JP3442227B2 - Balanced audio transmission / reception circuit - Google Patents
Balanced audio transmission / reception circuitInfo
- Publication number
- JP3442227B2 JP3442227B2 JP24514096A JP24514096A JP3442227B2 JP 3442227 B2 JP3442227 B2 JP 3442227B2 JP 24514096 A JP24514096 A JP 24514096A JP 24514096 A JP24514096 A JP 24514096A JP 3442227 B2 JP3442227 B2 JP 3442227B2
- Authority
- JP
- Japan
- Prior art keywords
- output
- resistor
- terminal
- inverting
- balanced
- 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
Landscapes
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
- Amplifiers (AREA)
Description
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】本発明は平衡型音声送受信回
路に関し、特に２線で音声を送受信し、長距離伝送ので
きる平衡型音声送受信回路に係わる。
【０００２】
【従来の技術】従来から、図２に示すような主装置T5お
よび端末T6間を２線平衡ケーブルL11、L12で接続し、音
声を送受信する平衡型音声送受信回路が知られている。
【０００３】主装置T5は、コンデンサC51、C52と、レベ
ル調整抵抗R51、R52、R53と、抵抗R54〜R58と、反転増
幅回路OP51、OP52と、トランスTS1とで構成され、送話
音声はコンデンサC51、抵抗R55を介して反転増幅回路OP
51の反転入力端子に入力される。反転増幅回路OP51の反
転入力端子と出力側の間には抵抗R54が接続され、反転
増幅回路OP51の非反転入力端子は基準電位REFに接続さ
れている。反転増幅回路OP51の出力側はレベル調整抵抗
R51を介してトランスTS1の一方に接続され、トランスTS
1の他方は基準電位点に接続されている。トランスTS1の
一方はレベル調整抵抗R53を介して反転増幅回路OP52の
反転入力端子に接続され、反転増幅回路OP52の反転入力
端子と出力側の間には抵抗R57が接続されている。反転
増幅回路OP51の出力側はレベル調整抵抗R52、抵抗R56を
介して基準電位REFに接続され、レベル調整抵抗R52と抵
抗R56の接続点は反転増幅回路OP52の非反転入力端子に
接続されている。反転増幅回路OP52の出力側は、抵抗R5
8、コンデンサC52を介して受話音声を出力する。
【０００４】端末T6は、コンデンサC61、C62と、レベル
調整抵抗R61、R62、R63と、抵抗R64〜R68と、反転増幅
回路OP61、OP62と、トランスTS2とで構成され、送話音
声はコンデンサC61、抵抗R65を介して反転増幅回路OP61
の反転入力端子に入力される。反転増幅回路OP61の反転
入力端子と出力側の間には抵抗R64が接続され、反転増
幅回路OP61の非反転入力端子は基準電位REFに接続され
ている。反転増幅回路OP61の出力側はレベル調整抵抗R6
1を介してトランスTS2の一方に接続され、トランスTS2
の他方は基準電位点に接続されている。トランスTS2の
一方はレベル調整抵抗R63を介して反転増幅回路OP62の
反転入力端子に接続され、反転増幅回路OP62の反転入力
端子と出力側の間には抵抗R67が接続されている。反転
増幅回路OP61の出力側はレベル調整抵抗R62、抵抗R66を
介して基準電位REFに接続され、レベル調整抵抗R62と抵
抗R66の接続点は反転増幅回路OP62の非反転入力端子に
接続されている。反転増幅回路OP62の出力側は、抵抗R6
8、コンデンサC62を介して受話音声を出力する。
【０００５】このように構成された平衡型音声送受信回
路において、主装置T5から端末T6に音声信号を送信する
場合、音声信号は反転増幅回路OP51の反転入力端子に入
力される。入力された音声信号は反転増幅回路OP51によ
り反転増幅され、レベル調整抵抗R51を介しトランスTS1
に伝達され２線平衡ケーブルL11、L12に出力される。こ
のとき、レベル調整抵抗R51、R53を介して反転増幅回路
OP52にも音声信号が入力されるが、レベル調整抵抗R52
を介してそれを打ち消すように音声信号が入力されるた
め、ハウリングを起こさない。
【０００６】端末T6では、２線平衡ケーブルL11、L12に
出力された主装置T5からの音声信号は、トランスTS2を
介して入力される。入力された音声信号は、レベル調整
抵抗R63を介して反転増幅回路OP62の反転入力端子に入
力され、反転増幅回路OP62により反転増幅されて出力さ
れる。
【０００７】また、端末T6から主装置T5に音声信号を送
信する場合も同様に、音声信号は反転増幅回路OP61の反
