JP2501445B2 - Loud call circuit - Google Patents
Loud call circuitInfo
- Publication number
- JP2501445B2 JP2501445B2 JP7234587A JP7234587A JP2501445B2 JP 2501445 B2 JP2501445 B2 JP 2501445B2 JP 7234587 A JP7234587 A JP 7234587A JP 7234587 A JP7234587 A JP 7234587A JP 2501445 B2 JP2501445 B2 JP 2501445B2
- Authority
- JP
- Japan
- Prior art keywords
- voice
- microphone
- speaker
- circuit
- transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Description
【発明の詳細な説明】 [技術分野] 本発明は、いわゆるハンドフリー電話機などの拡声通
話回路において、マイクロホンなどの受話器からスピー
カなどの送話器へ音声が回り込むために生じるハウリン
グを、通話音声に影響を与えることなく防止することが
できる拡声通話回路に関するものである。Description: TECHNICAL FIELD The present invention, in a loudspeaker communication circuit such as a so-called hands-free telephone, describes howling, which occurs when a voice circulates from a receiver such as a microphone to a transmitter such as a speaker, as a communication voice. The present invention relates to a loudspeaker communication circuit that can be prevented without affecting.
[背景技術] 従来より提供されているこの種の拡声通話回路はハウ
リング防止のために送受話切換回路を備えた構成のもの
があり、第4図に示すように、送話信号線路Lt及び受話
信号線路Lrとの間に配設されて外部線路L上の信号を送
話信号及び受話信号とに分岐する防側音回路11と、送話
音声を受波するマイクロホンMと、送話信号線路Ltに設
けられてマイクロホンMの受波した音声を増幅するため
の増幅器OP11,OP12と、受話信号線路Lrに設けられ防側
音回路11を介して入力される受話信号を増幅して音声信
号を出力するための増幅器OP13,OP14と、増幅器OP14か
らの音声信号により受話音声を音声出力するスピーカSp
と、送話信号線路Lt及び受話信号線路Lrとの間に配設さ
れる送受話切換回路とで構成される。送受話切換回路
は、同図に示すように、送話信号線路Ltと受話信号線路
Lrとにそれぞれ挿入された一対の可変損失要素D1,D2を
備えており、送話信号線路Ltと受話信号線路Lrとの送話
及び受話信号を、それぞれ平滑回路Rc1,Rc2により平滑
した後、これらの信号レベルを比較器COで比較すると共
に、信号レベルの大小関係に対応したレベル検出信号を
出力する。ダイオードDd、抵抗R2、コンデンサC、抵抗
R1及びインバータIvでなる制御回路12は、このレベル検
出信号に応じて可変損失要素D1,D2の伝送損失を制御す
ることにより、信号レベルの小さいほうの送話信号線路
Ltもしくは受話信号線路Lrに挿入された可変損失要素
D1,D2の伝送損失を他方よりも大きくする構成となって
いる。即ち、相手が話し中で、受話信号のレベルが送話
信号の信号レベルより大きければ、比較器COのレベル検
出信号はLOWとなって点AはLOWであり、可変損失要素D1
はスイッチオフのままとなって、送話信号線路Ltに損失
が加えられて受話状態となる。逆に、送話時に、送話信
号の信号レベルが受話信号の信号レベルより大きけれ
ば、レベル検出信号はHIGHとなって接続点Aはコンデン
サC及び抵抗R1の時定数に従ってHIGHとなるため、イン
バータIvを介した可変損失要素D2がスイッチオフとなっ
て受話信号線路Lrに損失が加えられて送話状態となる。[Background Art] This type of public-speaking speech circuit conventionally provided has a configuration including a transmission / reception switching circuit for preventing howling. As shown in FIG. 4, a transmission signal line Lt and a reception signal line are provided. A protection side sound circuit 11 which is arranged between the signal line Lr and branches the signal on the external line L into a transmission signal and a reception signal, a microphone M for receiving the transmission voice, and a transmission signal line Amplifiers OP 11 and OP 12 provided in Lt for amplifying the voice received by the microphone M, and a voice that amplifies the received signal input through the protection side sound circuit 11 provided in the received signal line Lr Amplifiers OP 13 and OP 14 for outputting a signal, and a speaker Sp for outputting a received voice by a voice signal from the amplifier OP 14
And a transmission / reception switching circuit arranged between the transmission signal line Lt and the reception signal line Lr. As shown in the figure, the transmission / reception switching circuit consists of a transmission signal line Lt and a reception signal line.
