A clamp, including: a first clamp body, having a first jaw which is electrically conductive; a second clamp body, pivoted with the first clamp body and having a second jaw being pivotable relative to the first jaw; a first elastic member, two ends of the first elastic member abutted respectively against the first clamp body and the second clamp body so that the first jaw of the first clamp body and the second jaw of the second clamp body are biased toward each other; a conductive bridge mechanism, configured to be electrically connected with an electrode, including a reciprocating assembly, an elastic engaging element and an operable portion, the elastic engaging element disposed between the reciprocating assembly and the operable portion, the elastic engaging element and the reciprocating assembly being individually separate members, the elastic engaging element being movable toward the reciprocating assembly, the reciprocating assembly being movable toward the elastic engaging element and being positionally engageable with the elastic engaging element through an elastic reverse movement of the elastic engaging element, which is a movement away from the reciprocating assembly, the reciprocating assembly having a first end connected to the first jaw and a second end configured to engage with the elastic engaging element, the reciprocating assembly being movable between a first position and a second position, the elastic engaging element being movable between a third position and a fourth position, the operable portion being movable between a fifth position and a sixth position; and an alarm device, electrically connected, in series, with and between the first jaw and the conductive bridge mechanism; wherein, when the reciprocating assembly is located in the second position, the operable portion is located in the fifth position and the elastic engaging element is located in the third position, the reciprocating assembly is configured to be blocked by the elastic engaging element in the second position, wherein the first jaw and the electrode are electrically connected via the reciprocating assembly; and wherein, when the elastic engaging element is located in the fourth position, the reciprocating assembly is configured such that it is not blocked by the elastic engaging element and biased to the first position, wherein the first jaw and the electrode are not electrically connected; wherein the elastic engaging element and the first clamp body form a compression space therebetween; wherein the elastic engaging element is configured to be compressed toward the compression space to retractably extend toward the reciprocating assembly. a first clamp body, having a first jaw which is electrically conductive; a second clamp body, pivoted with the first clamp body and having a second jaw being pivotable relative to the first jaw; a first elastic member, two ends of the first elastic member abutted respectively against the first clamp body and the second clamp body so that the first jaw of the first clamp body and the second jaw of the second clamp body are biased toward each other; a conductive bridge mechanism, configured to be electrically connected with an electrode, including a reciprocating assembly, an elastic engaging element and an operable portion, the elastic engaging element disposed between the reciprocating assembly and the operable portion, the elastic engaging element and the reciprocating assembly being individually separate members, the elastic engaging element being movable toward the reciprocating assembly, the reciprocating assembly being movable toward the elastic engaging element and being positionally engageable with the elastic engaging element through an elastic reverse movement of the elastic engaging element, which is a movement away from the reciprocating assembly, the reciprocating assembly having a first end connected to the first jaw and a second end configured to engage with the elastic engaging element, the reciprocating assembly being movable between a first position and a second position, the elastic engaging element being movable between a third position and a fourth position, the operable portion being movable between a fifth position and a sixth position; and an alarm device, electrically connected, in series, with and between the first jaw and the conductive bridge mechanism; wherein, when the reciprocating assembly is located in the second position, the operable portion is located in the fifth position and the elastic engaging element is located in the third position, the reciprocating assembly is configured to be blocked by the elastic engaging element in the second position, wherein the first jaw and the electrode are electrically connected via the reciprocating assembly; and wherein, when the elastic engaging element is located in the fourth position, the reciprocating assembly is configured such that it is not blocked by the elastic engaging element and biased to the first position, wherein the first jaw and the electrode are not electrically connected; wherein the elastic engaging element and the first clamp body form a compression space therebetween; wherein the elastic engaging element is configured to be compressed toward the compression space to retractably extend toward the reciprocating assembly.