KEYPAD UNIT USING RESISTORS, PARTICULARLY FOR REDUCING THE NUMBER OF SIGNAL LINES

摘要

PURPOSE: A keypad unit using a resistor is provided to prevent unnecessary occupancy of a signal input terminal in a controller and facilitate addition of a new function by minimizing the number of signal lines by adopting resistance elements. CONSTITUTION: A keypad unit(310) selects one of input currents each having a different value by switching a power source voltage so as to be applied to a plurality of resistors(R1-R22) according to external selection. An ADC(Analog Digital Converter)(320) receives the selected input current and converts it into a digital signal. A controller(330) determines a control operation according to the digital signal.