Insulation piercing device for testing continuity of electrical circuit

Claim 1

A circuit testing device comprising: a tubular case member formed of a non-conductive material, the case member having a non-conductive hook means at one end thereof adapted to hold a line being tested; a probe means reciprocally movable longitudinally within the case member and having a pointed end movable into contact with a line held by the hook means; trigger means mounted on the case member and connected to the probe means to effect longitudinal movement thereof; a conductive means extending from the case member and having a clamp at the end thereof for connection to the circuit to be tested; a signaling means connected to the conductive means and the probe means; and a conductive extension axially aligned with the probe means and fixedly mounted in an opening in the non-conductive hook means such that upon movement of the probe means to an extended position, when the hook means is not holding a line for testing, the probe means contacts the extension thereby enabling the testing device to be used in testing circuits without the line being tested being located in the hook means, the extension means being out of electrical communication with the remainder of the testing device when the probe means is not in contact with the extension means.