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About.com Health's Disease and Condition content is reviewed by Steven Gans, MD

Definition: A machine connected to car's ignition that checks for the presence of alcohol in the driver. The driver must blow into the machine to start the car and continue to periodically blow into the device to keep the car in motion. If the device senses alcohol, the car will not start or will turn itself off.

Not all states have ignition interlock laws. Some states require the devices after the first offense, while others require them only for repeat offenders. The offender is responsible for the cost of the installation and maintenance of the interlock device.

Also Known As: Interlock Device

Examples: After his drunk driving conviction, he had to pay to install an interlock device on his truck.