32 fig2 and brings bolt 20 along with it so that the bolt is retracted from its extended locking position as nut 40 begins its inward travel along drive screw 70 toward motor 80 cam follower arm 44 is deflected along cam lip intermediate edge 94 to cam lip trailing edge 93 thereby rotating nut 40 counterclockwise so that locking arm 42 moves out of slot 28 on bolt 20 to terminate the dead bolting function as best shown in fig1 and 11 as bolt 20 is retracted it compresses back spring 68 which is positioned concentrically surrounding drive screw 70 and in between motor 80 and bolt inner edge 24 back spring 68 is centered on drive screw 70 by spring bushing 60 which has a flange 62 contacting bolt inner edge 24 and a hub portion 66 supporting back spring leading edge 67 the compression of back spring 68 gradually increases the load on motor 80 as the bolt 20 is retracted thereby slowing down the revolution of motor 80 as bolt 20 approaches its fully retracted position operation of motor 80 to cause nut 40 to move along drive screw 70 toward motor 80 is initiated upon entry of a predetermined combination via electronic code input means 300 shown in fig1.