What is the purpose of Line trap and Coupling capacitors in carrier channels?

Line trap is an LC network inserted between the busbar and connection of coupling capacitors to the line and tuned to resonance at the high frequency and are used to confine the carrier currents to the protected section so as to avoid interference with or from adjacent carrier current channel.

Coupling capacitors is used to connect the high frequency (carrier) equipment to one of the line conductors and simultaneously serves to isolate the carrier equipment from high power line voltage.