I use this circuit as telephone ring detector, but I can’t get a pulse at pin 5 when the phone rings. When there is no incoming call, the voltage at pin 5 is 5V. When the phone rings, the voltage drops to 3V instead of 0V. Anyone can tell me how to solve this problem to get a ring pulse? What is voltage at pin 5 I should get when there is no phone ring? 5V or 0V?
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