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用户的线路被盗用时本装置可发出干扰声使其无法通话,并且点亮指示灯以提醒用户;用户电话机使用时本装置则自行关机没有任何干扰。电原理如图所示。L1,L2接电话进线,AB接用户的电话机(可数台并机)。当线路空闲时,L1与L2之间的直流电压为50～60V,通过极性保护电路使稳压管D3击穿,BG1饱和,BG2截止。在这种状态下对市话线路的影响可忽略不计。当线路被并机盗用(即L1、L2左侧接入话机)时,L1、L2间的电压
When the user’s line is stolen, the device may make an interference sound to make it unable to talk and light the light to remind the user; when the user’s phone is in use, the device will shut down without any interference. The principle of electricity is shown in the figure. L1, L2 incoming calls into the line, AB then the user’s telephone (several Taiwan and machine). When the line is idle, the DC voltage between L1 and L2 is 50 ~ 60V, the zener diode D3 breaks down through the polarity protection circuit, BG1 is saturated and BG2 is cut off. In this state of the local telephone line can be neglected. When the line is stolen by the parallel (ie, the left side of L1, L2 access to the phone), L1, L2 voltage