転入力端子に入力される。入力された音声信号は反転増
幅回路OP61により反転増幅され、レベル調整抵抗R61を
介しトランスTS2に伝達され２線平衡ケーブルL11、L12
に出力される。このとき、レベル調整抵抗R61、R63を介
して反転増幅回路OP62にも音声信号が入力されるが、レ
ベル調整抵抗R62を介してそれを打ち消すように音声信
号が入力されるため、ハウリングを起こさない。
【０００８】主装置T5では、２線平衡ケーブルL11、L12
に出力された端末T6からの音声信号は、トランスTS1を
介して入力される。入力された音声信号は、レベル調整
抵抗R53を介して反転増幅回路OP52の反転入力端子に入
力され、反転増幅回路OP52により反転増幅されて出力さ
れる。
【０００９】
【発明が解決しようとする課題】このような平衡型音声
送受信回路では、伝送路が長くなるとその線路抵抗およ
び線間容量の影響を受け大きな伝送損失を生じるととも
に、トランスによる位相差が発生し帰還量のバランスが
崩れるという難点があった。
【００１０】本発明はこのような難点を解決するため
に、２線平衡ケーブルを用いて長距離伝送が可能となる
平衡型音声送受信回路を提供することを目的としてい
る。
【００１１】
【課題を解決するための手段】前述した目的を達成する
ため、本発明の平衡型音声送受信回路は、主装置および
端末間を２線平衡ケーブルで接続して音声を送受信する
平衡型音声送受信回路であって、主装置は、送話すべき
音声信号を抵抗を介して第１の演算増幅回路の反転入力
端子に入力し、第１の演算増幅回路の出力を第１の出力
抵抗を介して帰還抵抗へ帰還させる帰還路に位置する出
力端子を２線平衡ケーブルの一方に接続し、出力端子を
抵抗を介して第２の演算増幅回路の反転入力端子に接続
し、第２の演算増幅回路の出力を第２の出力抵抗を介し
て帰還抵抗へ帰還させる帰還路に位置する出力端子を２
線平衡ケーブルの他方に接続し、２線平衡ケーブルを受
話すべき端末からの音声信号がそれぞれ電圧変換される
出力抵抗を介して差動増幅器に接続し、端末は、送話す
べき音声信号を抵抗を介して第１の演算増幅回路の反転
入力端子に入力し、第１の演算増幅回路の出力を帰還抵
抗へ帰還させる帰還路に位置する出力端子を第１の出力
抵抗を介して２線平衡ケーブルの一方に接続し、第１の
演算増幅回路の出力端子を抵抗を介して第２の演算増幅
回路の反転入力端子に接続し、第２の演算増幅回路の出
力を帰還抵抗へ帰還させる帰還路に位置する出力端子を
第２の出力抵抗を介して２線平衡ケーブルの他方に接続
し、２線平衡ケーブルを受話すべき主装置からの音声信
号がそれぞれ入力される差動増幅器に接続したものであ
る。
【００１２】このような平衡型音声送受信回路では、２
線平衡ケーブルを使用して音声の送受信を行なっても、
長距離伝送が可能になる。
【００１３】
【発明の実施の形態】以下、本発明の平衡型音声送受信
回路をその好ましい一実施例について図面を参照して詳
述する。
【００１４】図１に示す本発明の平衡型音声送受信回路
は、主装置T1および端末T2間を２線平衡ケーブルL1、L2
で接続して音声を送受信する。
【００１５】主装置T1は、直流阻止用コンデンサC11、C
12と、コンデンサC13、C14と、抵抗R11〜R19と、帰還抵
抗R2、R4と、第１の出力抵抗R1と、第２の出力抵抗R3
と、第１の反転増幅回路OP11と、第２の反転増幅回路OP
12と、差動増幅器OP13とで構成されている。
【００１６】主装置T1からの送話すべき音声信号は、コ
ンデンサC13、抵抗R11を介して第１の反転増幅回路OP11
の反転入力端子に入力し、第１の反転増幅回路OP11の出
力を第１の出力抵抗R1を介して帰還抵抗R2へ帰還させる
帰還路に位置する出力端子Aを直流阻止用コンデンサC11
を介して２線平衡ケーブルの一方L1に接続し、第１の反
転増幅回路OP11の帰還路に位置する出力端子Aを抵抗R12
を介して第２の反転増幅回路OP12の反転入力端子に接続
し、第２の反転増幅回路OP12の出力を第２の出力抵抗R3
を介して帰還抵抗R4へ帰還させる帰還路に位置する出力
端子Bを直流阻止用コンデンサC12を介して２線平衡ケー
ブルの他方L2に接続している。第１の反転増幅回路OP11
の非反転入力端子および第２の反転増幅回路OP12の非反
転入力端子は基準電位REFに接続されている。２線平衡
ケーブルL1、L2を受話すべき端末T2からの音声信号がそ
れぞれ電圧変換される出力抵抗R1、R3を介して差動増幅
器OP13の入力端子に接続する。すなわち第１の出力抵抗
R1から抵抗R13を介して差動増幅器OP13の−入力端子に
接続し、第２の出力抵抗R3から抵抗R14を介して差動増
幅器OP13の＋入力端子に接続し、＋入力端子は抵抗R17
を介して基準電位REFに接続されている。差動増幅器OP1
3の出力側は抵抗R19を介して−入力端子に接続され、か
つ抵抗R18、コンデンサC14を介して受話音声を出力す
る。なお、出力端子Aは抵抗R16を介して差動増幅器OP13
の＋入力端子に接続され、出力端子Bは抵抗R15を介して
差動増幅器OP13の−入力端子に接続されている。
【００１７】端末T2は、直流阻止用コンデンサC21、C22
と、コンデンサC23、C24と、抵抗R31〜R37と、帰還抵抗
