I be a Comcast customer . as most know , Comcast 's service be HORRIBLE . after make several appointment for service due to fuzzy picture in my upstairs bedroom , a Comcast service contractor finally arrive at my doorstep . after look at my four upstairs television , he basically tell I that I need a signal booster . I buy the Motorola 4-port bda-s4 amp . it work like a charm . all of my upstairs television now have extremely clear picture and sound . do not bother call the cable guy . if you have a problem with signal , buy one of these . it 'll likely fix you problem .