A detection circuit, configured to detect an earphone plug (122; 132; 142) comprising three or four signal transduction areas (124-127; 134-137; 144-146) arranged by a predetermined sequence along a single pin depending on the type of earphone plug including at least a ground area (125; 134; 144), a right audio-signal area (126; 136; 145) and a left audio-signal area (127; 137; 146), said detection circuit comprising: a first pin and a second pin, configured to connect to one or two of signal transduction areas (124-127; 134-137; 144-146) of the plug; a division voltage-detection circuit, configured to generate a first division voltage and a second division voltage according to the one or two signal transduction area(s) connected by the first pin and the second pin; a processing unit, determining one or two signal transduction area(s) connected by the first pin and the second pin according to the first division voltage and the second division voltage and generating a switch-control signal accordingly; a microphone switch, controlled by the switch-control signal; and a codec, coupled to the microphone output node; characterized in that the microphone switch has a first input terminal coupled to the first pin, a second input terminal coupled to the second pin, a first output terminal coupled to a microphone output node, a second output node coupled to a ground, and a control terminal coupled to the switch-control signal output by the processing unit, wherein the microphone switch is configured to connect the first pin and the second pin respectively to the microphone output node and the ground, when the processing unit determines that the first pin and the second pin are respectively connected to a microphone area and a ground area of the plug, and the microphone switch is configured to connect the first pin and the second pin to the ground and the microphone output node, respectively, when the processing unit determines that the first pin and the second pin are respectively connected to the ground area and the microphone area of the plug. a first pin and a second pin, configured to connect to one or two of signal transduction areas (124-127; 134-137; 144-146) of the plug; a division voltage-detection circuit, configured to generate a first division voltage and a second division voltage according to the one or two signal transduction area(s) connected by the first pin and the second pin; a processing unit, determining one or two signal transduction area(s) connected by the first pin and the second pin according to the first division voltage and the second division voltage and generating a switch-control signal accordingly; a microphone switch, controlled by the switch-control signal; and a codec, coupled to the microphone output node; characterized in that the microphone switch has a first input terminal coupled to the first pin, a second input terminal coupled to the second pin, a first output terminal coupled to a microphone output node, a second output node coupled to a ground, and a control terminal coupled to the switch-control signal output by the processing unit, wherein the microphone switch is configured to connect the first pin and the second pin respectively to the microphone output node and the ground, when the processing unit determines that the first pin and the second pin are respectively connected to a microphone area and a ground area of the plug, and the microphone switch is configured to connect the first pin and the second pin to the ground and the microphone output node, respectively, when the processing unit determines that the first pin and the second pin are respectively connected to the ground area and the microphone area of the plug.