Making Things Talk

WIRELESS COMMUNICATION 179

Two Flavors of Wireless: Infrared and Radio

There are two common types of wireless communication in most people’s lives: infrared

light communication and radio communication. The main difference between them

from a user’s or developer’s position is their directionality.

Television remote controls typically use infrared (IR) com-

munication. Unlike radio, it’s dependent on the orientation

between transmitter and receiver. There must be a clear

line of sight between the two. Sometimes IR can work by

bouncing the beam off another surface, but it’s not as

reliable. Ultimately, the receiver is an optical device, so it

has to “see” the signal. Car door openers, mobile phones,

garage door remote controls, and many other devices

use radio. All of these work whether the transmitter and

receiver are facing each other or not. They can even

operate through walls, in some cases. In other words, their

transmission is omnidirectional. Generally, IR is used for

short-range line-of sight applications, and radio is used for

everything else.

Transmitters, Receivers,

and Transceivers

There are three types of devices common to both IR and

RF systems: transmitters, which send a signal, but can’t

receive one; receivers, which can receive a signal, but can’t

send one; and transceivers, which can do both. You may

wonder why everything isn’t a transceiver, as it’s the most

flexible ...