A telephone hanset is made with two elongate molded parts, a back part and a front part. The back part is arcuate in side view and is substantially rigid. The front part has a substantially flat central portion which is flexible, with a housing at each end for the transmitter and receiver. The two parts are assembled by flexing the front part to conform to the back part, the two parts being connected together. This avoids the need for complex molds for molding the front part as no re-entrant walls occur for the housings.
In a telephone handset having an elongate housing which defines a cavity, wherein a microphone and a loudspeaker are arranged, the microphone is arranged air-tightly in a chamber of the housing by a flexible gasket. A portion of the gasket extends at least partially over the rear part of the microphone. In order to hold the microphone and the gasket under weak pressure and vibration-free in the chamber, a separate plate engages this portion. A printed circuit board arranged in the cavity can be used for this purpose. The loudspeaker can be mounted in a corresponding manner.
A telephone handset comprises elongated complementary upper and lower housing members that mate at their perimeters to form a hollow handset housing. The lower housing member includes a pair of spaced apart transducer receiving cavities, each being shaped to receive a cylindrical transducer surrounded by a flexible tubular gasket and form an acoustic seal therewith. Each gasket includes flanges around its circumference that project radially outward and in a direction opposite to the direction of insertion of the transducer/gasket assembly into its associated cavity. Such construction provides adequate mechanical retention between the transducer and the lower housing member and avoids the need for additional retaining hardware. The upper housing is joined to the lower housing using one or more pairs of side-mounted, interlocking hooks and latches. The upper housing further includes ribs, molded therein and positioned to maintain the transducers in place when it is joined with the lower housing.
An improved noise cancelling apparatus is disclosed combining a unique directional noise cancelling microphone structure with a noise reducing, signal shaping electronic circuit. The microphone structure simultaneously receives two input signals; a first signal containing only ambient noise and a second signal containing both ambient noise and a voice signal. The microphone structure cancels the two noise components and transmits the voice signal into an electrical signal. The electronic circuit further processes the electrical signal to suppress any noise components not cancelled by the microphone structure. The electronic circuit also functions to enhance the high frequency components of the voice signal to provide a richer, more pleasant sounding output. Because the unique microphone structure is combined with the electronic circuit the noise cancelling apparatus of the present invention provides a cleaner, more pleasant sounding output than that of the prior art.
A telephone handset for use in noisy locations has a noise cancelling electret transmitter which receives a normal acoustic input at the front end and a background noise acoustic input to the rear end. The input to the rear end is via a grill on the back side of the handset. A dielectric shield is positioned between the grill and the transmitter. A resistor is inserted in series with the transmitter to reduce the sensitivity and produce a lower than normal transmit level. Also, a filter is used to reduce the level of high frequency emphasis.