It is provided with a pair of variable loss elements D 1 and D 2 respectively inserted in Lr, and the transmission and reception signals of the transmission signal line Lt and the reception signal line Lr are respectively smoothed by smoothing circuits Rc 1 and Rc 2. After smoothing, these signal levels are compared by the comparator CO and a level detection signal corresponding to the magnitude relation of the signal levels is output. Diode Dd, resistance R 2 , capacitor C, resistance
The control circuit 12 including the R 1 and the inverter Iv controls the transmission loss of the variable loss elements D 1 and D 2 in accordance with the level detection signal, so that the transmission signal line having the smaller signal level is transmitted.
Variable loss element inserted in Lt or receiving signal line Lr
The configuration is such that the transmission loss of D 1 and D 2 is larger than that of the other. That is, when the other party is talking and the level of the reception signal is higher than the signal level of the transmission signal, the level detection signal of the comparator CO becomes LOW, the point A is LOW, and the variable loss element D 1
Remains switched off, a loss is added to the transmission signal line Lt, and the reception state is established. On the other hand, when the signal level of the transmission signal is higher than the signal level of the reception signal during transmission, the level detection signal becomes HIGH and the connection point A becomes HIGH according to the time constant of the capacitor C and the resistor R 1 , The variable loss element D 2 via the inverter Iv is switched off, and loss is added to the reception signal line Lr to enter the transmission state.
このようにして、受話器であるマイクロホンMと送話
器であるスピーカSpとを含む伝送ループ、即ち、防側音
回路11、増幅器OP13、増幅器OP14、スピーカSp、マイク
ロホンM、増幅器OP11、増幅器OP12を介して再び防側音
回路11に至る閉ループ内の増幅率を1以下にするように
し、スピーカSpからマイクロホンMへの音声の回り込み
によるハウリングの発生を防止しているのである。しか
しこのような方式では、両可変損失要素D1,D2の動作切
換動作による受話状態と送話状態との切換が、音声の語
頭や語尾でうまく行なわれず、受話音声の語尾が途切れ
たり、送話音声の語頭が切れたりして、ハウリング防止
のために、送受話音声に悪影響を与えるという欠点があ
る。In this way, a transmission loop including the microphone M, which is the receiver, and the speaker Sp, which is the transmitter, that is, the protection sound circuit 11, the amplifier OP 13 , the amplifier OP 14 , the speaker Sp, the microphone M, and the amplifier OP 11 , The amplification factor in the closed loop that reaches the anti-sidephone circuit 11 again via the amplifier OP 12 is set to 1 or less to prevent howling from occurring due to the wraparound of the sound from the speaker Sp to the microphone M. However, in such a system, switching between the receiving state and the transmitting state by the operation switching operation of both variable loss elements D 1 and D 2 is not performed well at the beginning or ending of the voice, and the ending of the receiving voice is interrupted, There is a drawback that the head of the transmitted voice is cut off and the transmitted and received voice is adversely affected to prevent howling.
[発明の目的] 本発明は上述の問題点に鑑みて為されたものであり、
送受話切換回路を必要とせず、容易に誤頭及び語尾切断
のないハウリング防止ができる拡声通話回路を提供する
ことを目的とする。[Object of the Invention] The present invention has been made in view of the above problems,
It is an object of the present invention to provide a loudspeaker communication circuit which does not require a transmission / reception switching circuit and can easily prevent howling without misleading or ending of the ending.
