JP2619010B2 - Loudspeaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a loudspeaker in which one electroacoustic exchanger is used both as a transmitter and a receiver.

(Prior Art) Conventionally, an electroacoustic transducer which is also used as a transmitter and a receiver, a transmitting circuit for transmitting a transmitting signal from the electroacoustic transducer to a telephone line via a transmitting amplifier, A receiving circuit that supplies a receiving signal from a telephone line to the electroacoustic transducer via a receiving amplifier, and switches and connects the electroacoustic transducer to a transmitting circuit and a receiving circuit, thereby providing one electroacoustic transducer. Some loudspeakers are capable of making calls.

FIG. 2 shows a conventional loudspeaker of this type, in which 1 is a telephone line, 2 is a reversible electroacoustic transducer,
3 is a transmitting circuit, 4 is its transmitting amplifier, 5 is a receiving circuit, 6
Is a receiver amplifier, 7 is a protection sound circuit, and 8 is a changeover switch.

The transmission signal from the electroacoustic transducer 2 is transmitted through the telephone line 1 through the switch 8, the transmission amplifier 4, and the protection sound circuit 7, and the reception signal from the telephone line 1 is transmitted by the protection sound circuit 7. It is guided to the receiving circuit 5 side and supplied to the electroacoustic transducer 2 via the receiving amplifier 6 and the switch 8.

9 is a transmission detection amplifier, 10 is a reception detection amplifier, and 11 is a comparator, which constitute a transmission / reception detection circuit. That is, the transmission detection amplifier 9 amplifies a part of the output signal of the transmission amplifier 4, and the reception detection amplifier 10
The output signal is input to the comparator 11. This comparator 11
Outputs "H" when a signal having a level higher than the output signal level of the transmission detection amplifier 9 is input from the reception detection amplifier 10, and outputs "L" otherwise.

12 is a drive transistor, 13 is a relay coil,
The driving transistor 12 is of an npn type, its base is connected to the output terminal of the comparator 11, its collector is connected to the power supply Vcc via the relay coil 13, and its emitter is grounded. Thus, only when the output of the comparator 11 is "H", the transistor 12 is turned on and the relay coil 13 is energized.

The switch 8 comprises a relay contact 81, which connects the electroacoustic transducer 2 to the transmitting circuit 3 and the receiving circuit 5 for switching, and connects the electroacoustic transducer 2 to the transmitting circuit 3. The connecting side is a normally closed contact, and the side connecting the electroacoustic transducer 2 to the receiving circuit 5 is a normally open contact.

In this configuration, when the receiving signal does not enter the receiving circuit 5, the output of the comparator 11 is "L" and the transistor 12 is off, so that the electroacoustic transducer 2 It is connected. Therefore, when there is an acoustic input to the electroacoustic transducer 2 in this state, this is converted as a transmission signal, which is an electric signal, and transmitted to the telephone line 1. At this time, even if a reception signal enters the reception circuit 5,
As long as the electroacoustic transducer 2 is connected to the transmission circuit 3,
The received signal from the receiving circuit 5 does not enter the electro-acoustic transducer 2 and is sufficiently secured when viewed as the amount of attenuation of the received signal during transmission.
Is not absorbed by the receiving circuit 5 side, so that the dynamic range of the transmitting is sufficiently ensured.

When a reception signal enters the reception circuit 5 and the level of the reception signal overcomes the level of the transmission signal, the comparator 10
Outputs “H”. Then, the transistor 12 is turned on, and the relay coil 13 is energized by the energized relay contact 81, and the electroacoustic transducer 2 is connected to the receiving circuit 5. Although the level of the reception signal overcomes the level of the transmission signal, it is normal that reception and transmission are normally performed alternately, and when the reception signal is input, the transmission signal level is Close to nothing. Then, as a result of the electroacoustic transducer 2 being connected to the receiving circuit 5, the received signal from the telephone line 1 is given to the electroacoustic transducer 2 via the receiving amplifier 6. On this occasion,
Even if an acoustic signal is input to the electroacoustic transducer 3, as long as the electroacoustic transducer 2 is connected to the receiving circuit 5, the acoustic signal is not transmitted to the transmitting circuit 3 and is not transmitted to the transmitting circuit 3. When viewed as the amount of attenuation of the transmission signal, it is sufficiently secured as in the case of transmission.