R22、R24と、第１の出力抵抗R21と、第２の出力抵抗R23
と、第１の反転増幅回路OP21と、第２の反転増幅回路OP
22と、差動増幅器OP23とで構成されている。
【００１８】端末T2から送話すべき音声信号は、コンデ
ンサC23、抵抗R31を介して第１の反転増幅回路OP21の反
転入力端子に入力し、第１の反転増幅回路OP21の出力を
帰還抵抗R22へ帰還させる帰還路に位置する出力端子Eを
第１の出力抵抗R21、直流阻止用コンデンサC21を介して
２線平衡ケーブルの一方L1に接続し、第１の反転増幅回
路OP21の出力端子Eを抵抗R32を介して第２の反転増幅回
路OP22の反転入力端子に接続し、第２の反転増幅回路OP
22の出力を帰還抵抗R24へ帰還させる帰還路に位置する
出力端子Fを第２の出力抵抗R23、直流阻止用コンデンサ
C22を介して２線平衡ケーブルの他方L2に接続してい
る。第１の反転増幅回路OP21および第２の反転増幅回路
OP22の非反転入力端子は基準電位REFに接続されてい
る。２線平衡ケーブルL1、L2を主装置T1からの音声信号
が入力される差動増幅器OP23の入力端子に接続する。即
ち抵抗R33を介して差動増幅器OP23の＋入力端子に接続
し、抵抗R34を介して差動増幅器OP23の−入力端子に接
続し、＋入力端子は抵抗R35を介して基準電位REFに接続
されている。差動増幅器OP23の出力側は抵抗R36を介し
て−入力端子に接続され、かつ抵抗R37、コンデンサC24
を介して受話音声を出力する。
【００１９】このように構成された平衡型音声送受信回
路では、主装置T1から端末T2に音声信号を送信する場
合、音声信号は主装置T1の第１の反転増幅回路OP11の反
転入力端子に入力し、第１の反転増幅回路OP11で反転増
幅されて第１の出力抵抗R1を介して出力端子Aに出力さ
れる。出力端子Aに出力された電圧を＋Vaとすると、こ
の音声信号は第２の反転増幅回路OP12の反転入力端子に
入力され、第２の反転増幅回路OP12で反転増幅されて第
２の出力抵抗R3を介して出力端子Bに出力される。出力
端子Bから出力される電圧を−Vbとすると、２線平衡ケ
ーブルL1、L2間には、電圧Va＋Vbの音声信号が送出され
ることになる。
【００２０】このとき、出力端子Ａ、Ｂはともに反転増
幅回路の帰還路に位置しているため定電圧源となり、出
力インピーダンスは理想的に０となり低インピーダンス
出力である。このため、２線平衡ケーブルL1、L2の線路
の影響を受けにくくなるので、長距離伝送が可能とな
る。
【００２１】また、このときの音声信号は抵抗R13、R16
および抵抗R14、R15によって差動増幅器OP13へお互いを
打ち消すように入力されるため、ハウリングは起こらな
い。
【００２２】端末T2では、受信した主装置T1からの音声
信号を差動増幅器OP23により受信され、出力される。
【００２３】端末T2から主装置T1に音声信号が送信され
る場合、音声信号は端末T2の第１の反転増幅回路OP21の
反転入力端子に入力され、第１の反転増幅回路OP21で反
転増幅されて出力端子Eに出力される。この電圧を＋Ve
とする。音声信号は第２の反転増幅回路OP22の反転入力
端子に入力され、第２の反転増幅回路OP22で反転増幅さ
れて出力端子Fから出力される。出力端子Fから出力され
た電圧を−Vfとする。
【００２４】ここで、出力端子A、B間が定電圧源のた
め、出力端子C、D間には音声信号は電圧として存在せ
ず、電流として存在することになり、その値は＋Ve／R2
1および−Vf／R23で決定される。このため、２線平衡ケ
ーブルL1、L2の線間容量の影響を受けにくくなり、さら
に第１の出力抵抗R1、R21および第２の出力抵抗R3、R23
を線路抵抗に対して十分大きく設定しておけば線路の影
響を受けにくく、長距離伝送が可能になる。
【００２５】また、このときの音声信号は出力端子C、D
間はおいて電圧を発生しないため、ハウリングは起こら
ない。
【００２６】主装置T1では、受信した端末T2からの音声
信号が第１の出力抵抗R1および第２の出力抵抗R3により
電圧変換され、出力端子G、H間において音声信号による
電圧が発生し、差動増幅器OP13により受信され、出力さ
れる。また、出力端子A、Bにおいては電圧を発生しない
ため、抵抗R15、R16の経路には何ら影響しない。
【００２７】なお、上記の実施例では主装置、端末を１
対１で構成した例を示したが、端末にリレーなどでスイ
ッチ回路を設けて１対ｎの構成にしても同様の効果を奏
する。
【００２８】
【発明の効果】以上の説明から明らかなように、本発明
の平衡型音声送受信回路によれば、２線平衡ケーブルで
