The click to call plugins will turn phone numbers on web pages into clickable links. When clicking the links, the callto: uri is called for external applications like the desktop Interaction Client to handle. It can also use the web client to dial numbers if it is running in another tab.
Extension can be installed from: https://chrome.google.com/webstore/detail/interaction-center-click/dihlakmbcgnjejelioimfmlahhjagfpa