B3 Impedance Bonds

[Archie]

Afternoon, would somebody be so kind to give me a basic in's and out's description of B3 impedance bonds function with regards to TI21's, and does anybody know the rail hole spacing's between 22mm holes that are drilled into the rail.

Any help would be much appreciated.

Many thanks

[PJW]

The basic function of any impedance bond is to separate the traction current from the track circuit current; the impedance bond is designed to offer a high impedance path to the higher frequencies used by the TI21 (around 2kHz) so that not too much track circuit current can flow through it, yet present a low resistance at the lower frequency (50Hz) used for traction return so that as much as possible can.
I do not know this specific bond and whether its use is on ac or dc electrified railway I am afraid so unable to answer your specific query.

Afternoon, would somebody be so kind to give me a basic in's and out's description of B3 impedance bonds function with regards to TI21's, and does anybody know the rail hole spacing's between 22mm holes that are drilled into the rail.

Any help would be much appreciated.

Many thanks