point of said power switch and said first diode and said ground side output line, said series circuit comprising a second diode and a load resistor with a direction from said internal power source and said ground side output line to said positive side output line being a forward direction; and means for switching a drive power source driven by an external power source from an external apparatus when in a plug-in power.
In a further embodiment, the power switch is removed from the above-described embodiment, and the internal power source and the plug-in power from the external apparatus are automatically switched.
With the constitution described above, the internal battery and the external power source (plug-in power) can be used in common.
Even if the internal battery and the external power source are used in common as described above, the power switching can be automatically carried out. Therefore, no burden in operation such as switching is imposed on a user as in prior art, and no interruption of absorption of sound occurs as power switching takes place. In this case, generally, the internal battery is higher in voltage than the external power source so that the power switching is carried out first from the external power source, thus preventing wasteful consumption of the battery.
Further, since the power switch is provided on the microphone body, the switch operation can be done at hand. When the power is off, the output line of the voice signal is grounded in an AC manner. Therefore, on the apparatus side to which the microphone is connected, its input is short-circuited in an AC manner, and even if the volume is increased, no noise occurs.
The power switch may be of a 2-contact switching system, which is small and inexpensive. Accordingly, it is possible to further miniaturize the microphone itself, reducing the cost. As the case may be, even if the power switch is omitted, the internal battery and the external power source can be automatically switched.
The present invention relates to a power circuit for a condenser microphone capable of supplying an operating power from either internal power source (mounted power source) or external power source to a microphone unit.
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Pages: 1 2 Social tagging: circuit > Condenser > Microphone > Power
