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Re: 42220

On Wed, 22 Sep 1999 15:10:50 +1000, "Chris Stratton"
<stratton.chris.cp@nospam.bhp.com.au> wrote:

>Roderick Smith <rodsmith@werple.net.au> wrote in message
>01bf04a1$9f1284e0$232d11cb@rodsmith">news:01bf04a1$9f1284e0$232d11cb@rodsmith...
>> AFAIK all 81s and all NRs.
>> Probably all Gs, BLs and 82s too.
>> Possibly more (stuff for Westrail?).
>>
>> 81s had troubles in the long tunnel on the Ulan line, as the system relied
>> on a reading of true speed from looking at the ballast: no light, and no
>> ballast.
>>
>I thought it was some type of radar, not optical based. Otherwise it
>wouldn't work at night either would it?
I can confirm this it is doppler radar the most common failure of this
device is the screen being coated with dirt a simple case of getting
under and giving the screen a good wipe over with a sweaty !
PS this device can see in the dark
PPS what stuffs it up is bridges like the Wagga viaduct with gaps
between the sleepers!
regards Paul Johnston (mnrc)