Linux Unwired [Electronic resources] نسخه متنی

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.