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Background: I have a normal CCTV camera (650 TVL) . It requires a BNC cable in order to feed video signal from camera to DVR.

Problem The problem is I have only a single copper wire from CCTV to DVR. The wire which is to be used for the transmission has no shield. It is normal spare copper wire used for household electricity (AC). This is a spare wire and does not have AC current in it.

My Understanding I think that the two wires used in a BNC cable (one core and other shield) can be multiplexed and feed to a single wire

So my question is can I multiplex the signals of two wires of a BNC cable, transmit over a single copper wire and at DVR side reverse the process (i.e. demultiplex the signals and feed to DVR)

Will this work? If yes then can someone please give a head start on how to proceed in order to make or buy such mux/de-mux.

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    \$\begingroup\$ Use two RF modulators on different frequencies. And of course the corresponding demodulators on the other end. \$\endgroup\$
    – Cornelius
    May 15, 2014 at 10:28
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    \$\begingroup\$ As Cornelius says you can do that, although an e-bay search for "2 Channel Video Multiplexer" seems to list a lot of products that would be easier and probably cheaper. \$\endgroup\$
    – PeterJ
    May 15, 2014 at 10:30
  • \$\begingroup\$ @PeterJ the devices listed on ebay requires two wires or a BNC cable to transmit multiplexed signal but in my case I have only a single core wire. \$\endgroup\$
    – Deepak
    May 15, 2014 at 11:04
  • \$\begingroup\$ @Cornelius can you pleae elaborate on how to design such system. I am a s/w engineer by trade but never implemented such system in practical. \$\endgroup\$
    – Deepak
    May 15, 2014 at 11:07
  • \$\begingroup\$ @Deepak, wouldn't your cable have a shield though? So the core is one wire and the shield is another. \$\endgroup\$
    – PeterJ
    May 15, 2014 at 11:12

2 Answers 2

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The two wires of BNC are not different signals, they are "signal" and "shield". The shield is connected to "ground", and serves to keep the signal clean and inside the cable.

For short distances, you can tie the shield to mains earth at both ends and use your single bare cable. This may introduce interference on nearby TVs.

How long is a short distance? I'd expect 10cm to work, 1m to work with some "snow" interference, and 10m not to work very well.

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  • \$\begingroup\$ The distance is > 10 m. So this means that it will not work. Though I have one question :in past I used some chinese device that claimed to convert a CCTV camera into wireless camera. the device had configurable frequencies and this device worked, so how it worked ? \$\endgroup\$
    – Deepak
    May 15, 2014 at 12:26
  • \$\begingroup\$ Either (1) turn it into a TV signal and broadcast on unused channel or (2) digitise the video and send it on the 2.4GHz band (similar to wifi). \$\endgroup\$
    – pjc50
    May 15, 2014 at 12:41
  • \$\begingroup\$ ok. Thanks for the reason. Now I got a clear picture of the problem. \$\endgroup\$
    – Deepak
    May 15, 2014 at 12:50
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No, you can't do that. Electricity always needs a complete circuit, or loop, to flow around, which means that to connect two locations you always need at least two separate conductors.

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