Re: Automated Level Crossings

Tintin (Tintinman@xtra.co.nz*fuck_off_spammers*)
13 Nov 1997 06:33:49 GMT

I'm of the understanding that the 25kvAC electrified section of the NZ
North Island Main Trunk uses frequency harmonics (?) to detect train
presence. A sender/receiver, a short distance apart, with a
current/frequency running through the tracks between them. If you're close
to them you can hear the high pitched whine/singing. I suspect it's similar
to ultrasonic detection of broken windows, where the breaking of the glass
changes the resonance of it. Then again, if you put your head to the tracks
and the train is real close, you can hear it through the tracks... hint:
DON'T try this at home...
Ben
-- 
(Hmmm... what would Lassie do?)




 A track cct is as you have summised, an insulated section of track where 
> the axles form a short across the tracks to actuate the cct, usually DC
but in 
> electrified areas AC , as the traction current cant be isolated .Im not
aware 
> in Australia of any other methods other track circuiting to actuate level


> crossings, other readers may know more.
> 
> MD
> 
> 
>