The Dahlander circuit uses a special circuit to switch between a slower speed (circuit in a delta) and a fast speed (circuit in a double star). At a low speed, the circuit looks like a triangle and at a high speed like a double star, which is why it is also called a delta-double-star circuit. The speed is switched via the pole change in a ratio of 2:1. With pole-changing motors, the delta connection is made via the wiring of the mains connections (L1, L2, and L3). The double star connection is achieved by bridging 1U, 1V, 1W, and via the mains connections (L1, L2, L3) to the terminals 2U, 2V, and 2W.