2-Line Integrated Phone System with Intercom, Hearing Aid Compatible (HAC), Call Waiting Caller ID and Speakerphone, Black...With two-line operation, you can conference in two outside lines to have a three-way conversation. Or place your current call on hold to make another call. Being able to use two phone lines with just one phone makes it convenient and efficient to manage your calls. So you're going out with two of your friends tonight, but you're having trouble deciding where to go. Make it easy on yourself and talk to both of them at the same time. With up to 3-way conferencing, you can talk to two outside lines at the same time.