[発明の開示] 本発明の拡声通話回路のハウリング防止方式は、送話
信号線路及び受話信号線路と外部線路との間に配設され
て送話信号と受話信号とを分離するための防側音回路
と、送話音声を受波するための受波手段と、受波手段に
より受波した音声を増幅すると共に送話信号線路を介し
て防側音回路へ送話信号を出力する第1の増幅器と、防
側音回路を介して入力される受話信号を増幅してスピー
カにより音声出力するための第2の増幅器とからなる拡
声通話回路に於いて、上記受波手段が、スピーカの中心
軸に対して互いに対称に配置される指向性のマイクロホ
ン及び無指向性のマイクロホンと、無指向性のマイクロ
ホン及び指向性のマイクロホンからの両出力の差を出力
する差動増幅器とからなる構成となっているので、スピ
ーカ出力音声は、指向性及び無指向性のマイクロホンに
より同等に受波されて差動増幅器により消去され、無指
向性のマイクロホンに入力される送話側の音声のみが送
話音声となり、送話や受話の信号回路に可変損失要素を
配設した送受話切換回路を使用することなく、可変損失
要素の切換動作による語頭及び語尾切断のないハウリン
グ防止ができるものである。DISCLOSURE OF THE INVENTION A method for preventing howling in a loudspeaker communication circuit according to the present invention is provided between a transmitting signal line and a receiving signal line and an external line to separate a transmitting signal and a receiving signal from each other. A sound circuit, a wave receiving means for receiving the transmitted voice, and a voice for amplifying the voice received by the wave receiving means and for outputting a voice transmitting signal to a protection side sound circuit via a voice transmitting signal line. And a second amplifier for amplifying a reception signal input through the protection side sound circuit and outputting a voice by a speaker, in the loudspeaker communication circuit, the receiving means is the center of the speaker. It is composed of a directional microphone and an omnidirectional microphone that are arranged symmetrically with respect to the axis, and a differential amplifier that outputs the difference between the outputs from the omnidirectional microphone and the directional microphone. The speaker The force voice is equally received by the directional and omnidirectional microphones and canceled by the differential amplifier, and only the voice on the transmitting side input to the omnidirectional microphone becomes the transmitting voice. It is possible to prevent howling without leading and ending of a word due to a switching operation of a variable loss element without using a transmission / reception switching circuit in which a variable loss element is arranged in a signal circuit for receiving a voice.
実施例 本発明の拡声通話回路は、第1図に示すように、送話
信号線路Lt及び受話信号線路Lrと外部線路Lとの間に配
設されて送話信号と受話信号とを分離するための防側音
回路1と、送話音声を受波して受波音声に応じた信号を
出力する受波手段2と、送話信号線路Ltに設けられて受
波手段2により受波した音声を増幅して送話信号を出力
する第1の増幅器OP1と、受話信号線路Lrに設けられて
防側音回路1から入力される受話信号を増幅してスピー
カSpにより音声出力するための音声信号を出力する第2
の増幅器OP2とからなる。EXAMPLE As shown in FIG. 1, the loudspeaker circuit of the present invention is arranged between the transmission signal line Lt and the reception signal line Lr and the external line L to separate the transmission signal and the reception signal. For preventing noise, a wave receiving means 2 for receiving the transmitted voice and outputting a signal corresponding to the received voice, and a wave receiving means 2 provided on the transmitted signal line Lt for receiving the wave. A first amplifier OP 1 that amplifies a voice and outputs a transmission signal, and a first amplifier OP 1 that is provided in the reception signal line Lr and amplifies the reception signal input from the protection side sound circuit 1 to output the sound by the speaker Sp. Second output audio signal
Amplifier OP 2 of.
