| 摘要 |
PURPOSE: A device for preventing a door opening by power failure is provided to prevent opening a door resulted from an initialization by prohibiting enabling a relay driver until the initialization is executed, in spite of resupplying power after cutoff. CONSTITUTION: A device for preventing a door opening by power failure through a relay driver according to power's resupply in a key phone system, comprises a Central Processing Unit(CPU)(210), a delay circuit(230), and a relay driver(220). The CPU(210) executes an initialization for the key phone system, when power is resupplied after cutoff. The delay circuit(230) outputs a voltage, pressured partially while the initialization is executing, to an output non-recognizing signal, through a correcting number value of a capacitor(C) and resistor(R) by connecting with the capacitor(C) and resistor(R) between an input of the driving voltage and folding certificated through resupply of power after cutoff. The relay driver(220) keeps a door lock by preventing the relay drive through an initializing data of the CPU, when the output non-recognizing signal is certificated.
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