Voice over IP is a digital expertise which allows users to make voice phone calls through the internet fairly than using the traditional analogue telephone lines. Some VoIP phone facilities only allow users to make calls to other users of the same services. However, other service providers allow users to make telephone calls to anybody who has a phone number with, long-distance, local, worldwide and mobile number. Some IP phone services work only over computers or special IP phones, while others allow users to use a traditional telephone connected to a VoIP adapter to make calls. IP based phone systems converts the voice signals into digital data packets which are then transferred using the internet. If you call a regular telephone number, these signals are transformed to regular phone signals before they reach the destination.