Functional

• Alcohol sensor accepts breath sample as input (critical)
• Sensor obtains digital reading of BAC (critical)
• If the BAC is greater than 0.08%:
• Disable starting the car (via Bluetooth) (critical)
• Send SMS message containing driver's location to emergency contacts (via Bluetooth) (non-critical)
• Otherwise, allow driver to start the car (critical)

• Reliability
• Disable car start once test has failed (critical)
• Portability
• Size no bigger than a normal car keychain (non-critical)
• Timing
• Provide a response in no more than 5 seconds (critical)
• Performance
• Driver can try multiple times until he passes the test (non-critical)

1. 1. User turns on device. A yellow LED will turn on signifying that the device is starting up. When the device is ready for the user's input, a blue LED will turn on.
2. 2. User breathes into the device for a few seconds, meanwhile the yellow LED is on, signifying that it's processing the user's input.
3. 3. A green LED will turn on when the user passes the test (the user's BAC is below 0.08). A red LED will turn on when the user fails the test.
4. 4. If the user passes the test, the user will be able to start the car, as long as the green LED is on. Once the car is started, the user can turn off the device.
5. 5. If the user fails the test, the user will not be able to start the car. To retry the test, the user must turn off and then turn on the device, and repeat steps 1-3.