The Panasonic KX-TDA0174 / 0177 / 6174 16-Port Single Line Extension Card IP-PBX is a phone switching system designed for business and industrial offices. This conventional system is manufactured by Panasonic in the United States and is designed to expand the capabilities of a single line phone system. The 16-port extension card allows businesses to easily add more phone lines and features, providing a versatile and efficient communication solution for various office needs.