If you are connecting the Lifeline Service using a cable modem, these photos display the proper connection scenarios.
Cable Modem Setup 1: Lifeline Communicator and Cable Modem
Cable Modem Setup 2: Lifeline Communicator, Cable Modem and Personal Phone
Connecting a phone or other device is optional and not required for your Lifeline Service to work. However, if you are connecting a phone it should be plugged into the Communicator's Auxiliary phone jack.