Patent ID: 8307142

Claim:
A card reader for a card, the card reader comprising: a housing; and; a printed circuit board (PCB) received in the housing, the PCB comprising: a universal serial bus (USB) interface to be connected to an electronic device, the USB interface comprising a positive differential pin and a negative differential pin; a card interface to be connected to the card; a control chip; and a normally-closed switch comprising a first terminal connected to the positive differential pin of the USB interface through a first wire, and a second terminal connected to the control chip through a second wire; wherein a length of a circuit path from the positive differential pin of the USB interface to the control chip through the first wire, the normally-closed switch, and the second wire, equals to a length of a third wire connecting the negative differential pin of the USB interface to the control chip; and wherein the normally-closed switch is operable to be switched on or switched off, so as to control connection between the card and the electronic device.