Many cable box's won't pass through the original signal. You can split the coax before the cable box and go to both, at which point you can use the TV's tuner for any analog cable channels. If the goal is to watch a digital cable channel (my 2-year-old daughter watches Noggin some on the weekends) or features like On Demand or DVR, then you can use the cable box's coax output, set the TV on channel 3 or 4, and use the cable box. At that point, you could also (possibly more easily) use composite or s-video and analog audio from the cable box to the TV and have the same result.