| 摘要 |
A microphone which uses noise-adaptive automatic output level control in speech recording. An input amplifier cooperates with a voltage doubler to form an automatic gain control. A diode and capacitor circuit provides for envelope detection of the signal which is then differentiated, amplified and detected to result in a DC control signal. This control signal is applied to an output amplifier which functions as a three pole Chebyshev filter in which a reduction of gain dampens one pole of the filter causing the response to drop off, so that the signal appearing at the output of the microphone has a substantially high speech-to-noise ratio. The output signal appears at a constant level where it may then be acted upon by the automatic gain control of an associated tape recorder connected to the microphone.
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