A high voltage power transmission system includes an insulator arranged to electrically isolate a live power transmission line and a testing device in physical contact with the insulator, The teat device measures properties of the insulator by conducting electrical tests of andor optical examination on the insulator while it is in-service to electrically isolate the live power transmission line. The first circuit receives an input signal and switches first and second nodes to opposite states within a first voltage range between first and second supply voltages. A distal stem portion of the implant is affixed onto the stem inserter.