The signal is modulated and demodulated when it is transmitted . we take some measures such as anti - jamming and rejection of attenuation to make sure of reliability of communication 由于采集点较为分散，距离较远，在信号传输时，我们传输信号进行调制解调，并增加了抗干扰、抗衰减措施保证通讯系统的可靠性。
2.
This paper mainly discusses the design principles and chief techniques of a digital accessing system for power - line communication net ( plcn ) . the technology of low bit rate speech compression high - speed modem based on plcn adaptive equalization to the channel anti - jamming and anti - fading are applied in this system . so speech tele - control data and tele - protection signals can be transmitted high quality in the band - limited channel 该系统综合应用了低比特率语音信号压缩编码技术、基于电力通信网的高速调制解调技术、信号传输的信道自适应均衡技术和抗干扰、抗衰减技术，可在带限信道中高质量的传输语音、远动数据和远方保护等信号，具有较高的整体性能。
