the invention discloses a hinge including a first support , a second support , and a sensor . the first support includes a first electrical connection part . the second support includes a second electrical connection part and a protrusion part , and the protrusion part is insulated from the second electrical connection part . the second support is engaged to the first support , and the second electrical connection part detachably and electrically contacts the first electrical connection part . the sensor is respectively and electrically connected to the first electrical connection part and the second electrical connection part . when the first support rotates to a specific position relative to the second support , the first support and the protrusion part are detached . meanwhile , the sensor correspondingly transmits a signal .