Strange that they don't use neutral fault devices. No, I've never seen such a beast, but it would be rather easy to design, I think.
If this is a 120-0-120V setup you'd need two voltmeters and a control circuit:
Voltages:
Hot1 - Neutral
Hot2 - Neutral
Hot1-Neutral should be in the 110-125V range
Hot2-Neutral -"-
Should any of the voltages fall outside the interval, the device cuts power to prevent damage from over/under voltage. (It would work on three phase too.) If the neutral comes loose and the load is unbalanced, the voltage will drift out of the allowed range causing the device to cut power.
BTW: What's wrong with the lights? Aren't they always red-yellow when switching from red to green? (Or is it just here?)
We have a traffic light indoors. (Ermmm, it had fallen down, you see... ) Logically the green wire is for the green light. (But for some reason, the red light has a brown wire)
[This message has been edited by C-H (edited 11-24-2002).]
