VoIP (Voice over Internet Protocol) is simply the transmission of voice over the internet.
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VoIP has become popular largely because of the great ways to save money compared to the call charges of many phone companies or calling cards.  For International calling, the monetary savings to the consumer by switching to VoIP technology can be enormous.*
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Headsets are the simplest type of accessory for VoIP and you can use it straight out of the package. You can make handsfree calls from your computer, and a headset ensures better sound quality on your calls. 

* Service provider plan dependant