Speeding off in a stolen car, the thief thinks he has got a great catch. But he is in for an unwelcome surprise. The car is fitted with a remote immobilizer( 锁止器 ), and a radio signal from a control centre miles away will ensure that once the thief switches the engine off, he will not be able to start it again The idea goes like this. A control box fitted to the car contains a mini-cellphone, a micro-processor and memory, and a GPS( 全球定位系统 ) satellite positioning receiver. If the car is stolen, a coded cellphone signal will tell the control centre to block the vehicle's engine management system and prevent the engine being restarted. In the U. K, a set of technical fixes is already making life harder for car thieves. “The pattern vehicle crime has changed,” says Martyn Randall, a security expert. He says it would only take him a few minutes to teach a person how to steal a car, using a bare minimum of tools. But only if the car is more than 10 years old. Modern cars are far tougher to steal. as their engine management computer won't allow them start unless they receive a unique ID code beamed out by the ignition( 点火 ) key. In the U.K. , technologies this have helped achieve a 31% drop in vehicle-related crime since 1997. But determined criminals are still managing to find other ways to steal cars, often by getting hold of the owner's keys. And key theft is responsible for 40% of the thefts of vehicles fitted with a tracking system. If the car travels 100 metres without the driver confirming their ID, the system will send a signal to an operation centre that it has been stolen. The hundred metres minimum avoids false alarms due to inaccuracies in the GPS signal. Staff at the centre will then contact the owner to confirm that the car really is missing, and keep police informed of the vehicle’s movement via the car’s GPS unit.