A guide to those weird ports on the back of your computer

Question: Can you give me a run-through of the different kinds of ports on the back of computer? I run Windows 98 on a Pentium II 400 MHz computer. —Ray

Answer: Elsewhere, we’ve covered what USB, serial, and parallel ports are. You might want to check out that column titled Computer Ports and Connectors: A Quick Reference. Of course, those are not the only ports on a computer. There are lots more.

Two ports are telecommunications ports. A phone-modem port looks like a standard North American telephone jack. This connects an internal modem to a telephone line. Normally, there are two modem ports side by side on the back of a computer (here’s a picture). The one marked “line” (or with a phone jack symbol) is connected to the wall jack. You have the option to connect the other, marked “phone” (or that has a phone symbol), to phone handset in case you only have one jack near your computer that would otherwise have a handset plugged into it. If your computer doesn’t have an internal modem installed, you will not see these ports on the back of the machine. They will be on the back of an external modem.

For faster Internet connections and for networking, an Ethernet or network port is used. This looks like an oversized North American telephone jack (and this is how it looks). The port connects network cabling to a computer. Cable plugged into this port can lead either to a network hub (a junction box that can wire lots of network cables together), directly to a cable modem or DSL modem (both used for high speed Internet), or to an Internet gateway that shares a fast Internet connection between computers. Most newer computers have one of these ports. They can either be built in or appear on the exposed part of an Ethernet PCI card, which inserts into a slot inside the computer. Data moves through them at speeds of either 10 megabits or 100 megabits, depending on what speed the network card in the computer supports.

You may also see a new kind of connector on some newer computers called an IEEE 1394 port. This port is used to transfer large amounts of data very quickly. Usually, camcorders and other video equipment use this port to get data onto a computer. Data can move across the port at up to 400 megabits per second. Apple invented this technology and had branded it as a “Firewire” port. It was also adopted as an industry standard and is called IEEE 1394 on non-Apple computers. Other companies call it i.link or Lynx. It can be used to connect up to 63 external devices to a machine.

Of course, you probably know what the power connector (this is how this one looks) is for. It usually looks like a three-pronged plug recessed into the computer console. It’s used to attach the gray or black power cable that plugs into a How to choose a power strip.

Another port you might encounter is a Video DB9-15 connector. That’s the port where your video display monitor connects. The connector has 15 holes (picture). It sort of looks like a serial port connector, like a rectangle with two caved in corners, but that port has pins not holes in it.

You’ve probably also encountered a PS/2 port (here it is). This is sometimes called a mouse port. It is used to connect a computer mouse or a keyboard. Most computers come with two PS/2 ports. Sometimes, web cameras piggyback on the ports in conjunction with a parallel port.

For further help, a visual guide about ports with pictures is available on this Web site at: Computer Ports and Connectors: A Quick Reference.