Abstract: Disclosed is a method and apparatus for automatically limiting the amplitude output of a speaker for a mobile telephone when the telephone is in the active mode of operation. In a preferred embodiment, a tuned cavity in the stand-by mode operates in conjunction with the speaker to provide a higher than normal acoustic output. When the tuned cavity is moved away from the speaker, the acoustic output returns to the level equal to the speaker's normal output. In an electronic embodiment, a device switching the mobile telephone from the stand-by mode to the active mode also enables an amplitude limiter which limits the maximum acoustic output of the speaker to a level sufficient to prevent hearing discomfort or damage.

Abstract: Transducer circuitry, and an associated method, converts acoustic signals into electrical signals. The transducer circuitry includes a diaphragm which is positioned to receive acoustic signals, such as voice signals. Displacement of the diaphragm responsive to reception of the acoustic signals is detected by directing light energy towards the diaphragm and detecting characteristics of the light energy reflected off of the diaphragm. Changes in the characteristics of the light energy are determinative of the displacement of the diaphragm and, in turn, values of the acoustic signals received by the diaphragm. When embodied in a radiotelephonic device, the diaphragm can be positioned at a location best to detect voice signals generated by a user without the need to position electrical leads to extend to the diaphragm, or a winding positioned thereabout, to detect displacement of the diaphragm.

Abstract: A radiotelephone having a wave guide for channeling sound energy from a speaker to the ear of a person utilizing the radiotelephone. The wave guide is disposed adjacent the speaker and acts to direct sound energy from the speaker to the vicinity of a person's ear. The wave guide comprises an elongated wall structure having inlet and outlet end portions and a varying cross-sectional area that varies in a uniform and repeating manner between maximum and minimum values. This elongated wave guide with its varying cross-sectional areas forms an acoustical low-pass filter that efficiently transmits and propagates low frequencies, that is frequencies in the range of 300 Hz to 3,000 Hz.

Abstract: A radiotelephone having an acoustical wave guide for channeling and directing sound energy into a microphone forming a part of the radiotelephone. The wave guide includes an elongated tube structure that varies in cross-sectional area from an inlet end to an outlet end thereof. More particularly, the wave guide is formed by a wall structure that includes portions that assume a wave configuration. This wave configuration gives rise to the varying cross-sectional area that is repeatedly found between the inlet and outlet end portions of the wave guide. This wave type configuration for the wave guide forms an acoustical low-pass filter that propagates and transmits non-resonant low frequencies in the range of 300 Hz to 3,000 Hz.

Abstract: A pivotable flip element for use with hand-held radiophone units is specially configured to provide highly efficient coupling of acoustic energy into and out of the radiophone by virtue of an acoustic horn precisely formed as an interior cavity of the planar pivotable element. When arranged as a device for coupling acoustic energy into a microphone fixedly mounted to the radiophone housing, incident sound is directed from the horn mouth to its throat section, and thereafter through a rotary acoustic joint to an input channel to the microphone. The continuously rotatable rotary joint accommodates flip element rotations, allowing for the dualpurpose operations of protecting and covering the radiophone keyboard when not in use, and efficient input sound coupling when deployed.