JPH028447Y2

JPH028447Y2 -

Info

Publication number: JPH028447Y2
Application number: JP7879482U
Authority: JP
Priority date: 1982-05-27
Filing date: 1982-05-27
Publication date: 1990-02-28
Also published as: JPS58182542U

Description

【考案の詳細な説明】本考案は音声がスピーカから拡声される拡声電
話機に関する。特に、既設の押ボタンダイヤル電
話機に付加し得る付加形拡声電話機に関するもの
である。[Detailed Description of the Invention] The present invention relates to a public address telephone that amplifies voices through speakers. In particular, the present invention relates to an add-on loudspeaker telephone that can be added to an existing pushbutton dial telephone.

従来この種の電話機として、押ボタンダイヤル
を含む電話機と拡声回路とを一体にしたもの、あ
るいは付加形のものとしては単に加入者線路を切
替えて接続するものが知られている。前者は通常
の送受器と拡声回路とが一体となつているため、
電話機が既に設置されている場所に拡声電話機を
設置する場合には、既設の電話機を取りはずし新
らたに一体形の拡声電話機を取付けなければなら
ず不経済であつた。また後者の場合は、既設の電
話機ははそのまま使用できるが単に加入者線路を
スイツチで切替えて使用するため、拡声によるダ
イヤル発信が不可能であり、送受器を取り上げて
ダイヤルした後に拡声回路に切替えなければなら
ず、操作上の不都合があつた。 Conventionally, as this type of telephone, there are known telephones in which a telephone including a pushbutton dial and a loudspeaker circuit are integrated, or, as an additional type, a telephone in which subscriber lines are simply switched and connected. The former is a combination of a normal handset and amplification circuit, so
When installing a loudspeaker telephone in a place where a telephone is already installed, the existing telephone must be removed and a new integrated loudspeaker telephone installed, which is uneconomical. In the latter case, the existing telephone can be used as is, but because the subscriber line is simply switched and used, it is impossible to make a dialing call using amplification, and after picking up the handset and dialing, the telephone is switched to the amplification circuit. This caused operational inconvenience.

この他に、電話機の防側音回路を兼用する方
法、すなわち電話機の送話器と受話器の接続端子
で拡声回路の送話回路および受話回路を切替え、
拡声電話による押ボタンダイヤル発信を可能にす
る方法も考えられた。しかし、送受器の防側音回
路では側音減衰量が十分大きくとれないため、拡
声回路の鳴音ループ利得が大きくなり、拡声回路
の送話および受話回路の利得を十分大きくとれな
い欠点がある。これを回避するため、音声スイツ
チ回路を用いると、拡声回路ではその音声スイツ
チの減衰量を大きくしなければならず、拡声によ
る通話の品質が劣化することになるため実用化さ
れなかつた。 In addition to this, there is a method in which the telephone's side sound protection circuit is also used, that is, the transmitting circuit and the receiving circuit of the loudspeaker circuit are switched using the connecting terminal of the telephone's transmitter and handset.
A method to enable push-button dialing using a public address telephone was also considered. However, because the side-tone attenuation in the side-tone protection circuit of the handset cannot be sufficiently large, the sound loop gain of the loudspeaker circuit becomes large, and the gain of the loudspeaker circuit's transmitting and receiving circuits cannot be made sufficiently large. . In order to avoid this, if an audio switch circuit is used, the loudspeaker circuit must increase the amount of attenuation of the audio switch, which deteriorates the quality of the voice call due to the loudspeaker, so it has not been put to practical use.

本考案はこのような欠点を除去し、既設の押ボ
タンダイヤル電話機との簡単な配線接続によつて
付加することができ、拡声によるダイヤル発信を
可能にした付加形拡声電話機を提供することを目
的とする。 The purpose of the present invention is to eliminate such drawbacks and provide an additional loudspeaker telephone that can be attached to an existing push-button dial telephone by simple wiring connection, and that enables dialing by loudspeaker. shall be.

すなわち、本考案の装置は、加入者電話機とし
て広く知られている押ボタン電話機に付加して使
用する装置であつて、その付加配線を既設の押ボ
タンダイヤル電話機の改造を必要とせずに実行す
ることができるとともに、拡声電話機の機械スイ
ツチを操作すれば、押ボタン電話機の送受器ハン
ドセツトを持上げなくともダイヤル操作ができる
ところに特徴がある。 That is, the device of the present invention is a device that is used in addition to a pushbutton telephone widely known as a subscriber telephone, and the additional wiring can be carried out without the need to modify the existing pushbutton dial telephone. In addition, by operating the mechanical switch on the loudspeaker telephone, dialing can be performed without having to lift the handset of the push-button telephone.

