The ignition switch, located on the steering column or in the dashboard, takes the power from the battery and directs it to all the accessories and electrical components of your car. It also transfers the power to the starter when you turn the ignition key.
An ignition switch has four positions which transforms into making a car to move:
OFF Or LOCK position; Turns off power to the engine and electrical accessories

ACC - Accessory position that provides power to electrical accessories only, not the engine.

RUN - The "ON" position that provides power to the engine and electrical accessories. The switch must be in this position for the engine to run and for the vehicle to be driven.

START - Used only to start the engine.....
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What's the possibility of converting a regular key ignition to a button ignition