長距離の音声送受が低コストで実現できる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balanced voice transmitting / receiving circuit, and more particularly to a balanced voice transmitting / receiving circuit capable of transmitting and receiving voice over two wires and transmitting data over a long distance. 2. Description of the Related Art Conventionally, there has been known a balanced voice transmitting / receiving circuit for transmitting and receiving voice by connecting a main unit T5 and a terminal T6 with two-wire balanced cables L11 and L12 as shown in FIG. . The main unit T5 is composed of capacitors C51 and C52, level adjustment resistors R51, R52 and R53, resistors R54 to R58, inverting amplifier circuits OP51 and OP52, and a transformer TS1. Inverting amplifier OP via C51 and resistor R55
Input to 51 inverting input terminals. The resistor R54 is connected between the inverting input terminal and the output side of the inverting amplifier OP51, and the non-inverting input terminal of the inverting amplifier OP51 is connected to the reference potential REF. The output side of the inverting amplifier OP51 is a level adjustment resistor
Connected to one of the transformers TS1 via R51
The other of 1 is connected to the reference potential point. One of the transformers TS1 is connected to the inverting input terminal of the inverting amplifier circuit OP52 via the level adjusting resistor R53, and the resistor R57 is connected between the inverting input terminal of the inverting amplifier circuit OP52 and the output side. The output side of the inverting amplifier circuit OP51 is connected to the reference potential REF via the level adjusting resistors R52 and R56, and the connection point between the level adjusting resistor R52 and the resistor R56 is connected to the non-inverting input terminal of the inverting amplifier circuit OP52. . The output side of the inverting amplifier OP52 is connected to the resistor R5
8. Output the received voice via the capacitor C52. The terminal T6 is composed of capacitors C61 and C62, level adjusting resistors R61, R62 and R63, resistors R64 to R68, inverting amplifier circuits OP61 and OP62, and a transformer TS2. , The inverting amplifier circuit OP61 via the resistor R65
Is input to the inverting input terminal. The resistor R64 is connected between the inverting input terminal and the output side of the inverting amplifier OP61, and the non-inverting input terminal of the inverting amplifier OP61 is connected to the reference potential REF. The output side of the inverting amplifier OP61 is a level adjustment resistor R6.
