This is a working old rubber lineman's butt set tester. I connected it to a phone line, turned on the toggle switch, heard dial tone, dialed a phone number using the built-in rotary dial, and spoke to the person who answered on this test set. That is after I replaced the microphone with a brand transistorized microphone of the same type as the original. The leads and alligator clips are in great shape, The dial works smoothly. The toggle switch works great. The belt hanger works fine.