普通电话单机因缺少录音功能,难以对通话内容进行录音。但在电话单机上只要加装一个无线发射器,便可在一定范围内用收录机收录通话内容。 电路原理 图1是电话单机加装无线发射器的原理图。L1和L2是电话线,DF是电话单机,S为发射开关。无线发射器由极性保护电路、电源电路和调频发射电路等组成。极性保护电路由VD1～VD4所组成,其作用是将电话线上极性不确定的电压变换为极性确定的电压。电源电路由VD5、VD6、R1和C7组成。线路电压经极性变换后,由VD5稳压,再经VD6和R1降压后,在C7两端得到约2.2V左右的稳定电压,供调频电路使用。调频发射电路由V、C4、L Ordinary phone stand-alone due to lack of recording capabilities, it is difficult to record the call content. However, as long as the installation of a wireless transmitter on a single phone, you can use a tape recorder included in a certain range of call content. Circuit diagram 1 is a single phone installed wireless transmitter schematic. L1 and L2 are telephone lines, DF is a standalone telephone, and S is a transmit switch. Wireless transmitter by the polarity protection circuit, power supply circuit and FM transmitter circuit and other components. Polarity protection circuit is composed of VD1 ~ VD4, its role is to change the polarity of the phone line voltage uncertainty to determine the polarity of the voltage. The power circuit consists of VD5, VD6, R1 and C7. After the line voltage is transformed by polarity, it is regulated by VD5, and then stepped down by VD6 and R1, and then a stable voltage of about 2.2V is obtained at both ends of C7 for the use of the frequency modulation circuit. FM transmitter circuit by the V, C4, L