Post assembly process for adjusting the gain of an electret microphone within a communications apparatus
AssigneeNorthern Telecom Limited
InventorAndre J. Van Schyndel
Life of this patent
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Abstract
A post assembly process for enabling a manufacturer of acoustical communications apparatus, such as telephones and the like, to conveniently trim a sensitivity characteristic of an electret microphone therein, after assembly of the apparatus, whereby a uniform performance standard may be adhered to. When the acoustical sensitivity characteristic of the electret transducer is measured to be greater than a predetermined value, the transducer is exposed to X-ray radiation until the measured sensitivity characteristic has been reduced to the predetermined value.
Claims8
In a manufacturing environment of an acoustical communication apparatus, having an electroacoustics circuit with an electret microphone, a post assembly process for adjusting a gain characteristic of the electroacoustics circuit, the post assembly process comprising the steps of:
- a) energizing an individual one of the apparatus, in an OFF HOOK condition, via a communication line;
- b) operating a source of sound to generate a predetermined sound pressure level at a predetermined frequency within an operating frequency range of the electroacoustics circuit;
- c) via the communication line, determining sound amplitude of signals from the electret microphone;
- d) comparing the amplitude determined in step c) with a value being representative of a predetermined minimum amplitude and, if the amplitude determined in step c) is in excess of said value;
- e) operating a source of ionizing radiation to radiate at least a portion of the apparatus containing the electret microphone, until the sound amplitude is similar to the predetermined minimum amplitude, whereby the gain characteristic of the apparatus is adjusted.
In a manufacturing environment of telephone terminal apparatus, each apparatus including a transmit circuit having an electret microphone, a post assembly process for adjusting a gain characteristic of the electret microphone, the process comprising the steps of:
- a) energizing one of the telephone terminal apparatus, in an OFF HOOK condition, via a telephone line;
- b) operating a source of sound to generate a predetermined sound pressure level at a predetermined frequency within an operating voice band of the transmit circuit;
- c) via the telephone line, detecting an alternating current signal being of an amplitude in excess of a predetermined minimum amplitude, from the transmit circuit;
- d) radiating at least a portion of the telephone terminal apparatus containing the electret microphone, from a source of ionizing radiation, until the detected amplitude of the alternating current signal is similar to the predetermined minimum amplitude, whereby the gain characteristic of the electret microphone in combination with the transmit circuit in each assembled telephone terminal apparatus corresponds to a required standard.
Dependencies are inferred from the claim text.