When the input of the reception signal falls below a predetermined level, the output of the comparator 11 becomes "L", the relay contact 81 falls to the normally closed side, and the electroacoustic transducer 2 is connected to the transmission circuit 3. .

By switching the relay contact 81 in this manner, transmission and reception can be performed by one electroacoustic transducer.

(Problems to be Solved by the Invention) However, the one shown in FIG. 2 has a problem that a mechanical operation sound of the relay contact is generated every time the transmission / reception is switched, and this is disturbing to the user. .

Therefore, it has been considered that the changeover switch 8 constitutes a semiconductor element as shown in FIG.

The changeover switch 8 includes semiconductor elements 82 and 83. The semiconductor element 82 is inserted into the transmission circuit 3 and a comparator
It turns on when the output of 11 is "L" and turns off when the output is "H". The semiconductor element 83 is inserted into the receiving circuit 5,
Turns on when the output of the comparator 11 is “H”, and outputs “L”
It turns off when.

That is, transmission / reception is switched by turning the semiconductor elements 82 and 83 on and off in reverse.

However, in the device shown in FIG. 3, the semiconductor elements 82 and 83 constitute a part of the transmission path of the transmission / reception signal. In particular, the dynamic range is secured on the reception side. Therefore, there is a problem that the element requires power. This leads to high costs,
The fact is that the power can be suppressed to some extent, which causes loss of the received signal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and it is an object of the present invention to use a semiconductor element as a switch for switching between transmission and reception without requiring power for securing a dynamic range. It is an object of the present invention to provide a loudspeaker which can be used.

(Means for Solving the Problems) In a loudspeaker according to the present invention, a receiving amplifier is provided with a first amplifier for amplifying a receiving signal with a gain determined by a feedback resistor, and an amplified output for turning on an electroacoustic. This is configured as a cascade amplifier composed of a second amplifier for driving the converter, and an intermittent receiving switch is provided for turning on the transmitting and receiving switch to short-circuit the feedback resistance of the first amplifier.

(Operation) When the feedback resistance of the first amplifier is short-circuited, the gain becomes zero, and the second amplifier is turned off.

That is, the receiving intermittent switch controls connection / disconnection of the electroacoustic transducer to / from the receiving circuit by controlling insertion / short-circuiting of the feedback resistor of the first amplifier.
Not a receiving signal transmission path.

Therefore, the dynamic range of the reception signal is determined by the reception amplifier, and the power for securing the dynamic range is not required for the reception intermittent switch.

Further, since the second amplifier is turned off at the time of transmission, the impedance on the receiving side viewed from the electroacoustic transducer side can be secured sufficiently higher than that of the electroacoustic transducer.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a loudspeaker according to an embodiment of the present invention. Components that are the same as or correspond to those in FIGS. 2 and 3 are denoted by the same reference numerals, and different components are described.

First, 14 is a feedback resistor of the transmission amplifier 4, and 15 is a switching transistor. This transistor 15 is of the npn type, the base of which is connected to the output of the comparator 11,
The collector / emitter lines are connected to the feedback resistor 14 and the arrangement for the transmission amplifier 4. As a result, when the comparator 11 is in the state of detecting the reception signal and outputting "H", the transistor 15 is turned on, the feedback resistor 14 is short-circuited, and the feedback resistance of the transmission amplifier 4 becomes zero. , And the transmission attenuation during reception is ensured.

