Antitheft system

A system for preventing an equipment from theft, having:

• an internal combustion engine that is mounted on the equipment and is equipped with a generator that generates electric operating power when the engine is operated;
• a recoil starter that is installed on the engine to be manipulatable by an operator to operate the engine;
• an electronic key that is adapted to be carried by the operator of the equipment and stores authenticating data for identifying the operator who carries the electronic key;
• and
• an authenticator that is installed at the equipment and performs authentication check as to whether the electronic key is an authorized key using stored key-checking data, when the authenticating data is outputted from the electronic key;
• wherein the authenticator comprises a first electronic control unit having a first microcomputer, and the first electronic control unit conducts an initial check of only the first microcomputer and then performs the authentication check, when the electric operating power is supplied from the generator.