一、前言 信息是一种资源并且是关键性的资源,信息的扩充、压缩、替代、输送和分享与现代化的通讯系统分不开,随着长途自动化电话业务不断增长和长距离载波系统的发展,当前采用先进的脉冲编码调制通讯体制,它的优点是抗干扰性强、噪声低、畸变小、传输质量高、设备体积小.而这种现代化数字通讯装置能否正常运转的关键,在于电源质 I. Preface Information is a kind of resource and is a key resource. The expansion, compression, substitution, transmission and sharing of information can not be separated from the modern communication system. With the development of long-distance automated telephone service and the development of long-distance carrier system , The current use of advanced pulse code modulation communication system, which has the advantages of strong anti-interference, low noise, small distortion, high transmission quality, small device size and the modern digital communication device is the key to the normal operation of the power supply quality