The Tennessee Department of Safety & Homeland Security Ignition Interlock Program rules definition is:
Ignition Interlock Device - a device which connects a motor vehicle ignition system to a breath-alcohol analyzer and prevents a motor vehicle ignition from starting if a driver’s blood alcohol level exceeds the calibrated setting on the device.
In other words, an ignition interlock is an alcohol detection device that is installed on a motor vehicle and analyzes breath samples of the driver. The device prevents an alcohol-impaired person from starting the vehicle and requires random retests be submitted while the vehicle’s engine is running. In Tennessee, all ignition interlock devices must include a camera.