Patent ID: 8810518

Claim:
A password input device, comprising: a display unit, comprising: a group of LCD displays; an input unit, comprising: a group of keys corresponding to the LCD displays; and a control unit electrically connected to the group of LCD displays and the group of keys, wherein the keys are positioned on the corresponding LCD displays, the control unit creates a group of numerical key sequences, and controls the LCD displays to display the numerical key sequences through the keys; wherein each LCD display comprises a group of input ports and a common port, the input ports are electrically connected to the control unit to receive command signals, and the common port is electrically connected to the input unit and to the control unit to receive input signals, wherein the keys of the input unit are made of a transparent material, when any key is operated, one end of the key is electrically connected to the common port of the corresponding LCD display, the other end of the key electrically connects between a first resistor and a second resistor, the first resistor is electrically connected to a power source, and the second resistor is electrically connected to ground through a capacitor, and the first resistor, the second resistor, and the capacitor are electrically connected between the power source and ground in series; and wherein the control unit comprises a microcontroller, the microcontroller comprises a group of data pins, and a test pin, the data pins are electrically connected to the input ports of each LCD display respectively, to output command signals to the LCD displays, the test pin is electrically connected between the second resistor and the capacitor to receive voltage signals from the common ports.