Electronic antitheft device using an electronic safety lock

Claim 1

An electronic antitheft device for preventing the unauthorized opening of a closeable member by the activation of an alarm and adapted to be energized from a power supply, said device comprising: a fixed circuit section contained within a lock mounted on said closeable member, and further comprising a keyhole, a plurality of electrical terminals placed along said keyhole, additional electrical terminals arranged on said keyhole and blocking means within said keyhole establishing a first and second positions along said keyhole; a movable circuit section contained on a key-shaped member capable of insertion within said keyhole and further comprising guide means for guiding the inserted key with relation to said blocking means into said first and said second positions, a plurality of electrical contacts arranged along the tongue portion of the key and designed to interconnect predetermined ones of said plurality of terminals when said key is in both said first and second positions, and additional electrical contacts arranged on the said tongue portion and designed to interconnect said additional terminals when said key is in said second position; and electronic circuit means further comprising code checking means which when energized by said power supply recognizes the presence of a member in said keyhole such that in response to the presence of a key containing said predetermined interconnections produces a switch signal and in response to any other member activates the alarm, and switch means having a first state for energizing said code checking means from the power supply and a second state for de-energizing said code checking means from the power supply, said switch means alternately changing state in response to successive switch signals; and wherein said additional contacts when interconnecting said additional terminals energize said code checking means from said power supply independently of said switch means, whereby when said key is inserted into said second position said device is placed in a pre-alarm condition and said closeable member is locked, and when said key is placed into said first poSition said device is disconnected and said closeable member is opened.