The SA boxes are sometimes hard to deal with and the ability to turn them on with a discrete command varies from area to area. Do a search in these forums for the various ways of possibly sending a discrete ON.

I ended up using a power sensing module, using a 12V transformer that was plugged into the back of the SA box. I think that I did so because the video sensing did not work for me, but my memory is hazy on that.

CJ