Video over Cat5

[sj2as]

I'm trying to install a system using extron vga and serial control over cat5 cable boxes.

 

The gear works perfectly over a single cable, but I would ideally like to have multiple plug in points around the room where the output of the transmitter could be plugged into.

 

I need to somehow 'sum' the four cat5 plug in point cables at the receiver end in order to plug a single RJ45 into the receiver and then output the VGA to the display (50" plasma).

 

I am experiencing lots of reflections when I just try joining the single cores of the cat5s together (which I pretty much expected), but am not sure how to proceed in order to stop the reflections and somehow 'balance' the video signal.

 

I suspect I may be able to use some resistors but hoped someone might already have solved this problem and could advise.

 

Many Thanks

[pstewart]

Hmm... (If I can use that).

 

I don't think you can do it that way.

 

Have you thought about using the Extron MTP SW6 - that will take 6 RJ-45 inputs and you can choose which one, or allow it to auto-switch between them.

 

Philip

[kitlane]

Could you get away with a manual patch panel of some sort? Maybe just terminate each of the four lines to a wall plate socket each and plug into the one you want?

[sj2as]

I like the idea of the SW6, but not sure whether the budget will stretch that far...

 

The screen itself is at quite high level, so it's not really practical for people to have to patch/plug in where the cables terminate behind the screen. Again, the auto-switching on the SW6 would be ideal for this but it's a question of whether I can find a more 'home-made' solution to keep the cost down.

 

I am also thinking about the possibility of having something plugged into the ethercon sockets at each plug in point that isn't in use, like a plug with a resistor circuit within that will attenuate the reflections on the unused lines. Although this will mean the users will have to unplug this in order to plug in the video output, it is at least more practical than doing it at the display.

[dunk_1984]

The screen itself is at quite high level, so it's not really practical for people to have to patch/plug in where the cables terminate behind the screen. Again, the auto-switching on the SW6 would be ideal for this but it's a question of whether I can find a more 'home-made' solution to keep the cost down.

 

I presume Kit meant in a cupboard/out of the way somewhere.

 

Have a cat5 patch bay where all the plug in points terminate and also a feed to the switcher/screen. Then you just patch the socket you are plugging in to, to the screen feed. Very much like an IT installation.

 

This does rely on everyone knowing what they are doing, however is probably less complex than making them remove a terminator, and more importantly replacing said terminator.

[sj2as]

This does rely on everyone knowing what they are doing

 

Unfortunately very unlikely to be the case!

 

They have a small portable equip rack which houses various sources (laptop input, DVD, VHS) and outputs from a switcher scaler to an MTP transmitter. The rack has an ethercon socket mounted on the back which outputs the video/serial signals, allowing the portable rack to be plugged into any of four plug-in points around the room. A single Cat5 runs from each plug-in point to the display screen, where the MTP receiver lives.

 

I'm lookinng for a way to get all four cat5s into the MTP receiver and avoiding the reflections caused by the signal travelling up and down the other 3 cables that aren't in use when the rack is plugged in.

 

I'm trying to avoid them having to do any patching etc, and I suspect that having to unplug/replug a terminator will be somewhat easier considering I'm dealing with a large number of people potentially plugging in the rack. I would just have to supply them with plenty of spares...

 

Anyone got any ideas on what components would be needed to achieve this attenuation across the unused cables?

[bruce]

Forget fafffing around with resistors.

 

Buy, or make up, a simple mechanical switch box. 4 cat5s in, 1 out, with an 8 pole 4-way rotary switch.

Google suggests you can get one here for less than 20 pounds.

http://www.revealcable.co.uk/acatalog/Data...es.html#aAA2367

 

Or (much more expensive) have 4 receivers, and do the switching in the VGA world.

[TomLyall]

I'm lookinng for a way to get all four cat5s into the MTP receiver and avoiding the reflections caused by the signal travelling up and down the other 3 cables that aren't in use when the rack is plugged in.

 

This reads like you're wiring it in a "star" topology, in which case, I can see why you're getting problems, but could you wire it as a radial instead? You'd still get problems if you used a socket nearer to the reciever, but it might have less of an effect. [/guesswork]

 

Failing that, there's the option of providing each socket with a "link out" to the next socket along (preferably with a plug on a captive cable) which wouldn't get lost like a terminator, and would save patching at a remote location.

 

Can you buy normalising RJ45 sockets? I'd guess not, but it would certainly be a neat solution. I can't remember what the device was, but I've seen a DMX output that auto-terminates by using a microswitch mounted behind the socket, not quite sure which bit it worked against, but certainly is possible with a bit of clever engineering.

 

Tom

[sj2as]

Any one have any experience with the MuxLab 500160 vga switcher? I was wondering if this might be a cheaper alternative to the Extron SW6 unit. I'm particularly interested to know if anyone has any thoughts on it passing the VGA and RS232 data?

 

www.muxlab.com/assets/files/datasheets/VE_VGA_4x1_Switcher.pdf

[Pete McCrea]

The only comment I would add is that you will probably need to ensure that you use one manufacturers products throughout the CAT5 chain, as they are often proprietary convertors, which may well prevent the different brands working together.

 

That said I'm sure you were aware of this.