Wired keyboards connect using a serial port, either by a traditional five-pin serial connection or using a USB cable. The keyboard would receive power over this cable and transmit the commands to the PC. A wireless keyboard is powered by battery and sends its signal to a receiver that is connected to the PC through a USB port.
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How does the keyboard get power?
How does the computer get the information?
A radio frequency (RF) receiver, like the one pictured, or a Bluetooth antenna receives the information transmitted to it from the keyboard. Microsoft Windows and Apple Computer's operating systems each have the ability to translate the commands sent wirelessly.
Benefits and limitations
Wireless keyboards permit users to work up to 10 feet from their receivers. This is helpful if you have a large workspace or work at a bank of monitors. On the flip side, the further away the keyboard sits from the receiver, the greater chance of delay or keystrokes being dropped from input. In addition, RF keyboards can interfere with other wireless devices in close proximity.