Related Question
Equivalent resistance of the circuit,
Req = (12||18) + 8
Req = 7.2 + 8
Req = 15.2 ohm
Source current = current through 8 ohm resistor, I = Vr/R8
I = 20/8
I = 2.5 A
Supply votage V = I*Req
V = 2.5*15.2
V = 38 V
A wire pilot is generally economical for distances up to 5 or 10 miles, beyond which a carrier-current pilot usually becomes more economical.
In the cables, the location of fault is usually found out by comparing the capacitances of insulated conductors.