Computer AC power monitoring circuit

Circuit principle: AC power supplies such as computers have large loads, and current transformers are used to detect current. It can be used to detect whether there is current in the power line and determine its working status. LM393 is a Schmitt circuit comparator (A). After the power is turned on, the setting of the alarm time interval is completed by IC1. When binary code is input at the input terminal (A, B, C, D), the time interval of 1C1 can be set. B and D are set to high level , and A and C are set to low level. 1C1 divides the input power frequency by 1/2". If the power frequency is 50Hz, after about 87 minutes, and when the power frequency is 60H, after about 73 minutes, the decoding output terminal (DECODE ()UT) outputs high level , VT1 When it is on, the buzzer HA will sound, and the sound time is determined by RI-I and CH.