Ok - the electronic cat flap is now live!
The cats "were passed under the sensor until it beeps 3 time" - which means that we now have 2 very unimpressed cats, but on the other hand they seem to be able to operate the catflap, so hopefully no more strange animals getting access t the house.
In addition the night-sensor mode is activated, so we basically have a cat-curfew in our house. The only problem with this is that the catflap does not have any kind of mode-memory, so if power goes off for any reason it will loose any memory of the night-mode.
So far so good.