无绳电话机将传统的电话机身和手柄分立成座机和手机两部分,人们可以不再受电话机手柄话绳的限制而在距座机一定范围内受话或拨叫电话,给人们带来了方便。但随着无绳电话用户的增多,相互间的干扰也日益严重,特别是别的手机误控通过自己的座机拨打市话,既影响自己的正常受话(电话打不进来),还增加话费开支。无绳电话的手机和座机之间通过无线信道传输信号,再由座机延伸接通电话线路。由于无线电频率资源有限,按国家无线电管理委员会1985年的规定,分配给无绳电话使的工作频率只有双组频率点,必然有许 Cordless telephones divide the traditional phone body and handle into two parts, a landline phone and a mobile phone, so that people can no longer receive calls or make calls within a certain range from the landline phone because of restrictions of the phone handle cord, bringing people Convenience. However, as the number of cordless phone users increases, interference with each other is also getting worse. In particular, other cell phones are misidentified calling local calls through their landline phones, which affects their normal calls (the phone can not be called) and calls costs. Cordless phones and landlines between the phone through the wireless channel signal transmission, and then extended by the landline phone line. Due to the limited radio frequency resources, according to the provisions of the State Radio Regulatory Commission in 1985, the operating frequency allocated to cordless phones only has two groups of frequency points,