Repairing emissions equipment, this is not tailpipe testing. 
With this device a sample is taken of your exhuast as you drive down a highway, we are testing bigger trucks too. 
Later you recieve a letter to complete your registration.
Simple, this equipment is used more in other countries, not so much in the USA as the polotics want to keep the car testing garages open.
At least I dont have to wait in line for 20 minutes to have my car tested.