电子自动电话交换机在我国还是一个新事物,研制和运用的时间都比较短。在国际上来说,电子交换机已成为电话交换的主要发展方向,其中以采用存储程序控制、空间分割和金属接点程式的半电子交换机最为普遍。齐齐哈尔铁路局电务修配厂的工人、领导干部和技术人员,为了改变我国铁路电话交换的落后面貌,发扬了独立自主、自力更生的革命精神。1970年首先研制了120门半电子交换机。为了适应铁路运输 Electronic automatic telephone exchange in our country is still a new thing, research and application of time is relatively short. Internationally, electronic exchanges have become the main development direction of telephone exchanges. Among them, semi-electronic exchanges using program control, space division and metal contacts are the most common. In order to change the backwardness of the railway telephone exchange in China, the workers, leading cadres and technical personnel of the Qiqihar Railway Bureau Power Repair Factory carried forward the revolutionary spirit of independence, self-reliance and self-reliance. First developed in 1970, 120 semi-electronic switches. In order to adapt to railway transport