1 is connected to one of the transformers TS2 and the transformer TS2
Is connected to a reference potential point. One of the transformers TS2 is connected to the inverting input terminal of the inverting amplifier circuit OP62 via the level adjusting resistor R63, and the resistor R67 is connected between the inverting input terminal of the inverting amplifier circuit OP62 and the output side. The output side of the inverting amplifier OP61 is connected to the reference potential REF via the level adjusting resistors R62 and R66, and the connection point between the level adjusting resistor R62 and the resistor R66 is connected to the non-inverting input terminal of the inverting amplifier OP62. . The output side of the inverting amplifier OP62 is connected to the resistor R6
8. Output the received voice via the capacitor C62. [0005] In the balanced audio transmission / reception circuit configured as described above, when an audio signal is transmitted from the main device T5 to the terminal T6, the audio signal is input to the inverting input terminal of the inverting amplifier OP51. The input audio signal is inverted and amplified by the inverting amplifier circuit OP51, and the transformer TS1 is transmitted through the level adjusting resistor R51.
And output to the two-wire balanced cables L11 and L12. At this time, the inverting amplifier circuit via the level adjustment resistors R51 and R53
The audio signal is also input to OP52, but the level adjustment resistor R52
A howling does not occur because an audio signal is input so as to cancel the signal via. In the terminal T6, the audio signal from the main unit T5 output to the two-wire balanced cables L11 and L12 is input via the transformer TS2. The input audio signal is input to the inverting input terminal of the inverting amplifier OP62 via the level adjustment resistor R63, and is inverted and amplified by the inverting amplifier OP62 and output. [0007] Similarly, when transmitting an audio signal from the terminal T6 to the main device T5, the audio signal is input to the inverting input terminal of the inverting amplifier OP61. The input audio signal is inverted and amplified by the inverting amplifier circuit OP61, transmitted to the transformer TS2 via the level adjusting resistor R61, and sent to the two-wire balanced cables L11 and L12.
Is output to At this time, the audio signal is also input to the inverting amplifier circuit OP62 via the level adjustment resistors R61 and R63, but the audio signal is input so as to cancel it through the level adjustment resistor R62, so that no howling occurs. . In the main unit T5, two-wire balanced cables L11, L12
The audio signal output from the terminal T6 is input via the transformer TS1. The input audio signal is input to the inverting input terminal of the inverting amplifier circuit OP52 via the level adjustment resistor R53, and is inverted and amplified by the inverting amplifier circuit OP52 to be output. In such a balanced voice transmitting / receiving circuit, when the transmission line becomes long, the transmission line is affected by the line resistance and the line capacitance, causing a large transmission loss and the phase difference due to the transformer. There was a problem that the balance of the return amount was lost due to the occurrence. An object of the present invention is to provide a balanced voice transmitting / receiving circuit capable of long-distance transmission using a two-wire balanced cable in order to solve such a problem. In order to achieve the above-mentioned object, a balanced voice transmitting / receiving circuit according to the present invention is a balanced voice transmitting / receiving circuit for connecting a main unit and a terminal with a two-wire balanced cable to transmit and receive voice. An audio transmitting / receiving circuit, wherein a main device inputs an audio signal to be transmitted to a first operational amplifier circuit via an inverting input terminal via a resistor, and outputs an output of the first operational amplifier circuit to a first output resistor. Connect the output terminal located on the feedback path that feeds back to the feedback resistor to one end of the two-wire balanced cable, and connect the output terminal
Through a resistor connected to the inverting input terminal of the second operational amplifier, an output terminal located in the feedback path for feeding back the output of the second operational amplifier to the feedback resistor via a second output resistor 2
Connected to the other line balanced cable, the two-wire balanced cable through an output resistance audio signal from the terminal to be received is converted to a voltage, respectively connected to a differential amplifier, the terminal resistor audio signal to be transmitter first input to the inverting input terminal of the operational amplifier via a first computing an output terminal for the output of the amplifier circuit is located in the feedback path for feeding back the feedback resistors via a first output resistor 2-wire balanced Connect one end of the cable and the first
Connect the output terminal of the operational amplifier to the inverting input terminal of the second operational amplifier via a resistor, the output terminal of the output of the second operational amplifier circuit located in the feedback path for feeding back the feedback resistor second The two-wire balanced cable is connected to the other of the two-wire balanced cables via an output resistor, and the two-wire balanced cable is connected to a differential amplifier to which a voice signal from a main unit to be received is input. In such a balanced voice transmitting / receiving circuit, 2
Even if you send and receive audio using a wire balanced cable,
Long distance transmission becomes possible. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a balanced voice transmitting / receiving circuit according to the present invention will be described in detail with reference to the drawings. The balanced voice transmission / reception circuit of the present invention shown in FIG. 1 connects two-wire balanced cables L1, L2 between a main unit T1 and a terminal T2.
