RE: KAT5 Specifications

["Keith Doxey" <keith.doxey@xxxxxxx>]

There was I thinking that posting the design document would stop the
questions !

Why SCART ?

1. Most modern TV's have 2 SCARTS
AV1 is usually Composite/RGB
AV2 is usually Composite/S-Video

2. Very few people have ALL their AV Kit as S-Video. In my case I have a PC
and a DVD player that are S-Video capable but all my satellite receivers
and
videos only have Composite out (except Digibox which has RGB but not
currently used).

3. As mentioned by others, almost all domestic AV kit is SCART but only
some
models have phonos and S-Video.

4 Using SCART enables me to use the same box and cutouts for all models in
the range and also allows the same PCB to be used for composite and S-Video
options. The prototypes shown to the "Churchill Arms 6" had 4
phonos and a
minidin but it didnt fit the box properly.

5 When the switcher is available it will be possible to connect both
S-Video
and Composite sources to it. By using SCART on the reciever means that the
same input on the TV can be used for whatever source you select. Most S
enabled TV's allow you to toggle between Composite/S with a single button
press. If you get the wrong selection you simply get a black & white
picture
and you know you have the wrong setting. My Mitsubishi TV only has an
S-Video connector on the front mounted AV3 input along with L,R,V phono's
(although SCART AV2 is S enabled). It will not allow you to select between
S/Composite, the action of inserting the minidin forces the S video mode.
To
feed a composite source into it you would have to change the leads over.

TROUBLE WITH SCART.

The main cause of trouble with SCART is the size of the plug and the weight
of the cable. This can cause the plug to partially come out of the socket.
Providing some form of strain relief (cable tie round the TV stand to take
the weight) will solve that. It is good wiring/cabling practice to not let
the connector take the weight of the cable. Also keeping the cable neatly
routed and tidy helps the WAF, especially considering the number of cable
we
tend to have on a typical AV setup  :-)

The only other common fault with SCART is broken joints on the PCB in the
TV/Video. Again this is related to the problem of strain on the connector
and the fact that the flow soldering processes used in mass production do
not give a very strong solder joint on the socket. Mine will be
mechanically
secure and hand soldered which will stop those problems. As stated before
you are free to use whatever you wish for the equipment end as most
configurations are catered for with ready made and easily available leads.

BIG ADVANTAGE OF SCART.

SCART has one big advantage over separate phono/BNC/Minidin connectors and
that is the ability to select the input via Pin 8. The Americans have to
mess about with IR signals to select and AV input, we just need a voltage
on
1 or 2 pins to select either Composite or RGB input. We even have the
ability to select 4:3/16:9 mode on later TV's. Sadly when the spec was
updated to allow S-Video input and Widescreen options they didnt come up
with an auto-switching option to tell the TV it was S-Video not composite.

Right.....back to the layout design.

Keith


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