Patent ID: 7248707

Claim:
A plug detection circuit, disposed in a electronics device with an earphone jack, wherein the eat-phone jack has at least a first pin, a second pin and a third pin, the detection circuit comprising: a first resistor electrically coupled to a voltage source and the first pin respectively; a second resistor electrically coupled to the first pin; a first capacitor having one end electrically coupled to a first output terminal with the second resistor, and the other end coupled to ground, wherein the potential at the first output terminal is a first logic potential; a third resistor having one end electrically coupled to the third pin; a fourth resistor electrically coupled to the voltage source and the second pin respectively; a fifth resistor having one end electrically coupled to the second pin; a second capacitor having one end electrically coupled to the fifth resistor, and the other end coupled to ground; a sixth resistor having one end electrically coupled to the voltage source; and a switch having one end electrically coupled to the sixth resistor, and the other end coupled to ground, wherein the switch further has a control terminal electrically coupled to a second output terminal with the second capacitor and the fifth resistor, and the potential at the second output terminal is a second logic potential.