This is the US equivalent of the original British patent GB-1,445,977."A probe for determining at what point in space contact is made between an object and a stylus. The stylus is located in an accurately defined rest position relative to a housing and slight deflection of the stylus away from this rest position is detected preferably by electrical switches."This patent covers a key innovation that enabled easier and more accurate CNC machining. McMurtry's invention led to the creation of Renishaw plc, a specialist in CNC measurement devices with other product lines related to metrology and spectroscopy.