受波手段2は、マイクボックスBに埋設された指向性
及び無指向性のマイクロホンM1,M2と、第1の増幅器OP1
の前段に設けられて両マイクロホンM1,M2の一対の音声
信号の出力により両音声信号の差のみ出力する差動増幅
器Dopとで構成される。受波手段2の一対のマイクロホ
ンM1,M2は、同様の無指向性マイクロホンでよく、所定
の形状に形成されたマイクボックスBに埋設されること
により、一方は指向性のマイクロホンM1、他方は無指向
性のマイクロホンM2となる。マイクボックスBは、第2
図に示すように、一方のマイクロホンM1を埋設するため
の凹部6が形成してあり、埋設されたマイクロホンM
1は、一面のみが受波面としてマイクボックスB前面に
露呈するため、単一指向性を持つことになる。また、マ
イクボックスBには、他方のマイクロホンM2を埋設する
ために、前面から後面に至る空洞部5を形成して前面及
び後面に開口7,8が形成され、マイクロホンM2が空洞部
5内に埋設されて前面が受波面としてマイクボックスB
の前面に露呈する。マイクロホンM2の背方面は空洞部5
の開口7を通してマイクボックスB後面側に他の受波面
として露出するためマイクロホンM2はマイクボックスB
前方及び後方に指向性を持つことになる。このように一
対のマイクロホンM1,M2を埋設したマイクボックスB
は、スピーカSp振動面の前方に設置され、マイクボック
スBの前面がスピーカSp振動面に対面して両マイクロホ
ンM1,M2の受波面がスピーカSp前面に対面すると共に、
両マイクロホンM1,M2の受波面がスピーカSp振動面に向
け且つスピーカSpの中心軸に対して対称に配置されるこ
とにより、両マイクロホンM1,M2がスピーカSpの出力音
声を同様の音声レベルで受波できるようにしてある。The wave receiving means 2 includes directional and omnidirectional microphones M 1 and M 2 embedded in a microphone box B and a first amplifier OP 1.
And a differential amplifier Dop that is provided in the preceding stage and outputs only the difference between the two audio signals by the output of a pair of audio signals from both microphones M 1 and M 2 . The pair of microphones M 1 and M 2 of the wave receiving means 2 may be similar omnidirectional microphones, and by being embedded in a microphone box B formed in a predetermined shape, one of them is a directional microphone M 1 , The other is an omnidirectional microphone M 2 . The microphone box B is the second
As shown in the figure, a recess 6 for embedding one microphone M 1 is formed, and the embedded microphone M
In the case of 1 , only one surface is exposed on the front surface of the microphone box B as a wave receiving surface, and therefore, it has unidirectionality. Further, the microphone box B, and for embedding the other microphones M 2, to form a cavity 5 extending from the front surface to the rear surface is opened 7,8 formed on the front and rear surfaces, the microphone M 2 is the cavity 5 Microphone box B is buried inside and the front surface is the receiving surface.
Exposed in front of. The back side of the microphone M 2 is a cavity 5
The microphone M 2 is exposed on the rear surface side of the microphone box B through the opening 7 as another receiving surface.
It will have directivity in the front and rear. In this way, the microphone box B in which the pair of microphones M 1 and M 2 are embedded
Is installed in front of the speaker Sp vibrating surface, the front surface of the microphone box B faces the speaker Sp vibrating surface, and the receiving surfaces of both microphones M 1 and M 2 face the speaker Sp front surface.
By arranging the receiving surfaces of the microphones M 1 and M 2 toward the vibration surface of the speaker Sp and symmetrically with respect to the center axis of the speaker Sp, both microphones M 1 and M 2 output the sound output from the speaker Sp similarly. It is possible to receive at the voice level.