本考案の装置には、マイクロホンと、送話増幅
器と、防側音回路と、受話増幅器と、スピーカと
を含む拡声回路を備え、この入出力音声信号は結
合トランスと、CR直列回路と、ダイオードブリ
ツジとをそれぞれ介して、外線に結合される。ま
たこの拡声回路の送話増幅器および受話増幅器は
その利得を低減することができるように構成さ
れ、押ボタン電話機のダイヤルが操作されたとき
に生じる電圧をホトカプラを介して検出して、こ
れにより上記利得を低減するように構成される。
また使用者が操作する機械スイツチを設け、この
機械スイツチには連動する２個のメーク接点組と
２個の切替接点組を備え、この各接点組により、
拡声電話装置との切替えおよび通話電流ループの
開閉を行うように構成される。 The device of the present invention is equipped with a loudspeaker circuit including a microphone, a transmitting amplifier, a side sound protection circuit, a receiving amplifier, and a speaker, and this input/output audio signal is transmitted through a coupling transformer, a CR series circuit, and a diode. and a bridge, respectively, to the outside line. In addition, the transmitting amplifier and the receiving amplifier of this public address circuit are configured to be able to reduce their gains, and detect the voltage generated when the dial of the pushbutton telephone is operated via a photocoupler, thereby detecting the above-mentioned voltage. configured to reduce gain.
In addition, a mechanical switch operated by the user is provided, and this mechanical switch is equipped with two interlocking make contact sets and two switching contact sets, and each contact set allows
It is configured to switch with the loudspeaker telephone device and open and close the speech current loop.

次に本考案の実施例について図面を参照して説
明する。 Next, embodiments of the present invention will be described with reference to the drawings.

図は本考案の実施例回路図である。押ボタンダ
イヤル電話機１は外線端子２および３、ベル４、
フツクスイツチ５、ダイオードブリツジ６を備え
る。符号７で示す破線で囲む部分は押ボタンダイ
ヤルの回路であつて、発振回路OSC、タンク回
路TC、ダイオードD₁およびD₂、ダイヤルの押ボ
タンを押すことにより動作する機械スイツチ
SW、前記発振回路OSCに電流を供給する第一の
接続端子７−１、ダイヤル時に通話ループ電流を
断つ第二の接続端子７−２、通話ループ電流およ
び前記発振回路OSCに前記機械スイツチSWを介
し電流を供給する第三の接続端子７−３、ダイヤ
ル時に前記ダイオードD₂を介し直流電流を出力
して受話器のモニタ音を減衰制御する第四の接続
端子７−４とを含む。さらに前記押ボタンダイヤ
ル７の接続端子７−１〜７−４に対応して設けら
れた端子９〜１２を含む送受器回路８を備える。
さらに端子１３−１〜１３−３を含む中継端子板
１３を備える。 The figure is a circuit diagram of an embodiment of the present invention. The pushbutton dial telephone 1 has outside line terminals 2 and 3, a bell 4,
It is equipped with a switch 5 and a diode bridge 6. The part surrounded by a broken line indicated by numeral 7 is the pushbutton dial circuit, which includes an oscillation circuit OSC, a tank circuit TC, diodes D ₁ and D ₂ , and a mechanical switch that is activated by pressing the pushbutton on the dial.
SW, a first connection terminal 7-1 that supplies current to the oscillation circuit OSC, a second connection terminal 7-2 that cuts off the call loop current when dialing, a mechanical switch SW that connects the call loop current and the oscillation circuit OSC. and a fourth connection terminal 7-4 that outputs a direct current through the diode _D2 during dialing to control the attenuation of the monitor sound of the telephone receiver. Furthermore, a handset/receiver circuit 8 including terminals 9 to 12 provided corresponding to the connection terminals 7-1 to 7-4 of the pushbutton dial 7 is provided.
Furthermore, a relay terminal board 13 including terminals 13-1 to 13-3 is provided.

