Butt sets are handheld devices used for troubleshooting telephone lines. The form factor of a butt set is similar to that of astandard landline telephone. Butt sets even include a keypad for making test calls after connecting to a telephone line. With the help of the butt set's alligator clips stemming from the base of the device, you can tap into a telephone line for troubleshooting.
Connect a modapt to the telephone jack, using the modapt's modular phone cable. Plug one end of the cable into either port on the modapt and then plug the other side of the cable into the telephone jack.
Clip the butt set's red and black leads onto the test pads located along the circumference of the modapt.
Press the "Test Call" or "Hook" button on the butt set. Dial a test number on the butt set's keypad.