I have got it working
HUGE thanks to greencounty who made it possible and his circuitry is very clever and simple.
Thanks to him when the engine is running or Accessories are on
1)reverse camera comes on when reverse gear is selected
2) the front camera can be selected at any time
3) the rear camera can be selected at any time (even though you are not in reverse)
4) no camera is powered when you don't want it on
5) no extra harnesses were needed to be purchased
6) only one switch is used
You need to know that it requires
A) cameras that will operate on +6V but they are plentiful and that is the way the Fujitsu-10 h/u is set up.
B) one oe wire to be cut
c) one oe wire to be spliced
I'm not quite finished yet. I must have a poor connection somewhere as occasionally I get monochrome pictures with jaggies. When fixed I will be posting a Guide for Dummies. If I can do it then anyone can!