To send and receive audio. The main unit T1 includes DC blocking capacitors C11 and C
12, capacitors C13 and C14, resistors R11 to R19, feedback resistors R2 and R4, a first output resistor R1, and a second output resistor R3.
, A first inverting amplifier OP11, and a second inverting amplifier OP
12 and a differential amplifier OP13. An audio signal to be transmitted from the main unit T1 is supplied to a first inverting amplifier OP11 via a capacitor C13 and a resistor R11.
And an output terminal A located on a feedback path for feeding the output of the first inverting amplifier OP11 back to the feedback resistor R2 via the first output resistor R1 is connected to a DC blocking capacitor C11.
And the output terminal A located on the feedback path of the first inverting amplifier circuit OP11 is connected to a resistor R12.
To the inverting input terminal of the second inverting amplifier circuit OP12, and connect the output of the second inverting amplifier circuit OP12 to the second output resistor R3.
The output terminal B located on the feedback path for feeding back to the feedback resistor R4 via the resistor R4 is connected to the other L2 of the two-wire balanced cable via the DC blocking capacitor C12. First inverting amplifier circuit OP11
And the non-inverting input terminal of the second inverting amplifier OP12 are connected to the reference potential REF. The two-wire balanced cables L1 and L2 are connected to the input terminals of the differential amplifier OP13 via output resistors R1 and R3, respectively, which convert the audio signals from the terminal T2 to be received into voltage. That is, the first output resistance
R1 is connected to the-input terminal of the differential amplifier OP13 via the resistor R13, the second output resistor R3 is connected to the + input terminal of the differential amplifier OP13 via the resistor R14, and the + input terminal is connected to the resistor R17.
To the reference potential REF. Differential amplifier OP1
The output side of 3 is connected to a negative input terminal via a resistor R19, and outputs a received voice via a resistor R18 and a capacitor C14. The output terminal A is connected to the differential amplifier OP13 via the resistor R16.
The output terminal B is connected via a resistor R15 to a negative input terminal of the differential amplifier OP13. The terminal T2 is connected to DC blocking capacitors C21 and C22.
, Capacitors C23 and C24, resistors R31 to R37, and feedback resistor
R22, R24, a first output resistor R21, and a second output resistor R23
, A first inverting amplifier OP21, and a second inverting amplifier OP
22 and a differential amplifier OP23. An audio signal to be transmitted from the terminal T2 is input to the inverting input terminal of the first inverting amplifier OP21 via the capacitor C23 and the resistor R31, and the output of the first inverting amplifier OP21 is sent to the feedback resistor R22. The output terminal E located on the feedback path for feedback is connected to one end L1 of a two-wire balanced cable via a first output resistor R21 and a DC blocking capacitor C21, and the output terminal E of the first inverting amplifier circuit OP21 is connected to a resistor. Connected to the inverting input terminal of the second inverting amplifier OP22 via R32,
The output terminal F located on the feedback path for returning the output of 22 to the feedback resistor R24 is connected to the second output resistor R23 and a DC blocking capacitor.
It is connected to the other L2 of the two-wire balanced cable via C22. First inverting amplifier circuit OP21 and second inverting amplifier circuit
The non-inverting input terminal of OP22 is connected to the reference potential REF. The two-wire balanced cables L1 and L2 are connected to the input terminal of the differential amplifier OP23 to which the audio signal from the main device T1 is input. That is, it is connected to the + input terminal of the differential amplifier OP23 via the resistor R33, connected to the-input terminal of the differential amplifier OP23 via the resistor R34, and connected to the reference potential REF via the resistor R35. ing. The output side of the differential amplifier OP23 is connected to the-input terminal via a resistor R36, and a resistor R37 and a capacitor C24 are connected.