この押ボタンダイヤル電話機１に付加形拡声電
話機２１が付加接続される。この付加形拡声電話
機２１は、外線端子２′，L₁および３′，L₂、ダ
イオードブリツジ２２を備える。また拡声による
通話のとき使用者が操作し作動する機械スイツチ
２３を備える。この機械スイツチ２３は連動する
第一のメーク接点組２３−１、第二の切替接点組
２３−２、第三の切替接点組２３−３、および第
四のメーク接点組２３−４を含む。さらに、チヨ
ークコイル２４、CR直列回路２５、一次巻線端
子２６−１および２６−２を含む結合トランス２
６、マイクロホン２８、増幅利得を減衰できるよ
う構成された送話増幅器２９、防側音回路３０、
利得を低減できるよう構成された受話増幅器３
１、およびスピーカ３２を含む拡声回路２７、お
よび発光ダイオードとホトトランジスタを内蔵し
たホトカプラ３３とを備える。これらは図示のよ
うに結線される。 An additional loudspeaker telephone 21 is additionally connected to this pushbutton dial telephone 1. This additional type loudspeaker telephone 21 includes outside line terminals 2', L ₁ and 3', L ₂ and a diode bridge 22. It also includes a mechanical switch 23 that is operated by the user when making a call using amplified sound. This mechanical switch 23 includes a first make contact set 23-1, a second switching contact set 23-2, a third switching contact set 23-3, and a fourth make contact set 23-4, which are interlocked. Further, a coupling transformer 2 including a chiyoke coil 24, a CR series circuit 25, and primary winding terminals 26-1 and 26-2.
6, a microphone 28, a transmitting amplifier 29 configured to attenuate the amplification gain, a side sound protection circuit 30,
Receiving amplifier 3 configured to reduce gain
1, a loudspeaker circuit 27 including a speaker 32, and a photocoupler 33 containing a light emitting diode and a phototransistor. These are wired as shown.

次に通話時とダイヤル発信時の動作について、
拡声の状態と送受器を使用する状態に分けて説明
する。なお、加入者線路より供給され外線ピン端
子L₁およびL₂に加わる直流電圧の極性について
は第一のダイオードブリツジ６および第二のダイ
オードブリツジ２２にて極性が装置内部で単一に
なるよう構成されているが、ここでは説明の都合
上外線端子２′に正、外線端子３′に負の電位が加
わつている場合について以下説明する。 Next, regarding the operation when making a call and dialing,
The explanation will be divided into the state of amplification and the state of using a handset. Note that the polarity of the DC voltage supplied from the subscriber line and applied to the outside line pin terminals L ₁ and L ₂ is unified inside the device at the first diode bridge 6 and the second diode bridge 22. However, for convenience of explanation, a case will be described below in which a positive potential is applied to the external line terminal 2' and a negative potential is applied to the external line terminal 3'.

まず拡声を使用する場合について説明すると、
拡声電話を行う場合には機械スイツチ２３を操作
して作動させると、第一および第四のメーク接点
組２３−１，２３−４および第二、第三の切替接
点組２３−２，２３−３はメーク接点側に閉じ
る。従つて通話電流は、外線ピン端子２′−ダイ
オードブリツジ２２の正出力端−第三の切替接点
組２３−３−中継端子板１３のピン端子１３−２
−押ボタンダイヤル７の第三の接続端子７−３を
経由して機械スイツチSWのブレーク接点−第二
の接続端子７−２−中継端子板１３の端子１３−
１−第二の切替接点組２３−２−結合トランス２
６−ダイオードブリツジ２２の負出力端−外線端
子３′と流れて電流ループが形成される。 First, let me explain when using amplification.
When making a loudspeaker call, when the mechanical switch 23 is operated, the first and fourth make contact sets 23-1, 23-4 and the second and third switching contact sets 23-2, 23- are activated. 3 closes on the make contact side. Therefore, the communication current flows through the external line pin terminal 2', the positive output terminal of the diode bridge 22, the third switching contact set 23-3, and the pin terminal 13-2 of the relay terminal board 13.
- Break contact of mechanical switch SW via third connection terminal 7-3 of pushbutton dial 7 - Second connection terminal 7-2 - Terminal 13 of relay terminal board 13 -
1-Second switching contact set 23-2-Coupling transformer 2
A current loop is formed by flowing from the negative output terminal of the 6-diode bridge 22 to the external line terminal 3'.

