Abstract: A noise cancelling telephone transmitter comprising a cap and a cup coupled together so as to form an assembly insertable as a unit in the receptacle of a telephone handset. The cap is provided with an opening for passing sound. The inlet of the cap opening is covered by an acoustically deformable material such as a Mylar membrane. An electret microphone is mounted within the assembly such that the microphone acoustic entrance faces the outlet of the cap opening. A ring-shaped acoustic damping element is interposed between the cap underside and the plane of the microphone acoustic entrance. The cap is provided with a depending acoustic baffle which surrounds the damping element proximate the plane of the microphone acoustic entrance.

Abstract: A rocker switch is operated by the handset user to vary the impedance of a FET. The FET impedance varies in proportion to the duration of operation of the switch. The handset receiver "volume" increases or decreases in proportion to the FET impedance. An electret condensor microphone stabilizes the receiver supply voltage and provides improved transmitter linearity and low distortion.

Abstract: Anti-side tone transmitter insertable in a telephone handset improves transmission of the speaker's voice without distortion in high ambient noise environments. The transmitter cap is provided with a central opening in communication with an electret microphone. One or more satellite openings are spaced from and at least partially surround the central opening. An acoustic damping element is located below the satellite openings. The electret microphone is mounted below the cap on a PC board which contains the transmitter circuitry. The PC board is seated on a shelf formed in the interior surface of the side wall of the transmitter cup. Conventional telephone handset cord transmitter wires may be connected to screw terminals on the base of the transmitter cup or to spade lugs mounted on the PC board.

Abstract: A telephone amplifier for connection to a telephone set and a telephone handset associated therewith, the telephone set having a modular plug receptacle connected to a pair of receiver input signal lines and to a pair of transmitter input supply lines, the handset having a modular plug and cord connected thereto. The telephone amplifier includes a housing mountable on the telephone set. The housing has a modular plug receptacle for receiving the modular plug associated with the telephone handset. The amplifier includes an amplifier modular plug and a cord connected thereto. The amplifier modular plug is adapted for insertion into the modular plug receptacle in the telephone set. The amplifier further includes an amplifier operatively connected to the housing modular plug receptacle and to the amplifier modular plug and cord for amplifying a signal received on the pair of telephone set receiver input signal lines.

Abstract: An amplifier for a telephone handset provided with standard telephone line cord having a pair of receiver input signal lines for direct connection to the handset receiver terminals and a pair of transmitter input lines for direct connection to the handset transmitter terminals. A printed circuit board is electrically connected to and secured to the handset receiver. The receiver input signal lines are directly connected to the printed circuit board without alteration. The input signal is received independently of the receiver input signal line polarity. The transmitter input lines are connected directly to the transmitter without alteration.

Abstract: A rocker switch is operated by the handset user to vary the impedance of a FET. The FET impedance varies in proportion to the duration of operation of the switch. The handset receiver "volume" increases or decreases in proportion to the FET impedance. An electret condensor microphone stabilizes the receiver supply voltage and provides improved transmitter linearity and low distortion.