このような構成により、通話者の音声は無指向性マイ
クロホンM2のみに入力され、スピーカSpからの出力音声
は、指向性及び無指向性の両マイクロホンM1,M2に入力
されるので、差動増幅器Dopの出力からスピーカSp音声
のみが消去されて送話音声のみとなる。以下に動作を説
明する。With such a configuration, the voice of the caller is input only to the omnidirectional microphone M 2 , and the output voice from the speaker Sp is input to both the directional and omnidirectional microphones M 1 and M 2 . Only the speaker Sp voice is erased from the output of the differential amplifier Dop and only the transmitted voice becomes. The operation will be described below.
通話者がマイクボックスB側に向かって音声を発する
と、通話者の音声は、マイクボックスBの後方側の開口
7を通して露出する無指向性のマイクロホンM2のみに受
波され、他方の指向性のマイクロホンM1には入力されな
い。従って、差動増幅器Dopには、通話者の音声の音声
信号のみが入力され、指向性のマイクロホンM1からは音
声入力がないので、通話者の音声のみが第1の増幅器OP
1により増幅されて送話信号として防側音回路1、外部
線路Lを介して相手側へ送信される。When the caller makes a voice toward the microphone box B side, the voice of the caller is received only by the omnidirectional microphone M 2 exposed through the opening 7 on the rear side of the microphone box B, and the other directivity is received. No input to the microphone M 1 . Therefore, only the voice signal of the caller's voice is input to the differential amplifier Dop, and no voice is input from the directional microphone M 1. Therefore, only the caller's voice is input to the first amplifier OP.
Amplified by 1 and transmitted as a transmission signal to the other party through the protection side sound circuit 1 and the external line L.
また、相手側から外部線路L、防側音回路1を介して
第2の増幅器OP2へ入力された受話信号は、増幅されて
スピーカSpにより出力される。スピーカSpにより出力さ
れた音声は、マイクボックスBに埋設された一対のマイ
クロホンM1,M2によって共に、同時に同様の音声レベル
で受波され、同時間、同形状の音声信号が差動増幅器Do
pに入力される。従って、第1の増幅器OP1への差動増幅
器Dopからの送話信号にはスピーカSpの音声が含まれ
ず、従来の回路で存在した防側音回路1、第2の増幅器
OP2、スピーカSp、受波手段2、差動増幅器Dop、第1の
増幅器OP1を介して再び防側音回路1に至るハウリング
発生の閉ループが、差動増幅器Dopにおいて中断される
ことになり、通話装置内で形成されるハウリング発生が
防止される。Further, the reception signal input from the other side to the second amplifier OP 2 via the external line L and the soundproofing sound circuit 1 is amplified and output by the speaker Sp. The voice output from the speaker Sp is simultaneously received by the pair of microphones M 1 and M 2 embedded in the microphone box B at the same voice level, and a voice signal of the same shape and at the same time is output by the differential amplifier Do.
entered in p. Therefore, the voice signal of the speaker Sp is not included in the transmission signal from the differential amplifier Dop to the first amplifier OP 1 , and the protection side sound circuit 1 and the second amplifier existing in the conventional circuit are present.
The closed loop of howling generation, which reaches OPD 1 again via OP 2 , speaker Sp, wave receiving means 2, differential amplifier Dop, and first amplifier OP 1 , is interrupted in differential amplifier Dop. The occurrence of howling formed in the communication device is prevented.
上記実施例で述べたように、本発明のハウリング防止
方式は、スピーカ出力音声が指向性及び無指向性のマイ
クロホンM1,M2により同等に受波されて差動増幅器Dopに
より消去され、無指向性のマイクロホンM2に入力される
送話側の音声のみが送話音声となるので、従来のよう
に、可変損失要素を配置する送受話切換回路を使用せ
ず、語頭及び語尾切断のないハウリング防止を行なうこ
とができるのである。As described in the above embodiment, in the howling prevention method of the present invention, the speaker output sound is equally received by the directional and omnidirectional microphones M 1 and M 2 , and is erased by the differential amplifier Dop. Since only the voice on the transmitting side that is input to the directional microphone M 2 becomes the transmitting voice, there is no use of a transmission / reception switching circuit that arranges a variable loss element as in the conventional case, and there is no beginning or ending disconnection. Howling can be prevented.