The received voice is output via the. In the balanced audio transmission / reception circuit configured as described above, when an audio signal is transmitted from the main device T1 to the terminal T2, the audio signal is input to the inverting input terminal of the first inverting amplifier OP11 of the main device T1. Then, the signal is inverted and amplified by the first inverting amplifier circuit OP11 and output to the output terminal A via the first output resistor R1. Assuming that the voltage output to the output terminal A is + Va, this audio signal is input to the inverting input terminal of the second inverting amplifier circuit OP12, is inverted and amplified by the second inverting amplifier circuit OP12, and has a second output resistance R3 Is output to the output terminal B via. Assuming that the voltage output from the output terminal B is -Vb, an audio signal of the voltage Va + Vb is transmitted between the two-wire balanced cables L1 and L2. At this time, since both output terminals A and B are located on the feedback path of the inverting amplifier circuit, they become constant voltage sources, and the output impedance is ideally 0, which is a low impedance output. For this reason, since it is hard to be affected by the lines of the two-wire balanced cables L1 and L2, long-distance transmission is possible. At this time, the audio signal is supplied by resistors R13 and R16.
Howling does not occur because the signals are input to the differential amplifier OP13 by the resistors R14 and R15 so as to cancel each other. In the terminal T2, the received audio signal from the main device T1 is received and output by the differential amplifier OP23. When an audio signal is transmitted from the terminal T2 to the main unit T1, the audio signal is input to the inverting input terminal of the first inverting amplifier OP21 of the terminal T2, and is inverted and amplified by the first inverting amplifier OP21. Output to the output terminal E. This voltage is + Ve
And The audio signal is input to the inverting input terminal of the second inverting amplifier OP22, is inverted and amplified by the second inverting amplifier OP22, and is output from the output terminal F. The voltage output from the output terminal F is -Vf. Since the voltage between the output terminals A and B is a constant voltage source, the audio signal does not exist as a voltage but exists as a current between the output terminals C and D, and its value is + Ve / R2
It is determined by 1 and -Vf / R23. For this reason, it is hardly affected by the line capacitance of the two-wire balanced cables L1 and L2, and the first output resistors R1 and R21 and the second output resistors R3 and R23
Is set to be sufficiently large with respect to the line resistance, it is hardly affected by the line, and long-distance transmission becomes possible. The audio signal at this time is output to output terminals C and D.
Since no voltage is generated at intervals, howling does not occur. In the main unit T1, the received audio signal from the terminal T2 is converted into a voltage by the first output resistor R1 and the second output resistor R3, and a voltage is generated between the output terminals G and H by the audio signal. The signal is received and output by the differential amplifier OP13. Further, since no voltage is generated at the output terminals A and B, there is no influence on the path of the resistors R15 and R16. In the above embodiment, the main unit and the terminal are connected to one.
Although an example of a one-to-one configuration has been described, a similar effect can be obtained even when a terminal is provided with a switch circuit such as a relay or the like to configure a one-to-n configuration. As is clear from the above description, according to the balanced voice transmission / reception circuit of the present invention, long-distance voice transmission / reception can be realized at low cost with a two-wire balanced cable.
【図面の簡単な説明】
【図１】本発明による平衡型音声送受信回路の一実施例
を示すブロック図。
【図２】従来の平衡型音声送受信回路を示すブロック
図。
【符号の説明】
T1・・・・・・主装置
T2・・・・・・端末
L1、L2・・・・・・２線平衡ケーブル
OP11、OP21・・・・・・第１の演算増幅回路
R1、R21・・・・・・第１の出力抵抗
R2、R4、R22、R24・・・・・・帰還抵抗
A、B、E、F・・・・・・出力端子
OP12、OP22・・・・・・第２の演算増幅回路
R3、R23・・・・・・第２の出力抵抗
OP13、OP23・・・・・・差動増幅器R11・・・・・・抵抗 R12・・・・・・抵抗 R31・・・・・・抵抗 R32・・・・・・抵抗 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a balanced voice transmitting / receiving circuit according to the present invention. FIG. 2 is a block diagram showing a conventional balanced audio transmission / reception circuit. [Description of Signs] T1 Main device T2 Terminals L1 and L2 Two-wire balanced cables OP11 and OP21 First operational amplifier circuit R1, R21 ... first output resistors R2, R4, R22, R24 ... feedback resistors A, B, E, F ... output terminals OP12, OP22 ... ... 2nd operational amplifier circuits R3, R23 ... 2nd output resistors OP13, OP23 ... Differential amplifier R11 ... Resistor R12 ... Resistance R31: Resistance R32: Resistance
