Another one.

Cos apart from the Northern line problems, it's good system that works - why change something that works?!!

Indusi sounds suspiciously like AWS.

Q8: Magnetic trainstops would certainly be an interesting idea - it could be something like AWS is now.

Basically you put a largish electromagnet on the track next to the signal, in between a pair of rare earth magnets, and mount another electromagnet on the train. When the signal is green, the electromagnet is charged up to face in the same direction as the rare earth magnets (i.e. all three magnetic north poles point in the direction of travel). When the signal is red, the electromagnet could be charged up in reverse (i.e. N-S-N). The trainside electromagnet could simply be connected to some wizard circuitry that reads the electric pulses from the electromagnet, and if they match the N-S-N pole orientation, it opens the round-train circuit.

Using rare earth magnets would probably be expensive, given the huge number of trainstops currently in use, but it would have the advantage of being failsafe - if the power fails to the signalling system, you end up with a pair of magnets pointing north with a gap in between; the onboard train circuitry could read that as an N-S-N condition and stop the train.

So where's BAET to say how impossible this is... ;D

You can try it on the loksim simulator found on www.loksim3d.de

To delve further into details, the trackside magnet is actually not a permanent magnet, but is instead energized by induction from the train-borne magnet. Thus the name Induktive Zugsicherung, Inductive Train safe-working.

The net effect is, however, as Q8 describes -the magnets do not need any external power supply to work. In some variants, however, the switches that determine whether the trackside magnet is on or off are powered. Of course, they are set up in such a way that a power failure causes the magnet to activate, and thus give a speed restriction.

The Indusi systems gives you a braking curve that ends at the signal that is at danger -which is where you should stop, irregardless of yellows or whatever. Thus, since you can be sure of a train stopping where it should stop, you can have much smaller overlaps -"durchrutschstrecken". So, higher line capacity.

And while the driver has to follow certain parameters in their operation, they are free to act within those. So, if you are driving agressively, you can brake in such a manner that you reach your target speed exactly as it comes into effect. And if the signal should clear while you are approaching it, you can always use the Indusi Frei -button to bypass the Indusi sequence and raise your speed again.

Take a look at the link to a description of the Indusi system I posted upthread. It goes into a lot of detail and really does a good job of explaining how it works.

Right Igelkotten, I have now had time to study InDusi properly and have one question.

I can see the 1000Hz magnet is activated locally by the distant at caution, and the 2000Hz magnet is activated locally by the home at danger: what activates the 500Hz magnet and where from?

No I understand all that. But something has to open/close the switch to short-circuit the resonance circuit: the 500 Hz magnet is remote from a signal so what switches the short-circuiter?