拡声回路２７は結合トランス２６を介して加入
者線路L₁，L₂に接続され、拡声通話が可能な状
態となる。また結合トランス２６の端子２６−１
は第一のメーク接点組２３−１を経由してチヨー
クコイル２４を介し端子９に接続されているが、
第二の切替接点組２３−２が開いているため電話
機側の送話器Ｔには電流が流れず送話器Ｔは動作
しない。またこのとき送受器を取り上げフツクス
イツチ５が閉じても、ダイオードブリツジ６を介
する直流電流ループは、第三の切替接点側２３−
３が開き、かつ送受器回路８内の２個のコンデン
サにより阻止されて直流ループは形成されない。
またダイオードブリツジ６のダイオードにより交
流的に加入者線路２，３と遮断されるため、拡声
による通話性能には何ら影響を与えない。 The loudspeaker circuit 27 is connected to the subscriber lines L ₁ and L ₂ via the coupling transformer 26, so that loudspeaker communication is possible. Also, the terminal 26-1 of the coupling transformer 26
is connected to the terminal 9 via the first make contact set 23-1 and the check coil 24,
Since the second switching contact set 23-2 is open, current does not flow through the transmitter T on the telephone side and the transmitter T does not operate. At this time, even if the handset is picked up and the switch 5 is closed, the DC current loop passing through the diode bridge 6 continues through the third switching contact side 23-
3 is open and blocked by two capacitors in the handset circuit 8 so that no DC loop is formed.
Furthermore, since the diode of the diode bridge 6 disconnects the subscriber lines 2 and 3 in an alternating current manner, it does not affect the communication performance by amplification at all.

次にこの拡声通話状態におけるダイヤル発信に
ついて説明すると、機械スイツチ２３を作動させ
た状態で、押ボタンダイヤル電話機１の押ボタン
ダイヤル７のボタンを操作すると、この押ボタン
ダイヤル７の機械スイツチSWが動作し、第一の
電流ループが外線端子２′−ダイオードブリツジ
２２の正出力端−第三の切替接点組２３−３−端
子１３−３−第三の接続端子７−３−スイツチ
SWのメーク接点−発振回路OSC−第一の接続端
子７−１−端子９−端子１３−１−第一のメーク
接点組２３−１−ダイオードブリツジ２２の負出
力端−外線端子３′のように形成される。また途
中スイツチSWのメーク接点より分岐し、第二の
電流ループがダイオードD₂−第四の接続端子７
−４−中継端子板１３の端子１３−３−ホトカプ
ラ３３の発光ダイオード部分を経由し、端子１２
から送受器回路を経由して端子９−チヨークコイ
ル２４−第一のメーク接点組２３−１−ダイオー
ドブリツジ２２の負出力端−外線端子L₂のよう
に形成される。また、結合トランス２６を経由す
る電流ループは押ボタンダイヤル７のスイツチ
SWのブレーク接点により断となる。 Next, to explain dialing in this loudspeaker call state, when the button on the pushbutton dial 7 of the pushbutton dial telephone 1 is operated while the mechanical switch 23 is activated, the mechanical switch SW of the pushbutton dial 7 is activated. The first current loop connects the external line terminal 2' - the positive output terminal of the diode bridge 22 - the third switching contact set 23 - 3 - the terminal 13 - 3 - the third connection terminal 7 - 3 - the switch.
Make contact of SW - Oscillation circuit OSC - First connection terminal 7-1 - Terminal 9 - Terminal 13-1 - First make contact set 23-1 - Negative output end of diode bridge 22 - External line terminal 3' It is formed like this. In addition, the second current loop branches from the make contact of the switch SW on the way and connects to the diode D ₂ - fourth connection terminal 7.
-4-Terminal 12 of relay terminal board 13 via terminal 13-3-light emitting diode part of photocoupler 33
Terminal 9 - York coil 24 - First make contact set 23 - 1 - Negative output terminal of diode bridge 22 - External line terminal L ₂ are formed from the terminal 9 through the handset circuit. In addition, the current loop passing through the coupling transformer 26 is connected to the switch of the push button dial 7.
It is disconnected by the SW break contact.

この状態で第一の電流ループは押ボタンダイヤ
ル７の発振回路OSCを駆動し、加入者線路へ押
ボタンダイヤル信号を送出するが、このとき、
CR直列回路２５と結合トランス２６の直列回路
が、交流的に加入者線路に並列に接続される。
CR直列回路２５の定数を適当に選ぶと、ダイヤ
ル信号のレベルを規定することが可能となるばか
りでなく、結合トランス２６にダイヤル信号が加
わるため、拡声回路２７によるダイヤル確認が可
能となる。 In this state, the first current loop drives the oscillation circuit OSC of the pushbutton dial 7 and sends the pushbutton dial signal to the subscriber line, but at this time,
A series circuit of the CR series circuit 25 and the coupling transformer 26 is connected in parallel to the subscriber line in an alternating current manner.
By appropriately selecting the constants of the CR series circuit 25, it becomes possible not only to specify the level of the dial signal, but also to add the dial signal to the coupling transformer 26, thereby making it possible to confirm the dial using the amplification circuit 27.

