Due to the electromagnet in the contactor, if power to the machine should fail the contactor will automatically disengage. Unlike machines with an ordinary latching switch (such as a common light switch), when the power is resumed the machine will not operate until being turned on again. As a result, magnetic starters often use momentary switches for "off" and "on" functions, as this type of switch returns to a defined normal position when released. Latching switches do not have this feature and therefore are normally not used with a magnetic starter.