Abstract: A plunger of the probe has a slider portion engaged with a plunger guide hole formed in a socket body, which is prevented from rotating, and first and second positioning surfaces having different vertical positions along a central axis of the probe by cutting two places of a rounded bar member in a radial direction. The probe receptacle has a first abutting protrusion on which the first positioning surface is abuttable and a second abutting protrusion on which the second positioning surface is abuttable when the probe is inserted in a correct posture. When the plunger is inserted in an erroneous posture, the first positioning surface abuts on the second abutting protrusion to prevent the plunger from projecting from the plunger guide hole or project the plunger by an amount less than the design dimension.

Abstract: A plunger of the probe has a slider portion engaged with a plunger guide hole formed in a socket body, which is prevented from rotating, and first and second positioning surfaces having different vertical positions along a central axis of the probe by cutting two places of a rounded bar member in a radial direction. The probe receptacle has a first abutting protrusion on which the first positioning surface is abuttable and a second abutting protrusion on which the second positioning surface is abuttable when the probe is inserted in a correct posture. When the plunger is inserted in an erroneous posture, the first positioning surface abuts on the second abutting protrusion to prevent the plunger from projecting from the plunger guide hole or project the plunger by an amount less than the design dimension.