The test plug provides a quick and easy means of testing drawout case relays or meters without removing them from their cases. The test plug is substituted for the regular connecting plug and there is nothing to disconnect. The XLA12A enables power to be applied to the relay from either a separate source or the source that feeds the equipment. The XLA13A can only be used when a separate source of power is available. 

To insure low-contact resistance the test plug contact fingers are silver plated.