Is there a specification for this? Like, say, at the backside of a cable box there exists a singular coaxial cable that is meant to be plugged directly in the back of the TV.

The TV must be set to a certain "mode" somehow ... I want to know the basic understanding of how the cable box sends video/audio signals through the wire, under what terms/specifications it does so, and how the TV "knows" what to do from there on.

This is a little vague, I know, but any basic answer regarding this will be appreciated.

I basically want to know how "picture data" and "sound data" get carried through that wire, and under what basic conditions this works(hobbyist engineer who is avid on learning all of this stuff, and implementing it).

I surmised that maybe the cable's video/audio circuit connects or transfers video/audio data to a specific form for the coaxial wire, and the TV can intercept and render that somehow? I don't know, this is why I ask, and this is an engineering site!

Thanks in advance for any help!

  • \$\begingroup\$ Phew, I'm glad you didn't ask about how it gets to the TV antenna without using wires. Is this a question about how a TV works or how data is transmitted and recovered? \$\endgroup\$ – Andy aka Nov 17 '13 at 0:22

This wikipedia article covers most of the aspects of how analog television works: http://en.wikipedia.org/wiki/Analog_television

I will give a brief summary, though.

The picture is formed with a series of horizontal scan lines. Sometimes you will see TVs or cameras advertized with a certain number of 'lines' of resolution - this is why. You don't get pixels until you're talking about a digital signal. The lines are transmitted serially one at a time. In the days of CRT televisions, the lines would be sent to the electron guns in the TV as they arrived and the electron gun would draw the line on the screen. Nowadays, the TV just digitizes the signal and dumps it in a buffer.

Audio and video are transmitted as two separate signals. In the case of cable TV and broadcast TV, both signals are modulated onto carrier waves, with different carrier waves for each channel and a known offset between the video and audio carriers. Then the TV can tune into a channel just by picking the correct video and audio carrier frequencies and demodulating the signals.


The simple answer is that, assuming you mean the antenna socket, then the cable box is sending radio waves with the signal encoded as per the normal TV transmission.

There are no special modes.

  • 1
    \$\begingroup\$ This answer is simple to the point of not answering anything. \$\endgroup\$ – Samuel Nov 16 '13 at 23:52
  • \$\begingroup\$ This answers the simple question about how a cable box gets a picture to a TV. It's a simple answer that would enable the OP to ask or seek more useful information. The idea that a TV antenna has "modes" is a simple question. Why think there is a different mode for direct connection vs an TV / RF transmission? But if you don't know then it is a valid question. It is clearly implied the OP thinks that the antenna circuit switched from RF to TV picture only mode. Asking google/wiki how a TV transmission works as the other answer shows is very simple once you know you need a small RF transmitter. \$\endgroup\$ – Spoon Nov 17 '13 at 0:15
  • \$\begingroup\$ It seems all you have done is vaguely introduce the antenna (which was not part of the question) and say, "it works the same way as that". \$\endgroup\$ – Samuel Nov 17 '13 at 2:18
  • \$\begingroup\$ The OP stated "The TV must be set to a certain "mode" somehow ..." which to me implies the antenna socket must have at least 2 modes. Stating it does not use a special mode and it uses the same method as in normal operation prevents the OP from wasting time looking for some special method for a wire only connection. Think of it as looking for a de-bug mode. This is not a rare feature of equipment now. Back in 1930's they didn't have de-bug modes on any equipment that I am aware of let a lone TVs made of tubes \$\endgroup\$ – Spoon Nov 17 '13 at 9:43

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