Abstract: A decoder is provided for disk tumble locks which is electrically rather than mechanically operated. A plurality of separate keys each has a blade sufficiently long to extend through all of the disks in the lock. At least one cut is provided in the blade of each key. The depth of the cut in each key is different, the cut of each key being coordinated to a different depth of disk from among the known alternative disk depths for the given tuumbler lock to be decoded. The base surface of each cut contains discrete electrical contact connected by a discrete conductor to a point on the key which is externally accessible when the key is fully inserted into the lock. Each contact is positioned on its key so that, when the key is inserted into the lock keyway, an electrically conductive circuit is completed by the disk if the depth of the disk corresponds to or exceeds the depth of the cut.