Carrier-current line trap for power lines

CARRIER-CURRENT line traps first were proposed about 1928 as a means of reducing carrier-current signal dissipation over undesired lines of power systems. Their use for this purpose has increased steadily with the increasing complexity of the power-line circuits upon which carrier is used. That line traps have done an effective job is attested by the fact that carrier systems are functioning more economically and more reliably with the use of steadily decreasing transmitter powers.