Abstract: A card reader adapted to receive a coded card is provided which includes an alternating current source and sensing means connected to the alternating current source. The sensing means includes a plurality of tuned circuits, each having a sensing coil. Each coil has a pressed powder ferromagnetic core and an annular pressed powder ferromagnetic sleeve encircling the coil in a plane parallel to the longitudinal axis of the core. The coded card consists of a thin electrically conductive layer having holes selectively formed in the layer in data positions, which, when taken together with portions of the remainder of the electrically conductive layer, constitute binary coded information. The card reader contains a protrusion which prohibits access to a portion of the card reader. A notch is formed in one side of the card to receive the card reader protrusion so that the card may be fully inserted into the card reader in only one position, thereby aligning the coils and the data positions.

Abstract: A unitary self-contained electronic combination lock is provided which includes a dead bolt manually operable from one side and operable from the other side only in response to insertion of a data combination card carrying a unique binary code in the form of selectively positioned metallic spots. Sensors located within the unit generate a binary 1 or 0 signal in response to the presence or absence of a metallic spot adjacent each sensor. The lock combination code is automatically changed to the data card's code upon insertion of a card having a code combination which includes part of the lock's code so that the previously issued cards will no longer operate to unlock the door. In this manner, the authorized code for each lock unit is automatically and independently changed to render inoperative all previously issued data cards.