I googled Passive anti-theft systems and this is what I got, thanks for the info !!!!!!!!!
What it is: Passive anti-theft systems (PATS), like Ford's patented SecuriLock system, protect against drive away theft through the use of an electronically coded ignition key. The system is designed to help prevent the engine from being started unless a coded key programmed to the vehicle is used. An indicator shows the system is working.
How it works: A miniature transponder with an integrated circuit and antenna is embedded in the ignition key. A wireless radio-frequency transmission transfers an electronic code between the transponder in the key and the vehicle. If the code matches, a code programmed in the vehicle, a signal is sent through the wiring system to the electronic engine control, allowing the engine to start. There are 72 million-billion possible codes, so every Ford sold worldwide for the next 10 billion years could have unique codes. New keys for replacements or spares can be purchased at dealerships. A customer may program spare keys to the vehicle themselves if they possess any two keys that operate the vehicle. A dealership technician may erase and program keys using diagnostic equipment. A maximum of eight keys may be installed in most systems.
Customer benefit: Increased protection against drive away vehicle theft, where the thief starts the engine and drives the vehicle away.
Ford status: Standard on most North American vehicles in model year 2000.