A body of electrically insulating material is provided with a plurality of apertures extending between two surfaces thereof to accommodate an equal number of electrically conductive pins extending from the tube. One of the surfaces of the body of the base is recessed at the location of one of the apertures....http://www.google.com.tw/patents/US4155618?utm_source=gb-gplus-share專利 US4155618 - Base assembly for an electron tube
