Want to see even older detector technology? This video clip [www.youtube.com] is from a series of presentations from the British Transport Films archive titled "The New Tradition" from 1968. It shows a Servo hot box detector connected to a paper "Servograph" system. I am sure this pre-dates any digital numeric readout system. Here is a link to a Pensy graph detector of nearly the same idea. [kc.pennsyrr.com]


While the US, Canada, Mexico, and I believe but have yet to confirm Australia, are the only places I know hotbox detector transmit spoken digitized voices via radio, all the other ones I have seen and read about send their data back to a central traffic control center (dispatcher) who then contacts the train via radio or telephone. Traveling abroad, I have accidentally stumbled across hot box detector installation sites while going out to railfan. Additionally, I have never seen in person or on the net dragging equipment detectors, again, in places other than North America.

Here are a few links to some videos of detector sites I stumbled upon while traveling abroad. [www.youtube.com] (Sweden)
and [www.youtube.com] (France)

According to contacts of mine who both work for SNCF (France) and SJ (Sweden) if a passing train trips the detector, they generally receive the information from the dispatcher within 90 seconds or so. Not too bad, but compared to here train crews (I think) hear the alert tone from the detector almost immediately after a defect is detected allowing the crew to power down and begin braking. Seems like a little better idea than traveling another mile or more without knowing.

Also, out in the desert near Kelso CA, there is a similar looking device mounted on the outside of the rails called a Hot wheel detector. I asked a train crew what this device was used for and was told that it is used to detect stuck brakes. However the one in Kelso is used to detect brakes that are not functioning. The train crew I talked with mentioned that as the trains descend the hill at Cima headed west to Kelso ALL of the wheels should be significantly hotter than the ambient temperature. Thus, if the detector detects a wheel that is not 'warm' it sends a message to the carmen at Barstow (from what I was told) to inspect that car before the train descends Cajon.

Along those lines, out driving in the Swedish countryside I stopped at a detector location near Horndal. The Swedes use a little different way to detect stuck brakes. Instead of the side-of-rail mounted detector, they have the detector installed inside a bungalow with a long pipe extending to the side of the rail with a piece of rubber tubing at the end to allow for ice to hit the pipe without damage. [funpage.home.comcast.net] Here you can see the normal hot box detector with the usual ramps and induction flange detectors to the left and stuck brake detector pipe to the right.