All power circuits and electric equipment shall be de-energized before work is done on them: Provided, That qualified employes may, where necessary, make necessary attachments or connections to energized trolley wires if they wear insulated shoes and lineman's gloves. Gloves or mats of rubber or other suitable insulating material shall be provided and used by qualified persons, so engaged, to de-energize or energize circuits of medium or high voltage when other than remotely connected.