Is there any reason why one of the cheapo SCART switches such as you can get from Argos for a tenner cannot be used back to front, that is switching one input to two possible destinations?

SCART cables are wired bidirectionally - there are separate wires for audio in and audio out, and composite in and composite out (which implies the sync signal for RGB).

The switches that you mention usually only look at the audio/video in pins on the input sockets and transfer them to the audio/video out pins on the output sockets. They won't connect the in pins on the output socket to the out pins on the input sockets.

They also tend to have a record loop, which means some of the input sockets are interconnected in some way.

The only switch I've found which is a pure switch and switcehs all (relevant) pins indiscriminately, is the "rotary switch" from Satcure. Go to http://www.satcure.co.uk/accs/page4.htm and find product numebr 240-3646. I use this and it does indeed work perfectly in reverse. It lacks a record loop but that's actually to its advantage in a lot of cases as I've always noticed strange feedback issues with the cheapo switches. Also, it will do widescreen switching perfectly and there are no complications as to chooising RGB or composite - as I said, it's a pure switch which simply connects all pins on one side to the relevant pins on the other.

That's one of the ways they would normally be used so I don't see the problem?

Well, I was not saying that there is a problem, I was asking if there was because I do not know.

Apart from the Satcure recommendation, you and Chris seem to be giving me basically opposite answers, so I am not much better off.

I am not wanting to do anything complex. I just have a small security camera and I would like to be able to switch it from one TV to another. I do not even need sound switching as it doesn't have any.

See this thread http://www.digitalspy.co.uk/forums/s...d.php?t=538590 in particular post #7.

In that thread I think I suggested that the in/out thing may not be the actual cause of the problem but after thinking about it more I think it probably is. I think it might not matter if the switches connect together all 21 pins, but since they are designed for 3-in 1-out operation the cheapo switches probably don't do all 21 pins for operation in the other direction.

You could always buy one to try it, they are cheap after all! But my cheapo one definitely doesn't work in reverse, and the Satcure one does.

Basically, pin 19 on the In socket is connected to pin 20 on the Out socket (for example). If you connect it in reverse, pin 20 on the new In socket is connected to pin 19 on the Out socket - this won't work because it's the In pin on the Out socket that's connected - the TV will be receiving its input signel on its Out pin! It should work, however, if all pins are connected, i.e. 19 in sonnected to 20 and 20 is ocnnected to 19, but as I've mentioned the cheapo ones probably don't - in particular, the pins in the reverse direction are connected through to other input sockets to facilitate the record loop.

If all you want to do is switch the video signal (presumably it's composite video?) you could do it another way - by a 2-way phono switch usually intended for audio, or you can also get AV switches whjich switch both audio and video. These will be straight through connections, no complicated in/out wiring like SCART, so they will work either way.