cut the flow of high voltage from the magnetos, stopping the combustion process in the cylinders. When such a "blip switch" was intermittently used on landing approach, this allowed a limited degree of engine speed control, as rotary engines generally did not have a conventional throttle in their carburettors to regulate engine speed, but only for governing the fuel-air ratio for start-up and full-speed operation. Anti-theft Kill switches are also used on land vehicles as an anti-theft system and as an emergency power off. Such devices are often placed in bait cars and configured so that observing police can trigger the switch remotely. This same idea can make the stolen object, such as a smartphone, useless to both the thief and whoever buys it, yet allow the true owner to reactivate it when/if it is recovered. Smartphones In smartphones, a kill switch is a security feature that allows the phone's owner to remotely render the smartphone inoperable if it is lost or stolen. From 2015 this feature is legally required in California for smartphones. There are also hardware kill switches on some phones, such as PinePhone, where the user can, by moving a hardware switch inside the phone, disable hardware like the camera, microphone, Wi-Fi or LTE. Software See also Brick (electronics) – an electronic device that can no longer function By analogy to physical kill switches, "kill switch" can be used to refer to a mechanism incorporated in software that can be activated by its manufacturer or licensor, for example if the product is withdrawn, or a maintenance fee has not been paid, or a device has been lost or stolen. It can also refer to kill switches for the stopping of malware such as in the WannaCry ransomware attack. Even to frustrate authorities by auditing the books for illegal facts. There is a debate about implementing kill switches in robots and advanced artificial intelligence systems. Industrial machinery On large industrial machines, an emergency stop button is typically located on the panel, and possibly in several other areas of the machine. Often, an emergency stop is made wireless using a remote control. This provides a rapid means to disconnect the energy source of the device to protect workers. For fail-safe operation, the emergency stop button is a normally closed switch, which ensures that a broken wire will not prevent it from being activated, but may accidentally activate the emergency