When electricity flows through a wire, it generates electromagnetic waves. Forming the wire into a coil around an iron core will produce an electromagnet.
When an oscillating electric current is pumped into an antenna, a set of electromagnetic waves are generated at the oscillating frequency corresponding to that of the electric current. These waves are propagated through space.
When these waves encounter another wire – the receiving antenna – some of the energy is absorbed, and converted back into electricity. A receiving antenna can be tuned to accept only waves of a certain frequency. In an stereo or TV system, the tuning is variable to allow the tuner to receive many different radio or TV stations, each transmitting on its specified frequency range. Cell phones also work on this principal, with the individual cell phone also transmitting back to the tower in a two way communication.
Wifi & Bluetooth
But this applies to otherwireless inter-computer communications as well. So your smartphone contains both transmission and reception antennas for its cellular communications to your telcom provider, and others for communications for Wifi and Bluetooth.
These last two are the most common forms of wireless communications between electronic devices. Wifi is generally used for medium distance, high-bandwidth connections to the internet. Bluetooth is much shorter range and lower speed. It is used for connecting cell phones to computers, phones or computers to some headsets, and for some wireless keyboards and other peripherals.
In both Wifi and Bluetooth, the signal is manipulated – either the frequency or the amplitude (strength of the signal) is varied – in order to encode the data sent. The transmission frequencies and encoding methods are done according to set specifications so that devices by different manufacturers can talk to each other, what is known as communications protocols.
Once data is received, it is interpreted by a program, a process that may or may not include decryption. The receiving program will then use this data to perform whatever function it was intended to do, perhaps responding with its own transmission. Headphones, for example, will interpret the digital data into an analog set of pulses to the speakers, producing the music. A mouse, on the other hand, aside from connection and acknowledgement signals, is mostly a transmitter to the host computer.
Wifi uses microwaves in the 2.4 GHz and 5 GHz bands. Bluetooth uses short-wavelength UHF radio waves from 2.4 to 2.485 GHz.
So, there are many layers of protocols. There are the physical layers that specify what frequencies are to be used, how the digital data is to be superimposed on the radio signal, and how it is to be electronically decoded. There may or may not be data encryption systems involved at this level. Then there are message packet levels that describe how each packet of data is to be formatted. There is some data for a message ID, a portion set aside to specify the recipient program, and then the message portion of the data. These are software levels that are standardized so that any program can send and receive data via the physical apparatus.
After this, it is up to the receiving program to interpret the data (which again might be encrypted) and display or otherwise use it for its intended purpose.
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