They are obviously not for home setup where you just plug your phone line in the back. There is a lot of equipment needed on the back end to make them work properly. I know the BT one (on the right in the picture) is "supposed" to interface directly into your email client and allow you to place the calls from your PC. You will find them on trader/dealer desks where you have the ability to see and use 100s of different lines from the same turret. They also give you speaker box functionality. Excellent for keeping multiple lines open all the time without the use of handset. (Think multiple voice brokers/or customers, other offices etc.)