一、概述多频信号系统的应用,在长途自动化中早已比较普遍,近年来在市内电话的纵横交换机之间亦逐渐采用。采用多频互控信号所用的多频信号接收器都是模拟电路。从目前国内的情况看,这种接收器存在两个方面的问题。一是设备较庞大。对于纵横制市话局而言,一般12～16对绳路即需要配备一套多频信号接收器;另外,由于多频信号的频率低,频率间隔为120赫,因此模拟滤波器的制作调测有一定困难。二是模拟多频信号接收器不便于在数字 First, an overview The application of multi-frequency signal system, has long been in the long-distance automation has become more common in recent years in the city between the vertical and horizontal telephone switches also gradually adopted. Multi-frequency signal receiver using multi-frequency mutual control signals are analog circuits. From the current domestic situation, there are two aspects of this receiver problems. First, the larger equipment. As for the cross-tracked local telephone exchange, generally 12 to 16 pairs of ropes need to be equipped with a multi-frequency signal receiver. In addition, since the frequency of multi-frequency signals is low and the frequency interval is 120 Hz, the production of an analog filter Have some difficulties. Second, analog multi-frequency signal receiver is not easy in the digital