Wireless keyboards can also be called cordless keyboards. There are three major wireless technologies used in keyboard:
• Infrared (IR)
• Proprietary radio frequency(RF)
• Bluetooth

All three technologies use a transceiver connected to the PS/2 or USB ports on the computer. Because many wireless transceivers are designed for use with a mouse and keyboard, PS/2-compatible versions have two cables—one for the mouse port and one for the keyboard port. A USB-compatible transceiver needs only one USB port to handle both devices if the system supports USB Legacy (keyboard) functions. The transceiver attached to the computer draws its power from the port.

The transceiver receives signals from the transceiver built in to the keyboard. These devices require batteries to function; therefore, a common cause of wireless device failure is battery run-down. Early generations of wireless devices used unusual battery types, but most recent products use alkaline AA or AAA batteries. Some wireless keyboards even have built in batteries and rechargeable system. Users don’t have to change batteries if they run out of power.

Although all three technologies rely on battery power, the similarities end there. IR devices have a relatively short range (12ft. maximum) and must have a clear line-of-sight between the input device and transceiver. Signals get interrupted easily by even a sheet of paper.

Because of this, more and more manufacturers use radio waves (RF) for transmission between the device and transceiver. RF-based wireless devices have no line-of-sight problems, but most have a limited range of about 6 ft. from the transmitter

Although RF overcomes line-of-sight issues that can cripple an IR mouse, early versions of RF products had a high potential for interference from other devices and from other devices in use in the same room because of a limited range of channels. Fortunately, improvements in frequency bands used and automatic tuning have enabled all users of a particular type of device to avoid interference with other electronic devices or with each other.

Although most wireless products use proprietary radio transceivers, the Bluetooth wireless standard can now be used by some keyboards and mice,

Bluetooth-enabled devices have an effective range of up to 30ft. and might be compatible with other brands of devices that are also Bluetooth enabled. This could avoid the problem of frequency interference. This is also why Bluetooth keyboards are more expensive than those RF keyboards.

From www.freeopenbook.com