The way to know for sure is to try it. If it works, then great... if not, you could still split the output from your cable box in the living room and use your box to watch TV in the bedroom. I do that in my office with a 50 foot HDMI cable: I can watch TV at my computer desk or in my living room using just the one box.
is both right and wrong... There are two types of signals carried over cable wires. One is the standard, analog TV signal we all know and love. It's slightly different in different parts of the world, but in all cases, it's exactly the same as what you'd get with an over-the-air antenna before the DTV switchover. The second type of signal is a digital TV signal. Unlike the over-the-air signal, cable companies use a different form of modulation for cable-based DTV; this format provides more data bandwidth for the same RF bandwidth. Your cable box actually does 3 different jobs: it provides a physical tuner, a digital decoder, and a decryption module. Analog signals are decoded and passed through to your television set. Digital signals are decrypted, then decoded, and the resultant images are sent to your TV.Now this is where things can be different: older, analog cable systems could be used directly on your TV, and they allowed you to view around 70 or so channels directly, without the need for a cable box. Later, when cable systems started going digital, the cable companies converted many of the channels to digital, and the digital channels required a digital cable box. However, you could still get the few, remaining analog channels on a TV without the need for a box. Later, some cable companies went all-digital.So the question is... does your cable company still have some analog channels? If it does, it'll probably be the same channels you can get over the air, along with a few other basic channels. Here in the US, we call that "broadcast basic", and the last time I checked, the FCC required cable companies to carry the local broadcast channels unencrypted, so that a standard TV set can pick them up. Carriers could opt to go all-digital, but they had to provide free basic cable boxes to customers who wanted them.The way to know for sure is to try it. If it works, then great... if not, you could still split the output from your cable box in the living room and use your box to watch TV in the bedroom. I do that in my office with a 50 foot HDMI cable: I can watch TV at my computer desk or in my living room using just the one box.