16 is a receiving amplifier. The receiving layer width unit 16 comprises a first amplifier 17, a second amplifier 18, and an electrolytic capacitor 19. The first amplifier 17 and the second amplifier 18 are connected in cascade, and the receiving signal from the soundproofing circuit 7 is received by the first amplifier 17, and the electroacoustic transducer 2 is received by the second amplifier 18.
Power to drive the motor. The second amplifier 18 has a pnp transistor 20, an npn transistor and a transistor 21 which are connected in a push-pull connection.
The amplifier 17 is turned on by the DC component of the output of the amplifier 17 to amplify the AC component (voice signal) of the same output.
And the received signal is reproduced as sound by the electro-acoustic transducer 2.

22 is a feedback resistor of the receiving amplifier 16, 23 is an electrolytic capacitor, and 24 is a switching transistor. The base of the transistor 24 is connected to the output terminal of the comparator 11, the emitter is connected to the connection point between the output terminal of the first amplifier 17 and the input terminal of the second amplifier 18, and the collector is connected in series with the capacitor 23. It is connected to the input terminal of the first amplifier 17 via the first amplifier 17.
In this configuration, when the comparator 11 is in the state of detecting the transmission signal and outputting “L”, the transistor 24 is turned on, and the feedback resistor 22 is short-circuited to the first amplifier 17 so that the feedback is performed. The resistance becomes 0, and the gain of the first amplifier 17 becomes 0. As a result, the second amplifier 18 is turned off, and the receiving amplifier 16 viewed from the electro-acoustic transducer 2 side during transmission.
Can be secured sufficiently higher than the impedance of the electro-acoustic transducer 2, and the transmission signal from the electro-acoustic transducer 2 can be prevented from being absorbed by the receiving circuit 5 side. The transmission dynamic range can be secured.

〔The invention's effect〕

As described above, according to the present invention, the receiving amplifier is configured as a scade amplifier including first and second amplifiers,
By turning off the second amplifier by short-circuiting the feedback resistor for the first amplifier by the intermittent receiving switch, the impedance of the receiving circuit viewed from the telephone acoustic transducer at the time of transmitting is ensured. Since the receiving circuit is intermittently connected to the electro-acoustic transducer in a configuration that does not become a transmission path of the receiving signal, it is possible to use a semiconductor element as a transmitting / receiving switch without requiring power for securing a dynamic range. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams of different conventional examples. DESCRIPTION OF SYMBOLS 1 ... Telephone line, 2 ... Electroacoustic converter, 3 ... Transmission circuit, 4 ... Transmission amplifier, 5 ... Reception circuit, 9 ... Transmission detection amplifier, 10 ... Reception detection amplifier, 11 ...... Comparator, switching transistor for intermittent transmission side, 16 ... Reception amplifier, 17 ... First amplifier, 18 ... Second amplifier, 22 ...
Feedback resistor, 24 ... Switching transistor for intermittent reception on the receiving side.

Claims (1)

(57) [Claims] An electroacoustic transducer which is used as a transmitter and a receiver; a transmitting circuit for transmitting a transmitting signal from the electroacoustic transducer to a telephone line via a transmitting amplifier; A receiving circuit that supplies a reception signal from a line to the electroacoustic transducer via a reception amplifier, a transmission / reception detection circuit that detects one of the transmission signal and the reception signal, A transmission interruption switch for connecting the electroacoustic transducer to the transmission circuit only when the reception detection circuit is in the detection state of the transmission signal, and only when the transmission / reception detection circuit is in the detection state of the reception signal. A reception intermittent switch for connecting the electroacoustic transducer to the reception circuit,
The receiving amplifier is a cascade including a first amplifier that amplifies the receiving signal with a gain determined by a feedback resistor, and a second amplifier that is turned on by the amplified output and drives the electroacoustic transducer. The reception intermittent switch is configured to be turned on when the transmission / reception detection circuit is in the detection state of the reception signal and to short-circuit the feedback resistor on the input side of the second amplifier. A loudspeaker phone.