Datasheet

Identifying Characteristics of Ports and Cables

Infrared

Increasing numbers of people are getting fed up with being tethered to their computers by

cords. As a result, many computers (especially portable computing devices like laptops and

PDAs) are now using infrared ports to send and receive data. An infrared (IR) port is a

small port on the computer that allows data to be sent and received using electromagnetic

radiation in the infrared band. The infrared port itself is a small, dark square of plastic

(usually a very dark maroon) and can typically be found on the front of a PC or on the side

of a laptop or portable. Figure 1.40 shows an example of an infrared port.

FIGURE 1.40 An infrared port

Infrared ports send and receive data at a very slow rate (the maximum speed on PC

infrared ports is less than 4Mbps). Most infrared ports on PCs that have them support

the Infrared Data Association (IrDA) standard, which outlines a standard way of trans-

mitting and receiving information by infrared so that devices can communicate with

one another.

More information on the IrDA standard can be found at the organization’s

website:

HTTPWWWIRDAORG.

Note that although infrared is a wireless technology, most infrared communications

(especially those that conform to the IrDA standards) are line-of-sight only and take

place within a short distance (typically less than four meters). Infrared is generally used

for point-to-point communications such as controlling the volume on a device with a

handheld remote control.

Audio/Video Jacks

The RCA jack (shown in Figure 1.41) was developed by the RCA Victor Company in the

late 1940s for use with its phonographs. You bought a phonograph, connected the RCA

plug on the back of your phonograph to the RCA jack on the back of your radio or televi-

sion, and used the speaker and ampliﬁer in the radio or television to listen to records. It

made phonographs cheaper to produce and had the added bonus of making sure everyone

had an RCA Victor radio or television (or at the very least, one with the RCA jack on the

back). Either way, RCA made money.

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