With a few exceptions, smart light switches generally feature a neutral wire or neutral line. The purpose of this line is to provide power to the switch when the lights are turned off, something that becomes necessary when you add smart features. If there were no extra power, and the circuit was broken once the switch was flipped off, it would not be able to store information like WiFi logins, home security preferences, and other settings. This means you wouldn’t be able to integrate your light switches with your alarm system or smart speakers.;