Murray loop bridge

Murray loop bridge is a bridge circuit used for locating faults in underground or underwater cables. It has been used for more than 100 years.

One end of the faulted cable is connected through a pair of resistors to the voltage source. Also a null detector is connected. The other end of the cable is shorted. The bridge is brought to balance by changing the values of R_B1 and R_B2, which is achieved when: