从50年代出现共用天线电视系统以来,60年代美国和加拿大等国就在共用天线系统的基础上开始建立城镇型电缆电视系统。今天,美国几乎过半数的电视家庭都使用电缆电视收看,加拿大则已超过70％。但是一些主要的欧洲国家和日本在70年代后期才开始建立城镇型电缆电视,在这之前重点是发展全频道型共用天线系统。所以,目前一些先进国家都有一定数量的城镇电缆电视系统,并且还在以较高的 Since the common antenna television system emerged in the 1950s, the United States and Canada in the 1960s started to establish urban cable television systems based on the common antenna system. Today, almost half of all television households in the United States use cable television, while Canada is over 70%. However, some major European countries and Japan did not start to build urban-based cable television until the late 1970s, until then, focusing on the development of all-channel shared antenna systems. Therefore, at present, some advanced countries have a certain number of urban cable television systems, and are still using higher