The present invention relates to a handset microphone that is free of noise contamination during a switching operation and malfunction due to an external magnetic field.
Various types of microphones are known that acquire and output sound. One of the types is called a handset microphone, which can transmit speech when a transmission switch is turned on and cannot transmit speech when the transmission switch is turned off (see Japanese Patent No. 3857591). The transmission switch of a handset microphone is generally implemented by, for example, a push switch. The push switch of the handset microphone is continued to be pressed during speech transmission. The push switch is returned to the original state (i.e., not pressed) to stop speech transmission. The contact of the push switch is mechanically opened or closed.
Mechanical turning on/off operation of the contact of the switch readily generates noise. In order to prevent such noise contamination, mechanical contact may be replaced with a reed switch openable or closable by the movement of a magnet attached to a switch knob.
Use of a reed switch as an operation switch of a handset microphone can prevent noise caused at a start or stop operation of speech transmission. A reed switch having contact operated by a magnetic field may however malfunction in an unintentional magnetic field from the exterior.
Handset microphones are often used for radio communication machines and usually transmit radio waves in cooperation with switch operations. In such a radio communication machine, a malfunction of the switch in the handset microphone is caused by an external magnetic field and then leads to undesirable transmission of radio waves.
It is an object of the present invention to provide a handset microphone that is free of noise contamination during a switching operation and malfunction due to an external magnetic field.
According to an aspect of the present invention, a handset microphone includes a microphone unit, a first switch for turning on or off the output from the microphone unit, and a second switch for enabling or disabling the output from the microphone unit; the first and second switches have contacts operated by a magnetic field; the contact of the first switch is closed and short-circuits the output terminals while the first switch is being affected by the magnetic field; and one of the contacts of the second switch is opened and disconnects one of the output terminals while the second switch is being affected by the magnetic field.
A handset microphone according to an aspect of the present invention is free of noise contamination during a switching operation and malfunction due to an external magnetic field.
A handset microphone according to an embodiment of the present invention will now be described with reference to the accompanying drawings.
The transmission switch 10 is a reed switch having a mechanism for moving position of a magnet in synchronization with the operation of an operational unit (not illustrated) of the handset microphone 100. During the quiescent state of the operational unit, the contact of the reed switch is magnetized by a magnetic field from the magnet. The contact of the transmission switch 10 is closed by the magnetic field. If no magnetic field is applied from the magnet, the contact of the transmission switch 10 is opened. That is, the transmission switch is a make-contact reed switch.
As illustrated in
If the operational unit of the handset microphone 100 is operated (for example, pressed), the magnet recedes from the contact. As a result, the contact is not affected by the magnetic field, then the contact is opened. In other words, if the operational unit is operated, speech signals are output from the output terminals of the microphone unit 30 depending on the state of the hook switch 20 described below.
More specifically, the output of the speech signals from the handset microphone 100 is switched by the transmission switch 10.
The hook switch 20 is a transfer contact reed switch and is switched from a normally closed contact to a normally open contact by the magnetic field.
The handset microphone 100 includes a housing (not illustrated) accommodating several components, such as the microphone unit 30, the transmission switch 10, and the hook switch 20 in the handset microphone 100. The housing has a hanging member for hanging the housing on a wall. The wall has a prefixed hook or holding member provided with a magnet. When the handset microphone 100 is not used, the hanging member is put on the hook (the holding member). The hook switch 20 is shifted to the normally open contact by the magnetic field from the magnet and maintains this state. In other words, the handset microphone 100 has output terminals opened or closed by the hook switch 20.
The hanging member of the housing of the handset microphone 100 is, for example, a hole provided in the housing. The hook (the holding member) is engageable with the hole in the housing to fix the handset microphone 100.
The handset microphone 100 can be switched with the hook switch 20 between the outputtable state and the output cutoff state.
A configuration of the transmission switch 10 will now be described in detail.
As illustrated in
In the transmission switch 10, the magnet is positioned so as to apply a magnetic field to the contact portion 13 when the operational unit is not operated, and so as to apply no magnetic field to the contact portion 13 when the operational unit is operated.
A configuration of the hook switch 20 will now be described.
The hook switch 20 includes a single reed and two reeds facing the single reed at a predetermined distance, all the reeds being enclosed in a glass tube 24. Two of the three reeds are ferromagnetic, one is a common (COM) reed 21, and the other is a normally open (NO) contact reed 23. The remaining one is a normally closed (NC) contact reed 22 having a nonmagnetic free end. The glass tube 24 is filled with inert gas 25 to prevent activation of the contact portion 26.
As illustrated in
The operation of the handset microphone 100 will now be explained.
The handset microphone 100 described in
The transmission switch 10 is then operated and changed to a speech transmission state in
The state illustrated in
The handset microphone 100 described above includes the hook switch 20 and the transmission switch 10, which are implemented by the reed switches. This configuration is free of noise contamination during a switching operation and malfunction due to an external magnetic field.
Number | Date | Country | Kind |
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2013-128963 | Jun 2013 | JP | national |