ここで、上記実施例では、第2図に示すような形状の
マイクボックスBの形状を使用したが、マイクボックス
B1の空洞部5の後面側の形状を、第3図に示すような断
面形状のホーン型形状にし、このホーンHにより無指向
性のマイクロホンM2の受話側受波面の指向性を強化した
マイクボックスB1を使用し、スピーカSpの出力音声がマ
イクロボックスB1側方から後面にかけて回り込み、受話
側の受波面にスピーカSp出力が受波されることを防止す
る構成としてもよい。または、マイクロホンM1,M2の特
性自体が指向性及び無指向性であって、特別なマイクボ
ックスなどを使用しない構成としてもよい。Here, in the above embodiment, the shape of the microphone box B having the shape shown in FIG. 2 was used.
The shape of the rear surface side of the cavity portion 5 of B 1 is a horn shape having a cross-sectional shape as shown in FIG. 3, and this horn H enhances the directivity of the receiving side receiving surface of the omnidirectional microphone M 2 . The microphone box B 1 may be used to prevent the output sound of the speaker Sp from wrapping around from the side of the micro box B 1 to the rear surface and preventing the speaker Sp output from being received by the receiving surface of the receiving side. Alternatively, the characteristics of the microphones M 1 and M 2 themselves may be directional and omnidirectional, and a special microphone box or the like may not be used.
[発明の効果] 本発明の拡声通話回路のハウリング防止方式は、送話
信号線路及び受話信号線路と外部線路との間に配設され
て送話信号と受話信号とを分離するための防側音回路
と、送話音声を受波するための受波手段と、受波手段に
より受波した音声を増幅すると共に送話信号線路を介し
て防側音回路へ送話信号を出力する第1の増幅器と、防
側音回路を介して入力される受話信号を増幅してスピー
カにより音声出力するための第2の増幅器とからなる拡
声通話回路に於いて、上記受波手段が、スピーカの中心
軸に対して互いに対称に配置される指向性のマイクロホ
ン及び無指向性のマイクロホンと、無指向性のマイクロ
ホン及び指向性のマイクロホンからの両出力の差を出力
する差動増幅器とからなる構成となっているので、スピ
ーカ出力音声は、指向性及び無指向性のマイクロホンに
より同等に受波されて受波手段の差動増幅器により消去
され、無指向性のマイクロホンに入力される送話側の音
声のみが送話音声となり、送話や受話の信号回路に可変
損失要素を配設する送受話切換回路を使用することな
く、可変損失要素の切換動作による語頭及び語尾切断の
ないハウリング防止ができるという効果を奏する。[Advantage of the Invention] A method for preventing howling of a loudspeaker communication circuit according to the present invention is provided between a transmission signal line and a reception signal line and an external line to prevent the transmission signal and the reception signal from being separated. A sound circuit, a wave receiving means for receiving the transmitted voice, and a voice for amplifying the voice received by the wave receiving means and for outputting a voice transmitting signal to a protection side sound circuit via a voice transmitting signal line. And a second amplifier for amplifying a received signal input through the protection side sound circuit and outputting the sound by a speaker, in the loudspeaker communication circuit, the receiving means is the center of the speaker. It is composed of a directional microphone and an omnidirectional microphone that are arranged symmetrically with respect to the axis, and a differential amplifier that outputs the difference between the outputs from the omnidirectional microphone and the directional microphone. The speaker The force voice is equally received by the directional and omnidirectional microphones and is erased by the differential amplifier of the wave receiving means, and only the voice on the transmitting side input to the omnidirectional microphone becomes the transmitting voice. It is possible to prevent howling without disconnection of the beginning and the ending of a word due to the switching operation of the variable loss element without using a transmission / reception switching circuit in which a variable loss element is arranged in a signal circuit for transmission and reception.
