Electronic door lock using code number - has microprocessor with permanent memory storing emergency access code for use in case of loss of normal access number in live memory

摘要

The lock includes a keypad (2) with numbers allowing the composition of a code number to open the lock. When the correct code number is entered an electric latch (3) opens the door in response to a signal from electronic control circuitry. An indoor call bell (4) is intended to be included, and an audible warning (5) is provided to operate if a number is wrongly entered. The secret code number normally used for gaining access comprises four digits, the correct code being stored in a live memory. This enables the code number to be changed. The unit is powered by a battery charged from the mains, but in the case of mains failure the main live memory is lost. In this case a second emergency secret code number may be used. This is unchangeable and is stored in a permanent memory. If the normal number is erased, the circuit automatically changes over to the emergency number.