Theft-prevention device for electronic audio appts., e.g. car radio - compares security codes representing product-specific value of electronic appts. and shuts down appts. when codes do not match

摘要

The theft prevention device includes a memory (SP) for storing a security code (SC1). The latter is compared with a second security code (SC2) and, when the two codes do not match, the electronic appts. is shut down. The first security code (SC1) represents a value specific to the electronic appts. when it is mfd. A control device (ST) in the electronic appts. reads the same product-specific value and uses it as a second security code (SC2) for comparison. The circuit for converting the product-specific value into the second security code is monolithically integrated with the control device in a circuit. The second security code cannot be read out via the connection lines of the integrated circuit. ADVANTAGE - Cannot be by-passed by exchanging memory or overwriting memory contents.