Beijing telecom had to make its decision on the basis of the energetic development of its basic transfer network , instead of rendering it an accessory to switching . as a result , a basic unit of the transfer network of 155 mbits ( hereinafter referred to as stm - 1 ) is added so that e1s and stm - 1s coexist . the pstn and the internet prefer stm - 1 connections at the tandem exchanges , high - capacity end exchanges of users and backbone convergence points 加大传输网、光缆网的发展力度，基础传送网超前发展，不能再作交换的"附庸" ，已成为公司决策的出发点；传输网的基本单位要增加155mbits （下称stm - 1 ）为单元的基本单位， e1和stm - 1并存；电话交换网和因特网在汇接局、大容量用户端局和骨干会聚点以stm - 1连接为首选。
