Device Connection Types

Devices can be connected to your computer in different ways through many different ports. Look at the back of any modern PC and you’ll find plenty of device ports. Why? Which should you use? One of the reasons there are so many ports is that most computer users have plenty of peripheral devices – everyone has a monitor, a keyboard and a mouse. Most PC users have a printer and a scanner. On top of that there are card readers, connections for digital cameras, mobile phones, external hard drives, portable Mp3 devices, handheld computers…

In the early days of computing the printer went in the printer port, the mouse in the mouse port and so on. Nowadays it’s still possible to connect your devices via these ports, known as serial and parallel ports. More common for connection to a modern, Windows enabled computer is the USB port, with most printers and so on using this connection, and lots of PCs use infrared and Bluetooth connections as well. So which is best?

Generally speaking the newer the device ports the better – USB 2.0 is better than USB 1.1, and both are faster than old fashioned serial ports. The table below shows the data transfer speeds in Megabytes per second of some of main connection types:

Device TypeMB/second
Serial (COM, PS/2)0.02
Parallel (LPT)1.0
IrDA-Control (Infrared)0.009
Bluetooth 1.10.125
Bluetooth 22 to 12
USB 1.11.5
USB 2.060
SCSI (various types SCSI 1-ultra 160)5 - 160
FireWire (IEEE 1394)50
FireWire (IEEE 1394b)100

Speed isn’t the only important factor however, so let’s look at some of the other advantages for your device. Infrared is very popular despite it’s slow data transfer rate This is because things like remote controls or some transfers between handhelds and PCs work really well with this protocol and it’s really convenient – it needs no wires! There are two different standards, one works from 5 meters (5 yards) and another only works for 1.5 meters but is faster. It’s also good for lap tops where you don’t want to be plugging and plugging devices all the time.

Not all devices really need fast connection speeds. Although not a fast connection, the mouse used to plug into the serial port (small rectangular port with plenty of holes for pins) which was replaced by the PS/2 port (the small, round socket with pins at the back of the computer). This is still a popular choice for keyboards and mice because there isn’t a lot data that needs to travel along these connections. Serial ports are reliable and can deal with very long cables (15 meters or yards long).

The USB (Universal Serial Bus) has the big advantage of accepting many device connections at once (apparently 127 devices can be connected in a ‘daisy chain’ of hubs, though I’ve never tested it!). It also supports the handy ‘hot plug and play’ feature. This means you can pull the devices out and reconnect them without having to reboot your PC every time. USB 2.0 is 40 times faster than USB 1.1

Bluetooth is a newer and popular version of the infrared port idea. It doesn’t use infrared however, but radio waves, and works comfortably across distances of ten meters. Bluetooth 2 is much faster than Bluetooth 1.1 and is a good, convenient choice for cell phones, personal computers and some digital cameras.

Finally a word about firewire. The is a very fast protocol designed for devices that need to transfer a lot of data. You tend to see them used for digital video where large amounts of data need to be transferred.

So, there are lots of options for connecting to your PC – by using serial ports for devices like the mouse and keyboard you can free up USB slots. By using Bluetooth you can save yourself from the inconvenience of wires. If you have speed problems you might be using older versions of the device connector and might want to upgrade.