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按《电子制作》96年第2期《电话防盗装置》一文经实际制作,用于防并机盗用线路是可行的,但确也有几点不妥。 1.经实测免提机在免提时电压为16V,所以D3宜用18V以上。 2.按原图装接待机电流达71μA,对线路负载加大,不利并机。将原图中MΩ,1MΩ改为10MΩ就可。 3.按原电路装接,外线打入时,用户能振铃。虽然按原理分析,铃流通过极性保护电路整流成了直流,但由于铃流的频率为
According to the “electronic production” 96, No. 2 “telephone anti-theft device,” a text by the actual production for the anti-parallel misappropriation lines is feasible, but there are indeed a few wrong. 1. The measured hands-free machine hands-free voltage of 16V, so D3 should be used more than 18V. 2. According to the original picture installed standby current up to 71μA, increase the load on the line, adverse and machine. The original MΩ, 1MΩ can be changed to 10MΩ. 3. According to the original circuit connection, outside into, the user can ring. Although analyzed by principle, the ringing current is rectified into the direct current by the polarity protection circuit, but because the frequency of the ringing current is