Within my profession, we use impedance bonds. One of the purposes of an impedance bond is to couple coded track circuit and CAB energy to the train rails. The coded audio frequency uses frequency multiplexing to carry transmit the audio signal down the rail to a reciever. Eight different frequencies are used and the boundaries of each track circuit is represented by these impedance bonds. Within each impedance bond are three tuned circuits; CAB, transmit and recieve. The CAB and the transmit tuned circuits are just a capacitor and inductor in parallel, however, the recieve tuned circuit has the capacitor, inductor and a resistor added. My question is the addition of the resistor there for antiresonance to prevent distructive current build up or to compensate for phase shifting as the signal moves down the rail?