The track circuit extends 3 km from the loop in each direction. At the loop
only the main line is track circuited the loop or No 2 road is 'dark'. When
an approaching train runs onto the track circuit the system waits 10
seconds to 'see' if an opposing move is present, if not the main line home
signal clears indicating that the points at both ends of the loop are
locked for the main line move and no other train is on the track circuit.
The home signal for the loop is in effect just a point indicator, it clears
whenever the points are set and locked reversed. A train departing the loop
will clear the arrival home for the opposite direction as soon as they key
out from no 2 track.
> It would seem a bizzarre situation if they both cleared at once.
> Also in the case of DICE how are the points and arrival signals
interlocked,ie
> what stops 2 drivers from issuing a conflicting set of instructions to
the
> same point motor, ie if both drivers inadvertantly try to drive both
trains
> into the loop road.
As far as I know DICE does not alter the basic ASW loop interlocking. This
means that while two trains cannot arrive simultaneously onto the main line
it is possible for this to happen in the loop. The ASW computer at the
train control centre is interlocked to prevent two trains getting a "key
loop" message for the same loop at the same time so one train would have to
be arrive into the incorrect road for this to happen.
> Also are the Radioed Instructions to the interlocking equip encrypted in
some
> way so as to prevent the operation of non intended actions.
> eg a train arriving at Gheringhap instructs the point motor to reverse to
the
> Loop Road , and due to anomolous propagation the instruction is also
received
> by the Interlocking equip at Wingeel Loop. (What happens)?
DICE operates by keying in a 3 digit code for each move. At Gheringhap
there is separate codes for arriving to the main, arriving to the loop and
departing from the loop for each gauge. Each gauge has a separate loop and
departing from the main requires no action as both ends of the loop have
self restoring points and, of course, the main is the normal position.
> Radio based safeworking is OK provided that the train is actually where
the
> safeworking system thinks it is,which requires an independant feedback
path
> for location verification, track ccts or axle counters provide this ,
could
> also be provided by GPS.
> I dont beleive the PTC ASW system has any independant locational
verification
> ability.
>
> cheers
> MD
>
>
-- Cheers Krel"Any sufficiently advanced technology is indistinguisable from magic" - Clarke's Law