Added security--and product differentiation--are provided by an electronic-ignition-key system on the new CLK coupe from Mercedes-Benz. Integrated into the remote locking unit, the electronic key has a half-inch snout on one end, which slips into the ignition lock. As the driver begins to turn the key, the car sends an infrared signal "asking" for the password. For added security, the system changes passwords each time the car is started. As backup, the remote locking unit includes a small conventional key for opening the door. Failure of the remote unit's battery does not affect the starting of the coupe (the password process does not use the remote's battery).