weakened. It is a good idea to mark these connectors and use them with care. A better idea is to replace them.

  • If a connector or cable doesn't fit or if you have to push hard to make the connection, something is wrong. Either a connector has been damaged or it is not the right match.

  • Check for worn or frayed cables. Replace if necessary.

  • Make sure you have the right cable. Some, such as null-modem cables, look just like standard communication cables, but will not work with a modem.

  • Always be wary of "homemade" cables.

Summary of Connectors

Computers use a large variety of connectors for various peripherals. The following table offers a summary of the most common connectors and their uses.

Name Uses
DB-9 Serial ports-external modem, mouse, printer.
DB-25 Parallel port-printer, scanner, removable drive.
RJ-11 Standard telephone connector-2 wires.
RJ-12 Standard telephone connector-4 wires-used with dual phone connections.
RJ-45 Network connector.
PS/2 (mini-DIN) Mouse, scanners.
Centronics Printers.
USB Universal serial bus-Technology that allows multiple peripherals to be attached to one cable. Popular devices are keyboards, mouse devices, modems, video cameras, and Zip drives.

Lesson Summary

The following points summarize the main elements of this lesson:

  • There are many different types of computer cables and connectors. It is important for the computer technician to be able to identify each of them.
  • The evolution of a technology often brings modification to cables, the way they are wired, and their length.
  • Distinguishing between a male or a female connector is often the key to identifying the connector's function.
  • Loose or poorly connected cables are often the cause of computer problems.