第1図は本発明の実施例のハウリング防止方式の構成を
示すブロック回路図、第2図は同様の一対のマイクロホ
ンM1,M2のマイクボックスBへの埋設状態を示す部分横
断面図、第3図は同様のマイクボックスBの他の例を示
す部分横断面図、第4図は拡声通話回路に配設された従
来の送受話切換回路を示すブロック回路図であり、1は
防側音回路、2は受波手段、Dopは差動増幅器、Lは外
部線路、Lrは受話信号線路、Ltは送話信号線路、M1は指
向性のマイクロホン、M2は無指向性のマイクロホン、OP
1は第1の増幅器、OP2は第2の増幅器、Spはスピーカで
ある。FIG. 1 is a block circuit diagram showing a structure of a howling prevention system according to an embodiment of the present invention, and FIG. 2 is a partial cross-sectional view showing a state in which a pair of similar microphones M 1 and M 2 are embedded in a microphone box B, FIG. 3 is a partial cross-sectional view showing another example of the same microphone box B, and FIG. 4 is a block circuit diagram showing a conventional transmission / reception switching circuit arranged in a loudspeaker communication circuit, and 1 is a protection side. Sound circuit, 2 is a receiving means, Dop is a differential amplifier, L is an external line, Lr is a receiving signal line, Lt is a transmitting signal line, M 1 is a directional microphone, M 2 is an omnidirectional microphone, OP
1 is a first amplifier, OP 2 is a second amplifier, and Sp is a speaker.
Claims (1)
との間に配設されて送話信号と受話信号とを分離するた
めの防側音回路と、送話音声を受波するための受波手段
と、受波手段により受波した音声を増幅すると共に送話
信号線路を介して防側音回路へ送話信号を出力する第1
の増幅器と、防側音回路を介して入力される受話信号を
増幅してスピーカにより音声出力するための第2の増幅
器とからなる拡声通話回路に於いて、上記受波手段が、
スピーカの中心軸に対して互いに対称に配置される指向
性のマイクロホン及び無指向性のマイクロホンと、無指
向性のマイクロホン及び指向性のマイクロホンからの両
出力の差を出力する差動増幅器とからなる拡声通話回
路。1. An anti-sidetone circuit arranged between a transmission signal line and a reception signal line and an external line for separating a transmission signal and a reception signal, and for receiving a transmission voice. And a sound receiving means for amplifying the sound received by the wave receiving means and outputting a transmission signal to the protection side sound circuit via the transmission signal line.
And a second amplifier for amplifying a received signal input through the protection side sound circuit and outputting a voice by a speaker, the wave receiving means comprises:
It consists of a directional microphone and an omnidirectional microphone that are arranged symmetrically with respect to the center axis of the speaker, and a differential amplifier that outputs the difference between the outputs of the omnidirectional microphone and the directional microphone. Loudspeaker call circuit.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7234587A JP2501445B2 (en) | 1987-03-26 | 1987-03-26 | Loud call circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP7234587A JP2501445B2 (en) | 1987-03-26 | 1987-03-26 | Loud call circuit |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS63238753A JPS63238753A (en) | 1988-10-04 |
JP2501445B2 true JP2501445B2 (en) | 1996-05-29 |
Family
ID=13486623
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP7234587A Expired - Lifetime JP2501445B2 (en) | 1987-03-26 | 1987-03-26 | Loud call circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2501445B2 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4640210B2 (en) * | 2006-02-23 | 2011-03-02 | パナソニック電工株式会社 | Telephone device |
JP4853382B2 (en) * | 2007-05-28 | 2012-01-11 | パナソニック電工株式会社 | Telephone device |
-
1987
- 1987-03-26 JP JP7234587A patent/JP2501445B2/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
JPS63238753A (en) | 1988-10-04 |
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