An electrical connector having a receptacle including a receptacle shell and a plug including a plug housing, a coupling nut threaded on the plug housing and engaged with a coupling ring, the coupling nut having threaded engagement with the plug housing and the coupling ring having locking flanges engageable with cooperable locking lands on the receptacle shell, the plug and receptacle being adapted to be fully electrically mated and locked by rotation of the coupling ring through about 90 degrees. An arcuate detent member subtending an angle of about 180 degrees is keyed to the plug housing for relative axial movement of the plug housing, and is received within an annular groove in the coupling ring for resilient forcible selective engagement of opposite radially outwardly enlarged ends of the arcuate detent member with two sets of radially outwardly formed recesses in the coupling ring. When the coupling ring is rotated to the fully locked position of the plug and receptacle means, the ends of the arcuate member are forcibly snapped into one set of recesses to indicate attainment of the locked and fully mated position by sound and by feel. Rotation of the coupling ring in the opposite direction unlocks the plug and receptacle and the enlarged ends of the detent member are released from the first set of recesses to engage a second set of recesses in the coupling ring to audibly and tactilely indicate attainment of the unlocked position. The resilient arcuate member comprises an enlarged center portion forming a key which is designated to mate with and ride in a keyway on the plug housing with an enlarged portion of the keyway defining a dog-leg in the path of the axial travel of the plug housing. The key .[.makes audible contact with a terminal wall of the dog leg.]. .Iadd.momentarily moves out of contact with the plug housing on the key entering the dog-leg .Iaddend.producing an intensified audible snap .Iadd.of the arcuate detent member into the coupling ring recesses .Iaddend.when the fully mated and locked position of the connector is attained.