Abstract: A head drum apparatus includes a head-affixing surface, a rotor transformer-affixing surface and a bearing-engaging surface which are all at the same height. This enhances the manufacturing accuracy of the head drum apparatus and a predetermined gap between the rotor transformer and assures that the stator transformer will be secured. In addition, the height of the head assembly in the course of setting it up is also secured. The head drum includes a lower drum rigidly affixed to a supporting plate of the head drum apparatus; a rotating shaft passing through the center of the lower drum and being rotatably engaged with upper and lower bearings; an upper drum, rigidly affixed to the rotating shaft, including the head-affixing surface, the rotor transformer-affixing surface, and the bearing-engaging surface which are all the same height and provided at the bottom surface of the upper drum; and a driving section disposed at the lower portion of the rotating shaft for driving the rotating shaft.

Abstract: An electronic lock and key includes an electronic key which produces a specific electric signal such as a frequency signal, photo signal or logic signal when inserted into the key holder of the lock; and an electronic lock which is comprised of a power source, a key holder, a lock signal generator, and a signal comparing circuit that compares the signal of said key and the signal of said lock signal generator.