Patent ID: 6424274
Filing Date: 2002-07-23
Classification: H03M

Abstract:
An apparatus, comprising:a keypad, including: a plurality of chained, passive components in series across a known electrical potential; and a plurality of key switches, each of the plurality of key switches tied to a common node at a first terminal thereof and tapping the chained passive components at a second node thereof, each of the key switches generating a signal indicative of the respective key switch being pressed when the key switch is pressed; and an integrated circuit capable of receiving the generated signal, the integrated circuit including: means for identifying a pushed key from a voltage signal generated by the keypad and received over the first voltage line, the voltage signal having a magnitude indicative of which key switch is being pressed, and generating an output signal indicating the identification; and a control circuit capable of receiving the output signal and capable of, in response thereto, generating a fist control signal to operate a second plurality of N key switches.