The bandwidth of the copper in addition hawser itself is limited , and placed restrictions on many media need to access the broad width network : like videophone , large data transmitting , videotext etc . 再加之铜缆本身的带宽有限，限制了许多需要较大带宽的业务的接入：如可视电话、大容量的数据业务、可视图文等等。
