The fluke 1664 fc installation tester is the only tester with insulation pretest if the tester detects that an appliance is connected to the system under test it stops the insulation test helping eliminate accidental damage the 1664 fc also gives you fluke connect so you can send test results to your smartphone and collaborate with others auto test makes performs seven tests with one press of the button reducing the number of manual connections and decreasing the possibility of making