Combining Composite Video Outputs ?

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I have 2 Composite video outputs ( DVD & Set Top Box ) but the TV has only
one Comp. Video IN.
Can I combine them in any way ?  I dont wish to use a switch if I can get
away with it .....to complicated for
other members of household - flicking a switch is fairly high tech !!!

Only one device would be in use at any one time, but power would still be
applied to both units.
Can it be done by just combining the leads ? Can I expect any problems or
even damage ?
Can I knock up a small combiner with minimal components ?


Thanks

Alan




Re: Combining Composite Video Outputs ?


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Assuming you mean only one unit is operating at a time, it'll almost work,
except each video output is designed for 75 ohm load, if you hook up 2
outputs together, as well as the TV, then each output will see 2 x 75 ohm
loads in parallel, or 37.5 ohms, which will overload the output and result
in a poor picture, although the TV may be able to compensate somewhat.

To alleviate this you could use a 33R resistor in series with each of the 2
signals. Note that if you disconnect one of the devices, the picture will
also go bad.



Re: Combining Composite Video Outputs ?



"ALAN GILCHRIST"
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 **  This is nonsensical -   if the STB is powered  all the time then HOW do
you imagine it will NOT come through on the TV screen all the time  ????





...........   Phil




Re: Combining Composite Video Outputs ?


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Mind control?

I'd suggest that if flicking a switch is too high tech for them then turning
on the TV in the first place will be well beyond their ability and hence you
have no problem!

Otherwise, I fail to see any solution other than a switch box, unless the OP
wants to ensure that only one device is ever switched on at a time, even the
'blank' screen will interfere with the picture from the other device......

Another solution - Run the DVD via the VCR AV in to the RF input of the TV
and then the STB to the AV inputs - problem solved!





Re: Combining Composite Video Outputs ?



"Martin, VK2UMJ"

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 ** Yeah -  I figured out this dude must be into prescient switching.


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  **  Arrrrrhhhhhhh !!!

 Running a DVD via a VCRs RF modulator reduces the pic to VHS quality !!





.............    Phil






Re: Combining Composite Video Outputs ?


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Yes, I agree it isn't desirable, but if you don't want to use an AV switch
then you are rather limited in your options...

IMHO the simplest solutions are to either use an AV switch and maintain the
high quality input, or sacrafice that quality and shunt one via the VCR.




Re: Combining Composite Video Outputs ?


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only
get
!!!
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still be

In this case, the answer is most almost certainly NO.
If the STB and DVD are powered up then they will be both be generating
a signal be it a blank screen, menu screen, screen saver etc

You *might* be able to get away with combining the outputs if you only
have one device powered on at a time. But that would require you to use
the power switches accordinly, and that is more complicated than a
simple source switch. If they switch both on at once then you'll most
likely get a grabled display, and then if they'll probably freak out
that they have broken something given that a simple switch is too high
tech for them.

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problems or

Damage, most likely not.

Get a switch box, it's the best solution. Put big DVD & TV labels on,
they'll soon get the hang of it. If they can't figure it out they go
without :->
Even if you got a new TV with multiple inputs, you'd still have to push
a button to select different inputs, so there is no real advantage
there either.

Dave :)


Re: Combining Composite Video Outputs ?



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You can use the RF output of the set top box . its not a bad output on a
small screen TV.

Its only free to air tv after all.

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Nope.


there has to be a switch somewhere, whether on the tv, a manual $15 switch
box,
a VCR...

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Nope. thats still  a switch "must switch this one on  and the other one
off"...


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if they are both on,  you can see one signal with the other picture
scrolling it through it.


And what about sound ? how do you  do the same thing with sound ?

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Nope.

buy a switch.



Re: Combining Composite Video Outputs ?


On Sat, 16 Apr 2005 08:13:35 +0930, "ALAN GILCHRIST"

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you CANNOT do this - the signals wouldnt be syncd and as a result you
would end up with a total mess.  

The switchbox is about the only practical means that I can see to
solve this problem, short of changing over the TV for a newer one with
multiple inputs.




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