[vdr] Re: 2 TVs and 2 RemoteControls

[Thomas Breuer <tb@tb-electronic.de>]

On 23/01/2003 18:38 Emil Naepflein wrote:

> The normal output seems to be terminated and the signals from J2 are
> not. So I assume that there is some kind of amplifier in between which
> separates the signals. But, I may be wrong.

As Ulrich said it comes from the same AV711x pin. There is only a
passive pi-filter (2 caps and one inductor) between the output pin and
the cinch video output, and there is no 75 ohms termination. Everyone
should be careful, it is *not* DC-decoupled and the output can be
destroyed when an external voltage is applied and the current is high
enough to melt the chips' internal clamping diodes!

All video outputs of the AV711x are constamt current outputs, so if two
75 ohms terminated video cables would be connected in parallel, the
video signal amplitude would decrease by 50%.

@Patrick: take a look here:
http://www.epanorama.net/links/videocircuits.html#distribution

Thomas




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