次に第二の電流ループはダイヤル操作をして押
ボタンダイヤル７のスイツチSWが３点接触した
ときから電流ループが形成され、ホトカプラ３３
の発光ダイオード部分に電流が流れるため、ホト
カプラ３３のホトトランジスタ部分はこの電流を
検出し拡声回路２７の受話増幅器３１および送話
増幅器２９を制御し、ダイヤル発信時に結合トラ
ンス９に加わるダイヤル信号の受聴レベルを適正
化し、さらにクリツク音の減衰およびダイヤル時
の送話を停止させるように動作する。 Next, a second current loop is formed when the switch SW of the push button dial 7 contacts three points by operating the dial, and the current loop is formed from the time when the switch SW of the push button dial 7 contacts the photocoupler 33.
Since a current flows through the light emitting diode section of the phototransistor section of the photocoupler 33, the phototransistor section of the photocoupler 33 detects this current and controls the receiving amplifier 31 and the transmitting amplifier 29 of the loudspeaker circuit 27, thereby allowing the dial signal to be applied to the coupling transformer 9 at the time of dialing. It works to optimize the level, attenuate the click sound, and stop transmission when dialing.

次に送受器状態では、送受器を取り上げるとフ
ツクスイツチ５が閉じ、機械スイツチ２３を復旧
させると、押ボタンダイヤル７の第二、第三の接
続端子７−２および７−３は第二、第三の切替接
点組２３−２および２３−３のブレーク接点を通
じてピン端子１０および１１にそれぞれ接続さ
れ、外線端子２および３からフツクスイツチ５を
介して、ダイオードブリツジ６より電流が与えら
れる。すなわち押ボタンダイヤル７に供給する電
流ループおよび送受器回路８の送話器に電流供給
するループが形成される。これにより送受器によ
る通話およびダイヤル発信動作が可能となる。ま
た、このとき接続端子７−４と端子１２の間にホ
トカプラ３３の発光ダイオード部分が挿入された
ままとなるが、発光ダイオードの順方向電圧降下
は高々1.0〜1.5V程度であるため問題にならない。
また拡声電話機の各回路は機械スイツチ２３によ
り、押ボタンダイヤル式電話機１から切離される
ため、送受器による通話およびダイヤル発信動作
には何らの影響も与えない。 Next, in the handset state, when the handset is picked up, the hook switch 5 is closed, and when the mechanical switch 23 is restored, the second and third connection terminals 7-2 and 7-3 of the pushbutton dial 7 are connected to the second and third terminals. They are connected to the pin terminals 10 and 11 through the break contacts of the three switching contact sets 23-2 and 23-3, respectively, and current is applied from the diode bridge 6 from the external line terminals 2 and 3 via the hook switch 5. That is, a current loop for supplying current to the pushbutton dial 7 and a current supplying loop for supplying current to the transmitter of the handset/receiver circuit 8 are formed. This enables telephone calls and dialing operations using the handset. Also, at this time, the light emitting diode part of the photocoupler 33 remains inserted between the connection terminal 7-4 and the terminal 12, but this does not pose a problem because the forward voltage drop of the light emitting diode is about 1.0 to 1.5V at most. .
Furthermore, since each circuit of the loudspeaker telephone is disconnected from the push-button dial telephone 1 by the mechanical switch 23, it does not have any effect on telephone calls and dialing operations using the handset.

本考案の装置に関係する接続端子および端子は
一般的に普及している押ボタンダイヤル電話機で
は、その接続が着脱可能なピン端子構造により構
成されているため、容易に接続を行うことができ
る。 The connection terminals and terminals related to the device of the present invention can be easily connected to commonly used push-button dial telephones because the connection is configured by a removable pin terminal structure.

本考案は以上説明したように一般の押ボタンダ
イヤル電話機に簡単に付加することが可能な付加
形拡声電話機を提供することができる。しかも押
ボタンダイヤル電話機の押ボタンダイヤルを利用
した拡声によるダイヤル発信が、拡声による通話
性能に何ら影響を与えることのない装置が得られ
る。 As described above, the present invention can provide an add-on loudspeaker telephone that can be easily added to a general push-button dial telephone. Moreover, it is possible to obtain a device in which dialing by amplification using the pushbutton dial of a pushbutton dial telephone does not have any effect on the communication performance by amplification.

