Dedicated Trackside Flux Sensor
As is widely known, 'flux' is the the rate of flow of energy or particles across a given surface. In this case the particles are trains, and the surface is the track. It is a sensor because it senses the flux, it is trackside because it is located by the side of the track, and it is dedicated a) because it works damn hard at what it does, and b) because it is not a multi-functioning device: it only has one primary role to fulfil, i.e. the sensing of flux, which triggers certain events.
Now, the Dedicated Trackside Flux Sensor, or DTFS, has a certain flux (or frequency of trains) programmed into it's little electronic brain - we'll call this the threshold flux. This shouldn't be confused with the maximum safe operating flux, which is a value of lesser importance, and is controlled by the PLC using 'blocks' within the layout of the amusement attraction. The threshold flux is a value above which the amusement attraction could be described as having a healthy throughput, or, to put it colloquially, "Whoa, this coaster is really eating up the queue, man!". This is undesirable, as it suggests that the amusement attraction has been well designed and has a high capacity - thoughts of this ilk would reduce the 'tweaking and optimising' contracts available to amusement attraction manufactures.
The job of the DTFS is therefore to detect when the flux of an amusement attraction exceeds this threshold value, and E-stop the ride. The process by which the ride is E-stopped is actually quite interesting: rather than just flagging up a 'DTFS'-style error on the operator's console, the device actually mimics one of many other possible faults, such as an over-speed train, an occupied block, or an over-weight train. This generates extra revenue for the amusement attraction operators, who in addition to 'tweaking and optimising' can now create additional contracts with the amusement attraction operator, in this case Alton Towers Resort Operations Ltd.
With this in mind, it is clear to see that a quote such as " Apparently the rides dedicated trackside flux sensors failed...people are still queuing!" nicely demonstrates the main concept behind the DTFS. Had the DTFS been operating correctly on this ride, it would have been out of action much earlier in the day, resulting in the queue having to be emptied and closed off (hence failed DTFS = people still queueing).
As a side note, it has been heard from the grapevine that Intamin have indeed been having many problems with Thirteen's DTFSs. For the first couple of weeks in operation, Thirteen's throughput was shockingly high, indicative only of a poorly running DTFS system. Things then perked up, but subsequently the system has only been half-operational, with triggered sensors only reducing the capacity of the ride, rather than fully ceasing it's operation.
Activation
There have been many rumours about how to activate the fabled dedicated trackside flux sensors. However, the only confirmed method is for a bolt of lightning to strike Thirteen's crypt at precisely 10:04pm, thus giving one of the trains the required 1.21 gigawatts of power allowing the train to accelerate to 88mph. At this point, the dedicated trackside flux sensor will kick in and the train will be warped 9 years into the past, where riders can give John Wardley a bloody good talking to and prevent Air and Colossus from ever happening.
