Patent ID: 8138811

Claim:
A key press detecting circuit for detecting the status of a key (K 1 ), characterized in that it comprising: a discharging circuit ( 1 ) consisting of a Resistor-Capacitor (R 1 , C 1 ) circuit, which is connected to the key (K 1 ) and discharges when the key (K 1 ) is pressed, and a voltage detecting circuit ( 2 ), which is connected to the discharging circuit ( 1 ) and comprises a combination of a first transistor (T 2 ) and a second transistor (T 3 ), wherein when the discharging circuit discharges for a predefined period, the first transistor (T 2 ) will be turned on and outputs a voltage to turn on the second transistor (T 3 ) so that the second transistor (T 3 ) outputs a second signal for a second function, and wherein both the first transistor (T 2 ) and the second transistor (T 3 ) are PNP transistors and the base of the second transistor is connected to the emitter of the first transistor.