1.6 Infrared

The electromagnetic (EM) spectrum contains many different wavelengths of which the RF spectrum is a small part. Another part of the EM spectrum is infrared light. This light has a longer wavelength than visible light, but a much shorter wavelength than radio or microwave radiation. Infrared is usually linked to body or mechanical heat, as many objects above room temperature emit infrared radiation. These emissions can be seen by night vision equipment.

Infrared is used in television remote controls, because the signal does not interfere with the TV transmission. Remote controls and Infrared Data (IrDA) equipment utilize light-emitting diodes to emit infrared radiation that is then focused by a lens into a narrow beam. The beam is modulated on and off to encode the data transmission.

The IrDA Association publishes specifications that are used by PDA, notebook, and mobile phone device manufacturers for the infrared ports on their devices. IrDA devices typically have a maximum throughput of 4 Mbps. While most mobile devices still have IrDA, many manufacturers are replacing these with Bluetooth.