Abstract: A ceiling-mounted loudspeaker includes upper and lower sound-directing structures having walls acting as a radial horn to provide a wide included angle of coverage for sound energy generated by a loudspeaker driver assembly having a piston for directing generated sound energy upwardly into the horn. The lower structure further has a continuously convex bottom configured and dimensioned to define a diffraction path for at least some of the sound energy exiting the output mouth of the radial horn, so that the convex bottom acts as a downwardly-directed diffractor. The radial horn and convex bottom together produce an oblate spheroid of sound energy affording a substantially uniform amplitude of sound within a large finite horizontal plane at the level of a listener.

Abstract: A normally closed reed relay switch is provided having an enhanced ratio of reclosure to open current. A permanent magnet is used to bias closed a normally open reed relay switch. An electrical coil is placed around one end of the reed relay switch so as to offset the flux distribution of the permanent magnet thereby allowing the switch to assume an open position. The position of the magnet and the coil with respect to the reed relay switch results in an enhanced ratio of reclosure to open current on the order of 10 to 1.

Abstract: A loudspeaker system which has a frequency response at any angle located about the speaker system which will be uniform such that the output sound pressure at any frequency from the speaker system will be as great or greater than the sound pressure from any other direction which comprises a reflected path from the speaker system. The speaker system includes a radial horn which radiates a spherical sector rotated 360.degree. through a horizontal plane is provided. One or two speakers are mounted so that they produce a pulsating cylindrical wave which feeds into the radiator and an inverted conical member is mounted in the transition portion between the pulsating cylinder and the output horn portion. This output is blended with similar wavefronts produced by a low fequency loudspeaker which is acoustically associated with a vented box. The vent is on the periphery of the box adjacent the low frequency loudspeaker and is narrower than the thickness of the walls of the box.

Abstract: An overload circuit for a loudspeaker system which indicates the overload and also automatically reduces the load on the speaker system to prevent damage in which a rectifier followed by a smoothing circuit is connected in parallel with the speaker and supplies an output to a magnetic coil for energizing a magnetic switch on overload so as to place a load dropping means in series with the speaker during overload. The load dropping means might be a lamp which visually indicates the overload condition.

Abstract: A wireless microphone and receiver in which the receiver output is muted whenever there is insufficient carrier present at the receiver to provide a clear noise free recovered audio or when there is radio frequency interference of a nature in strength to cause amplitude modulation on the IF envelope at the input to the FM detector. The invention places the receiver into a sampling mode whenever it is in a muted condition to conserve batteries and to provide a visual indication of such condition.