In electromechanical regulators, voltage regulation is easily accomplished by coiling the sensing wire to make an electromagnet. The magnetic field produced by the current attracts a moving ferrous core held back under spring tension . As voltage increases, so does the current, strengthening the magnetic field produced by the solenoid and pulling the core towards the field because direction of force of core will be in the direction of maximum inductance. The magnet is physically connected to a mechanical power switch, which opens as the magnet moves into the field. As voltage decreases because discharging of capacitor is done , so does the current, releasing spring tension or the weight of the core and causing it to retract. This closes the switch and allows the power to flow once more. Electromechanical regulators have also been used to regulate the voltage on AC power distribution lines. These regulators generally operate by selecting the appropriate tap on a transformer with multiple taps with the help of moving core. If the output voltage is too low, the tap changer switches connections to produce a higher voltage. If the output voltage is too high, the tap changer switches connections to produce a lower voltage. If the mechanical regulator design is sensitive to small voltage fluctuations, the motion of the solenoid core can be used to move a selector switch across a range of resistances or transformer windings to gradually step the output voltage up or down in autotransformers.