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b.无人值守录音时(参见图3),外线TIP、RING端输入的信号经D621—D624极性转换二极管、RL1继电器动合接点、R649、R606、R609、R613、C635送入U3B(LM324)的⑥脚滤波放大后从⑦脚输出,经C644、B618、U4A(CD4066)电子开关的①、②脚、C629、R639送放U3C的⑩脚,整形后从⑧脚输出,经C641、R638从VFX1一端经J2插头送编码芯片IC702(KT8554)的(15)脚,电路如图4所示。经编码后的数字信号从(11)脚输出送IC701(Z89C67)微处理芯片的
b. unattended recording (see Figure 3), the external TIP, RING input signal through the D621-D624 polarity conversion diode, RL1 relay contact, R649, R606, R609, R613, C635 into the U3B (LM324 ) ⑥ pin filter amplification output from the ⑦ feet, the C644, B618, U4A (CD4066) electronic switch ①, ② feet, C629, R639 delivery U3C ⑩ feet, plastic output from the ⑧ feet, the C641, R638 From the end of VFX1 through J2 plug to send coding chip IC702 (KT8554) of the (15) feet, the circuit shown in Figure 4. The encoded digital signal from the (11) pin output to the IC701 (Z89C67) micro-processing chip