The highest level hub in a hierarchy of hubs. The header hub broadcasts signals transmitted to it by lower level hubs or DTEs, such that they can be received by all DTEs which may be connected to it, either directly or through intermediate hubs.; 套筒式設(shè)備分層結(jié)構(gòu)中最高層的套筒式設(shè)備。套筒式設(shè)備將較低層套筒式設(shè)備或數(shù)據(jù)終端設(shè)備(DTE)發(fā)送給它的信號(hào)進(jìn)行廣播,因而與它相連的所有DTE都可以接收 這種信號(hào),與它相連的所有DTE既可以直接相連,也可以經(jīng)過中間套筒式設(shè)備相連。