Which pairs are used for what?

[martynah]

Hi folks.
As the king of bizarre questions I have this one:

I'm about to re-plumb my KAT5 Mk2's to pump my FreeSat HD box'es output to my kitchen TV on composite. (FoxSatHDR downscales HD to the compsite so you can feed HDMI in HD and Composite in standard def at the same time )

Question is, I have a faulty pair in my CAT5 cabling to the tv in the kitchen, without getting the bolster chisel out and redecorating, divorced etc, is it possible to wire the plugs up such that the pair that is not connected is the one that carries the 'spare' channel on the KAT5 that isnt used for composite video? (e.g luminance?) so I can still get stereo audio, Composite and IR? , or am I out of luck? -- I dreamt once that there were 4 signal channels on the KAT5 plus the IR, so I guess I'm asking which is what?

Is there any hope of a functional link with my duff pair? lol.

Cheers.

Mart.

[katman]

Hi Mart,

The pairs in a CAT5 cable are used as follows

Blue (4&5) Left Audio
Orange (1&2) Composite Video/S-Video Luma
Green (3&6) Right Audio
Brown (7&8) S-Video Chroma

The IR channel is carried as a phantom signal over the left and right audio pairs

The SCART Control signals are carried as a phantom signal over the video pairs.

As long as you have three working pairs and connect them to 1&2, 3&6, 4&5 you will be able to get your KAT5 units working with Stereo Audio, Composite Video and IR Passback.

You will almost certainly lose the SCART control feature although there is a faint possibility that it will still work if one wire of the damaged pair is intact. You may get a slight bit of picture disturbance momentarily when the SCART status changes but if you dont have SCART switching signals fed to the transmitter then no data would be sent so that wouldnt be a problem.

Hopefully that solves your problem and that I have explained it clearly enough. Any problems drop me an email and I will be happy to discuss it over the phone if that would be easier.

keith at diyha dot co dot uk

Regards

Keith

[martynah]

Thanks Keith - that's perfect, just what I wanted to know.

I dont use scart switching, and the FoxSat HDR is using composite on a phono feed , and finally - the kitchen LCD is 4:3 anyway! - so it wont even know!

So, your post is perfect! - thanks.

I've put away the bolster chisel! - lesson to all, when building, run DUCTING so you can replace cables 8-)

Mart.

[katman]

Actually, depending on the TV and the HDR, you may find that Aspect ratio switching works anyway.

I have a 4:3 LCD TV in the bathroom fed by KAT5 into the S-Video input (Scart on that TV only supports Composite and RGB) and if I use SKY as the source, it picks up the Line 23 Widescreen Switching signal and maintains the correct aspect