Connect nodes as per the instruction. Since the coils on the two sides are disconnected hence the multimeter shows infinite resistance in this case. Connect pair of nodes from the same side for continuity testing. Check the multimeter's reading. Check the other side Complete the testing.. Check the circuit again. Ohh Wrong answer ! Thats correct answer Side A is the primary side with two coils a1a2 & a3a4. Side B is the secondary side with single coil b1b4 and tappings b2 at 86% and b3 at 50% of the coil. Connecting a2 and a3 provides series addition across a1 and a4, hence a2 and a3 are of opposite instantaneous polarity, while a1 and a3 have the same instantaneous polarity.Connecting a2 and b4 provides series addition across a1 and b1, hence a1 and b4 have the same polarity Thus, a1, a3 and b4 have the same instantaneous polarity and can be represented as dots. Also, a2, a4 and b1 have the same instantaneous polarity and are not dotted.