What is this and what do the letters stand for please?

[Islineclear3_1]

 

[rd749249]

TPWS grids for over speed sensor (OSS). One is the arm, one is the trigger. The arm will come first, the trigger second based on speed passed over. Emergency brake applied and tea and biscuits with the manager.

 

[haddock1000]

Railway signalling engineer here.

I believe this is an enclosure for TPWS (Train Protection and Warning System) equipment.

OSS stands for Over Speed Sensor, the OSS grids are the two which are spaced a little ways apart on the approach to the signal.

Trig/Arm stands for Trigger/Arm. Basically the first grid the train passes over on the approach is the arming grid (transmitting the arming frequency), the second grid being the trigger grid (transmitting the trigger frequency). If the train sees the trigger frequency within a (nominal) 1 second after the arming frequency is seen, the emergency brakes are applied

I think 36/37 and (1) refers to the identification of the location of the asset (maybe the signal no. that it is protecting?). I’d need the location to say any more.

 

[Islineclear3_1]

Thanks guys

The location is Littlehampton, so 36/37 refers to the signals. I hadn't realised that TPWS applies to mechanical shunt signals

 

[haddock1000]

Yes, as it is a subsidiary to signal 36 - If signal 37 were off you would want to stop transmitting the TPWS signal so the emergency brakes don’t come on.

 

[Islineclear3_1]

Cheers, every day's a school day

 

[jamesst]

TPWS grids for over speed sensor (OSS). One is the arm, one is the trigger. The arm will come first, the trigger second based on speed passed over. Emergency brake applied and tea and biscuits with the manager.

Haha there wouldn't be biscuits for that at my Toc!!!

 

[pdeaves]

What is inside the physical box in the picture? I would expect it to be, effectively, a 'junction box' for the TPWS cables, with the actual technical gubbins in a location case further away.

 

[WAO]

Pity such equipment doesn't have an enclosure suitable for outdoors - especially where there's sea spray.
WAO

 

[haddock1000]

I believe that it is just a termination point for joining cables, yes. The actual equipment are red yellow and green boxes that are the same size and mount onto the same plug boards as BR930 series relays (see the first image here for a photo - on mobile so can’t get the direct link to the image). Usually the modules are in the same location cases as other pieces of signalling equipment related to the same signal.