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Description 1, title of the invention
3. Detailed Description of the Invention The present invention seeks to provide a moisture
resistant, electrically stable microphone. FIG. 1 shows an example of the structure of a carbon
microphone widely used for transmission of a telephone. The carbon microphone utilizes the fact
that, when pressure is applied in a state where carbon powder is packed in a piston-like cylinder,
the contact area of the carbon powder increases and the resistance value decreases. In FIG. 1, the
carbon powder 5 is filled between the movable electrode 4 and the fixed electrode 7. 1 is a
protective plate, 2 is a moisture-proof film, 3 is a diaphragm, 6 is a lid, and 8 is a frame. When
this microphone is connected to the circuit shown in FIG. 2, before moving (4 vibrates by the
voice signal, the resistance value of the charcoal powder 5 changes, the current is regenerated,
and the potential at the 2jy 4a changes. By detecting this change, it functions as a transmitter.
When 9 in FIG. 2 is a microphone: 0 The greatest advantage of using such a carbon microphone
as a telephone transmitter is that the sensitivity is high. Moreover, the electrical impedance can
be reduced to allow more current to flow. On the other hand, the weak points of carbon and
other electronics are that they are weak to moisture and electrically unstable. That is, it is due to
the principle structure that the carbon powder 5 has hygroscopicity with respect to moisture,
and there is a defect that the resistance value is changed due to moisture absorption. In the
transmitter, the moisture-proof film 2 prevents the entry of moisture, but the structure is
complicated in one structure, and since the transmitter is in contact with the call port, a more
strict 1R resistance-proof structure is required. Also, as to the point of being electrically unstable,
the carbon powder 5 vibrates, strikes; Due to uneven distribution, the sensitivity and resistance
change, and the carbon powder is seized by EndPage: 13 Benif over electrode, and the sensitivity
is also the same. It means that resistance changes. Therefore, the present invention is intended to
provide a microphone which is resistant to moisture and electrically stable. The embodiments of
the present invention will be described below. The feature of the present invention is that a
piezoelectric magnetic transducer is used instead of the conventional carbon powder as an
acousto-electrical transducer, and one shown in FIG. 3 is one example thereof. . A case is
constituted by the frame 10 and the lid 11, and the printed circuit board 12 and the piezoelectric
magnetic transducer 13 are housed therein. The differential amplifier 14. A diode block 16 °
contact pieces 16 and 17 are provided.
A rubber washer 18 is attached to the frame 10, and the output lead 19 is inserted through the
washer and connected to the differential amplifier 14. A pair of resilient ring bodies 20.21 is
provided, and the piezoelectric magnetic transducer, sensor device 13 is a pair of ring bodies
20.21 \. , In favor of me. The piezoelectric magnetic transducer 13 is obtained by bonding a main
electromagnetic plate 23 to a metal plate 22+ as shown in FIGS. A ground electrode 24 is
provided on the back surface of the pressure electromagnetic two plate 23, and a pair of
electrodes 25 and 26 are provided on the front surface. Fig. 6a as a piezoelectric magnetic
transducer. b Fig. 7 a, b [showing can also be used. In the case shown in FIG. 6, the electrodes 28i
and 26 are provided on the front and back surfaces of the piezoelectric magnetic plate 23, and
there is no ground electrode. The one shown in FIG. 7 is one in which the electrode 26 shown in
FIG. 6 is partially exposed on the surface of the piezoelectric magnetic plate 23. Moreover, what
bonded two piezoelectric magnetic boards can also be used. The circuit of the differential
amplifier 14 and the diode block 15 is as shown in FIG. 4, and FETs 27 and 28 are used for the
differential amplifier 14. Since the output impedance of the piezoelectric magnetic transducer 13
(d is large, noise characteristics are improved by using an FET. The diode block 15 is for
removing noise (surge current of the line), and it is possible to use a diode or a zinc oxide
varistor. 29.30 in FIG. 4 is an output terminal. The advantages of using a piezoelectric ceramic
transducer in a microphone 6 are as follows. The point is that the output impedance is large from
the current (almost independent with rl, and even if the long connection m specific to the
telephone has high resistance, it does not introduce large loss. In addition, [iE electromagnetic
transducer transformer is intrinsically resistant to moisture, and is suitable for use in the
mouthpiece of a telephone, and no moisture-proof film such as a carbon microphone is required.
It becomes a thing. In connection with the point of this moisture resistance, nickel is used for the
electrodes of the piezoelectric ceramic plate or silver electrodes are used as shown in FIG. Also-.
Further, when configured as shown in FIG. 7, signals can be taken out from the same surface of
the piezoelectric ceramic plate. Further, as shown in FIG. 6, the divided electrodes 25 and 26 can
be used to take out signals from both ends thereof and to ground the metal plate 22 to reduce
As described above, according to the present invention, it is possible to obtain a microphone
which is resistant to moisture and electrically stable.
4. Brief description of the drawings. FIG. 1 is a cross-sectional view of a conventional
microphone, FIG. 2 is a circuit 1 of a circuit used for the microphone, and FIG. The figure is a
circuit diagram of a circuit used for the same microphone, FIGS. 5a, 5b, 6a, b, 7a, 7b are plan
views of piezoelectric magnetic transducers that can be used in the same microphone O It is a
side view. 13 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·
· · · · · · · · · · · printed circuit board, 14-· · · difference Dynamic amplifier, 16 ..... Diode block. Name
of agent Attorney Nakao et al. 1 person EndPage: 2 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 6 622 EndPage:
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