A locating system for sport objects where the user carries an r.f. transmitter, and the sport object has a conductive stripe thereon which increases the load on the transmitter as it moves closer to the sport object. The conductive stripe has an effective length of one-quarter wavelengths at the signal frequency to act as a tuned antenna.

A game court boundary indicator system in which critical zones adjoining the boundary lines have protected and/or concealed sensing means responsive to the proximity of a playing ball having triggering means, said sensing means being unaffected by the presence of the player's body or the tennis racket, and connected to circuit means actuating indicating means.

A self contained electromagnetically resonant device includes a resonant circuit assembly encapsulated in an elastomeric material surrounded by a rigid casing. The resonant circuit includes an elongated core of sintered magnetically soft material and a coil connected across a capacitor which is spaced from the core. The elastomeric filler co-acts with the casing to substantially retain the core in its original form and dimension in the event of core breakage to maintain the resonant frequency and quality of the resonant circuit assembly. The device is resonantly excited solely by exposure to an electromagnetic or magnetic field having a suitable frequency component.

The present invention performs improvement in travelling characteristics of magnetic tapes and scanning chracteristics of magnetic heads by forming a tape running face which is made to run along a part of a course of a magnetic tape bent by a magnetic head to support the magnetic tape ranging over the full width, an opening which is located in the tape running face and made to run along an area of movement the magnetic head, and guide members for guiding the both edges of the magnetic tape to the both sides of the tape running face.

This invention relates to an electronic golf ball comprising a central resilient sphere, a mass of elastic material surrounding the sphere and an outer casing, the central sphere including an electric squegging oscillator circuit, a battery therefor and a transmitting coil, all enclosed in a spherical mass of a set resin which forms a solid core, the spherical mass being located with close fit in a hollow spherical cavity formed in the central resilient sphere. The battery is a mercury cell located within the transmitting coil, as are the other components of the squegging oscillator circuit. The electrical circuit may include components which permit the oscillator to be turned on and off when the golf ball is brought into and then moved out of an A.C. magnetic field having a predetermined frequency.