说明：  1.1 绪 言 一、信号的概念 二、系统的概念 1.2 信号的描述与分类 一、信号的描述 二、信号的分类 1.3 信号的基本运算 一、加法和乘法 二、时间变换 1.4 阶跃函数和冲激函数 一、阶跃函数 二、冲激函数
(1.1 Introduction of a signal of the concept of the Second, the system the concept of 1.2 signals a description and classification, the description of the second signal, the signal classification of 1.3 signals a basic arithmetic, addition and multiplication Second, the time step function transform 1.4 and Impulse Function First, the Second step function, impulse function)