BUT: Since a few days I can't charge any of them. The LED's on the dock stations wan't go on; the Pronto's wan't get charged.
I don't know why this has happened. As far as I know nothing has changed. I could understand a faulty Pronto or a faulty dock station, but not all three Pronto's and/or all two dock stations.

I used the chargers at different circuits. I reset the Pronto's - and can't reset them anymore because the battery level is too low. I checked all connections. I tried an unused battery back in one of the Pronto's.
Nothing helped.

What can I do?
I would very much appreciate if someone could help!

I would agree that the chances of both docks going faulty at the same time is slim.... Unless of course on of the Prontos is faulty and has shorted both docks. However, I would also check the voltage out from the little wallwart transformers. You may have had a mains issue that happened to have knocked out both.

I tried another adapter (12V 400mA). It didn't help.

Accidentally I have ordered another RU990 with a dock, which I will get within a week. I think I will try that one alone, to see if that works. If so, I will try one of my older Pronto's on the new dock, if that works, go over to the other two. If it doesn't I will go back to the new RU990 and see if it is still okay. And so on.

A main issue in two circuits has a very low probability. (And the circuits are protected.)

Probably I did something stupid. But what? I don't know.
USB works fine, by the way.

Anyway I will come back here and let you know.

Also, how did the batteries stand up - please see my post regarding the poor use times (battery bars / battery life)

As far as I know there was nothing wrong with the 3 ! batteries. The loaded and charged well.

I made the first steps. Read a lot of postings.
Bought a thorax screw driver, opened the charger and am amazed about how small the fuse is.
So let's see where I can buy one (in or near my hometown first).

By the way I got another DS (with a RU 990) and I could load my other RU990 / TSU7500 with it, too, without any problems.

So I have two faulty DS and it could be the fuse. But what could have caused it ?? - at the moment a theoretical question.

The person who dit it told me that it is not uncommon with these Philips' DS that after some time they stop working.

Thanks for your reactions.

I was thinking, I've got a boxful of Conrad RF switched power sockets, and I wonder if these are the ones for which there seem to be hex codes available?
They don't suffer from the too-close-for-comfort (interact < 1m) syndrom like the Intertechno's and work pretty good (currently for my room lights).

They're Conrad # 646452:
[Link: conrad.de]

Sorry that I didn't react sooner, but I hadn't seen your answer before.

Anyway, I don't know if there are hex codes available for those Conrad RF switched power sockets. Probably you know more meanwhile.