Apparatus comprising a keypad and method of protecting keys against unwanted intrusions

摘要

A proposal is made to lock the keypad by depressing keys (10, 11, 12 . . . ). However, to avoid inappropriate use of the apparatus, a sequence of keys called secret key sequence is to be depressed for the apparatus to become operational. In an advantageous manner this sequence is determined by the PIN code contained in the SIM card (30). Application to cellular telephony mobiles.