９０年代中前期，是中国电信建设迅猛发展的孕育期。在这一期间内，市场需求高速增长与电信建设状况矛盾日益突出，市场的繁荣加速了新技术的应用过程。在交换领域，中国已逐步完成模拟制式到数字程控制式的转变，传输网络也在这一时期确立了将由ＰＤＨ向ＳＤＨ过渡的共识... The early 90s, is the rapid development of China’s telecommunications construction period. During this period, the contradiction between the rapid growth of market demand and the state of telecom construction has become increasingly prominent. The prosperity of the market has accelerated the application process of new technologies. In the field of exchange, China has gradually completed the conversion from analog format to digital range control mode, and the transmission network has also established a consensus during this period of transition from PDH to SDH ...