“Extension” - is the extension of the telephone line (PBX) or the Centrex system. It works as an association and allows calling to certain telephone sets without the necessity of dialing the telephone number, but only by dialing a short combination of digits, reaching the desired subscriber.
VoiceIP-USA Incorporation a company incorporated in USA ,whose registered address is World Trade Centre Delaware, 802 West Street, Suite 105, Wilmington, Delaware 19801