[Brief explanation of the drawing]

図は本考案の一実施例装置の回路図。１……押ボタンダイヤル式電話機、２，３，
２′，３′……外線端子、４……ベル、５……フツ
クスイツチ、６……ダイオードブリツジ、７……
押ボタンダイヤル、７−１……第一の接続端子、
７−２……第二の接続端子、７−３……第三の接
続端子、７−４……第四の接続端子、８……送受
器回路、９〜１２……端子、１３……中継端子
板、１３−１〜１３−３……端子、２１……付加
形拡声電話機、２２……ダイオードブリツジ、２
３……機械スイツチ手段、２３−１……第一のメ
ーク接点組、２３−２……第二の切替接点組、２
３−３……第三の切替接点組、２３−４……第四
のメーク接点組、２４……チヨークコイル、２５
……CR直列回路、２６……結合トランス、２６
−１，２６−２……端子、２７……拡声回路、２
８……マイクロホン、２９……送話増幅器、３０
……防側音回路、３１……受話増幅器、３２……
スピーカ、３３……ホトカプラ。 The figure is a circuit diagram of a device according to an embodiment of the present invention. 1...Push button dial telephone, 2, 3,
2', 3'...External line terminal, 4...Bell, 5...Hook switch, 6...Diode bridge, 7...
Push button dial, 7-1...first connection terminal,
7-2...Second connection terminal, 7-3...Third connection terminal, 7-4...Fourth connection terminal, 8...Handset/receiver circuit, 9-12...Terminal, 13... Relay terminal board, 13-1 to 13-3...Terminal, 21...Additional loudspeaker telephone, 22...Diode bridge, 2
3... Mechanical switch means, 23-1... First make contact set, 23-2... Second switching contact set, 2
3-3...Third switching contact set, 23-4...Fourth make contact set, 24...Chi York coil, 25
...CR series circuit, 26...Coupling transformer, 26
-1, 26-2... terminal, 27... loudspeaker circuit, 2
8...Microphone, 29...Speech amplifier, 30
... side sound circuit, 31 ... receiver amplifier, 32 ...
Speaker, 33...Hotocoupler.

Claims

[Claims for Utility Model Registration] A first diode bridge 6 that converts the polarity of a current input from an external line terminal into a single polarity, a pushbutton dial 7 connected to the output side of this diode bridge, and this diode A transmitter/receiver circuit 8 is connected to the output side of the bridge, and the push button dial 7 has a first connection terminal 7-1 for supplying power to the oscillation circuit.
, a second connection terminal 7-2 inserted into the flow path of the communication current loop that becomes open when the dial is operated, and a third connection terminal 7 that serves as the return path of the flow path that supplies power to the communication current loop and the oscillation circuit. -3 and a fourth connection terminal 7-4 connected to a circuit in which a DC voltage appears when the dial is operated. External line terminals 2' and 3' connected in parallel, a second diode bridge 22 that converts the polarity of the current input from this external line terminal into a single polarity, and a second diode bridge 22 connected to one end of the output side of this diode bridge. a CR series circuit 25; a coupling transformer 26 having a primary winding connected between the other end of the output side of the second diode bridge 22 and the other end of this CR series circuit; A loudspeaker circuit 27 to which the winding is connected and includes a microphone 28, a transmitting amplifier 29, a side sound protection circuit 30, a receiving amplifier 31, and a speaker 32, and a first and fourth loudspeaker circuit that operate in conjunction with each other when operated by the user Make contact set 23-1, 23-
4 and second and third switching contact sets 23-2, 23
-3, a mechanical switch 23 having a switch 23, a switch coil 24 inserted between the first contact set 23-1 of this switch and the first connection terminal 7-1, and an input side connected to the fourth connection terminal 7. a photocoupler 33 connected to detect the voltage appearing at -4 and whose output side is connected to a circuit for reducing the gain of the transmitting amplifier 29 and the receiving amplifier 31, and the fourth make contact set 23-4 It is inserted between the external line terminal 3' and the second diode bridge 22, and the common contact of the second switching contact set 23-2 is connected to the potential of the second connection terminal 7-2 to break it. A contact is connected to the transmitter terminal of the handset/receiver circuit 8 so as to apply a talking current, and a make contact thereof is connected to a connection point between the CR series circuit 25 and the coupling transformer 26, and the third switching contact set 23 -3 is connected to the potential of the third connection terminal, its break contact is connected to the output return potential point of the first diode bridge 6, and its make contact is connected to the second diode bridge 22. and the CR series circuit 2
An additional type loudspeaker telephone characterized in that it is connected to a connection point with 5.