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭57−123742（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H04B 3/00 H03F 3/00 H04M 1/00 ──────────────────────────────────────────────────続 き Continued on the front page (56) References JP-A-57-123742 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) H04B 3/00 H03F 3/00 H04M 1 / 00
Claims (1)
衡ケーブル（L1、L2）で接続して音声を送受信する平衡
型音声送受信回路であって、 前記主装置は、送話すべき音声信号を抵抗（R11）を介
して第１の演算増幅回路（OP11）の反転入力端子に入力
し、前記第１の演算増幅回路の出力を第１の出力抵抗
（R1）を介して帰還抵抗（R2）へ帰還させる帰還路に位
置する出力端子（A）を前記２線平衡ケーブルの一方に
接続し、前記出力端子を抵抗（R12）を介して第２の演
算増幅回路（OP12）の反転入力端子に接続し、前記第２
の演算増幅回路の出力を第２の出力抵抗（R3）を介して
帰還抵抗（R4）へ帰還させる帰還路に位置する出力端子
（B）を前記２線平衡ケーブルの他方に接続し、前記２
線平衡ケーブルを受話すべき前記端末からの音声信号が
それぞれ電圧変換される前記出力抵抗を介して差動増幅
器（OP13）に接続し、 前記端末は、送話すべき音声信号を抵抗（R31）を介し
て第１の演算増幅回路（OP21）の反転入力端子に入力
し、前記第１の演算増幅回路の出力を帰還抵抗（R22）
へ帰還させる帰還路に位置する出力端子（E）を第１の
出力抵抗（R21）を介して前記２線平衡ケーブルの一方
に接続し、前記第１の演算増幅回路の出力端子を抵抗
（R32）を介して第２の演算増幅回路（OP22）の反転入
力端子に接続し、前記第２の演算増幅回路の出力を帰還
抵抗（R24）へ帰還させる帰還路に位置する出力端子
（F）を第２の出力抵抗（R23）を介して前記２線平衡ケ
ーブルの他方に接続し、前記２線平衡ケーブルを受話す
べき前記主装置からの音声信号がそれぞれ入力される差
動増幅器（OP23）に接続したことを特徴とする平衡型音
声送受信回路。(1) A balanced audio transmission / reception circuit for transmitting / receiving audio by connecting a main unit (T1) and a terminal (T2) with two-wire balanced cables (L1, L2). The main unit transmits a voice signal to be transmitted via a resistor (R11).
First input to the inverting input terminal of the operational amplifier (OP11), a feedback path for feeding back the output of said first operational amplifier to the feedback resistor via a first output resistor (R1) (R2) and output terminal for position (a) connected to one of the two-wire balanced cable, the second Starring through a resistor (R12) to the output terminal
Connected to the inverting input terminal of the calculation amplifier (OP12), the second
The output terminal (B) located on the feedback path for returning the output of the operational amplifier circuit of (2) to the feedback resistor (R4) via the second output resistor (R3) is connected to the other end of the two-wire balanced cable.
A line balanced cable is connected to a differential amplifier (OP13) via the output resistor, which converts a voice signal from the terminal to be received into a voltage, and the terminal converts the voice signal to be transmitted to a resistor (R31). Through
First input to the inverting input terminal of the operational amplifier (OP21) Te, feedback resistors the output of said first operational amplifier circuit (R22)
An output terminal (E) located on a feedback path for feeding back to the other end of the two-wire balanced cable is connected via a first output resistor (R21), and an output terminal of the first operational amplifier circuit is connected to a resistor.
An output terminal (F) connected to the inverting input terminal of the second operational amplifier circuit (OP22) via (R32) and located on a feedback path for returning the output of the second operational amplifier circuit to the feedback resistor (R24). ) Is connected to the other of the two-wire balanced cable via a second output resistor (R23), and a differential amplifier (OP23) to which an audio signal from the main unit to receive the two-wire balanced cable is input, respectively. ), A balanced voice transmission / reception circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24514096A JP3442227B2 (en) | 1996-09-17 | 1996-09-17 | Balanced audio transmission / reception circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24514096A JP3442227B2 (en) | 1996-09-17 | 1996-09-17 | Balanced audio transmission / reception circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1093481A JPH1093481A (en) | 1998-04-10 |
| JP3442227B2 true JP3442227B2 (en) | 2003-09-02 |
Family
ID=17129226
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24514096A Expired - Lifetime JP3442227B2 (en) | 1996-09-17 | 1996-09-17 | Balanced audio transmission / reception circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3442227B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011030161A (en) * | 2009-07-29 | 2011-02-10 | Aiphone Co Ltd | Intercom system |
-
1996
- 1996-09-17 JP JP24514096A patent/JP3442227B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011030161A (en) * | 2009-07-29 | 2011-02-10 | Aiphone Co Ltd | Intercom system |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1093481A (en) | 1998-04-10 |
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