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随着无绳电话机用户的增多,相互间的干扰也日益严重,特别是他人的手持机误控自己的座机拨打市话,不仅影响自己的正常通话,又增加了话费。 无绳电话机的手持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的规定,分配给无绳电话机的工作频率只有22组频率点,这样必然有许多无绳电话机是在同一频率点上工作的,因此造成无绳电话机的保密性差且互相干扰。为了实现手持机对座机的控制,手持机上会产生一种几KHz的工作导频信号,与通话信号一起对高频载频进行调制后发射出去。座机接收解调并经分离得到导频信号,如果这个导频信号的频
As the number of cordless telephone users increases, interference with each other is also increasingly serious, especially when someone’s handset mistakenly controls his or her landline to dial a local call, which not only affects his normal call but also increases the bill. Between the handset of the cordless telephone and the base unit, the signal is transmitted via the wireless channel and then the telephone line is extended by the base unit. Due to the limited radio-frequency resources, the operating frequency assigned to cordless telephones, as mandated by the National Radio Regulatory Commission, was set at a frequency of only 22 frequencies, necessitating that many cordless telephones operate at the same frequency, resulting in Confidentiality is poor and interfere with each other. In order to realize the control of the handset on the landline, a working pilot signal of several KHz will be generated on the handset, and the high frequency carrier frequency is modulated with the call signal and then transmitted. The base unit receives the demodulation and separates the pilot signal if the frequency of the pilot signal