I have noticed what appear to be orange metal rectangular shaped covers or boxes fastened to railroad ties in the Chicago area. They are sometimes mounted in pairs about 7 or 8 ties apart. Can anyone tell me what they are used for?
These are probably induction coils. They are located at the POWER GAPS. You are undoubtedly looking at an electrically powered line that also uses cab signals.
On an electric railroad you have a power source, third rail or overhead wire, but need a return path which is the rail. Examine the rails. you will find heavy power bonds at certain locations and lighter weight bonds on the other rail. But at a gap you have to have, well a gap. The induction coil bridges the high frequency signal signal across the gap while allowing the lower frequency (DC signals) to be broken at the Insulated Joint.
NYCT does not have induction coils: It does not have cab signals. LIRR does have these induction coils because it does have cab signals.
Leastwise this is what I think you are looking at, and my understanding of how it works. But, LIONS are covered with fur and so might not have all of his facts exactly right.
ROAR
Another possibility is that these are remote control “pucks”, which are commonly found on non-electric railroads which use remote control locos for switching. These are transponders placed between the rails nearing the end of a remote control zone which automatically cause the remote control loco to prgressively reduce speed and eventually stop before the end of the zone (sometimes called “pull back and stop protection”).
It would be helpful if you specified which line and where you found these boxes. There are a number of carriers in the Chicago area and they don’t all use all the same technologies.
Size of those boxes ? (approximate guess is good enough - don’t want you trespassing to measure them !)
Sometimes also referred to as “impedance bonds”. See -
http://www.twincomfg.com/Impedance_Bonds/Twinco_ImpedanceBonds.htm
and
http://en.wikipedia.org/wiki/Track_circuit
- Paul North.
I would guess the boxes were 8 to 10 inches long by 4 to 5 inches wide. There were no electrical connections visible. These boxes were not on an electrified railroad.
The location was going into Chicago on an Amtrak train from Indianapolis and we had passed a container yard going into Chicago.
If that’s so, they are almost certainly remote control “pucks” as described in my earlier note.