Could someone identify this?

[spark001uk]

Could someone put a name to this piece of equipment please, in the four foot? See them all the time at fishplated joints, sometimes with a box at both ends, sometimes only one end, different cable arrangements etc. Is it something to do with track circuit?
Thanks.

 

[hwl]

Could someone put a name to this piece of equipment please, in the four foot? See them all the time at fishplated joints, sometimes with a box at both ends, sometimes only one end, different cable arrangements etc. Is it something to do with track circuit?
Thanks.

View attachment 83229

Impedance bond between different track circuits ,the fishplates are part of Insulated block joints (IBJs) between track circuited areas.
In third rail areas the impedance bonds filter out the AC component of the current in the rails that is used for train detection while allowing the return DC traction current component to flow down the big aluminium strip between the different track circuit areas.

 

[spark001uk]

Ah OK thanks. What about the single ended ones, where the aluminum strip seemingly goes nowhere?

 

[TSG]

Ah OK thanks. What about the single ended ones, where the aluminum strip seemingly goes nowhere?

1) to parallel the path for the traction return current to rails on adjacent lines thus reducing resistance
2) as above but outside a substation to carry the return current into the substation
3) to transfer between a double rail track circuit (one through which the traction return current flows in both rails) and either a single rail track circuit (traction current flows in only one rail; typically used in S&C where resistance balance between the rails is not achievable), or a non track circuited area
4) a resonating bond, essentially to extend the length of a double rail track circuit.

Reasons 1 and 4 are often done together killing two birds with one stone

 

[ComUtoR]

Its a 'Spider'