JPH0329448A - Loudspeaker telephone set - Google Patents

Abstract

PURPOSE:To avoid the unpleasantness of an opposite party by opening a reception switch when the mode is switched from the reception mode into the transmission mode and adjusting the output period of a control signal to both switches so as to close the transmission switch after the point of time when the vibration of an electric/acoustic converter is vanished. CONSTITUTION:When a reception switch 8 is closed and the mode is switched from the reception mode opening a transmission switch 3 to transmission mode opening the reception switch 8 with the closed reception switch 8, the output period of a control signal to both switches 3, 8 is adjusted to close the transmission switch after the vibration of an electroacoustic transducer 1 is vanished by opening the reception switch 8. Thus, it is prevented that the echo sound is listened to the opposite party due to the delay of reply of the electric/acoustic converter 1 when the mode is switched from the reception mode into the transmission mode through the end of talking of the opposite party. Thus, a loudspeaker telephone set without giving the unpleasantness to the opposite party is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention generally relates to a public address telephone, and more particularly, to a loudspeaker telephone set in which one electroacoustic transducer serves both as a transmitter (microphone) and a receiver (speaker). This invention relates to a public address telephone configured as follows.

(Prior Art) FIG. 3 is a block diagram illustrating the construction of a public address telephone according to the prior art. As mentioned above, the loudspeaker telephone shown in FIG.
It is configured to be used as a microphone) or a receiver (speaker), and includes a transmitting system for transmitting a transmitting signal output from the electroacoustic transducer 1 to the telephone line 6 when used as a transmitter. , and a receiving system which outputs a receiving signal transmitted from the telephone line 6 to an electroacoustic transducer 'r,1 when used as a telephone receiver.

In FIG. 3, the electro-acoustic transducer] converts the voice etc. emitted by the speech name into an electrical signal and outputs the electrical signal. The preamplifier 2 is
A signal outputted from the electroacoustic transducer 1 (ie, a transmitted voice signal) is received, multiplied by 1, and then output. The transmitting audio switch 3 is in a closed state when the logic level of the logic level signal outputted from the switch control circuit 9 and given through the diode 10, the resistor 11, and the time constant circuit 20 changes from "L" to "H", for example. When the state changes from "H" to "L", the state shifts from the open state to the closed state.

When the transmitting audio switch 3 is closed, it outputs the transmitting audio signal output from the preamplifier 2 to the transmitting loudspeaker 4 . The transmitting amplifier 4 receives and amplifies the transmitting audio signal output from the preamplifier 2 through the transmitting audio switch 3 and outputs the amplified signal to the hybrid same path 5. Here, from the electroacoustic transducer 1 to the preamplifier 2, the transmitting audio switch 3,
The line extending through the transmitting amplifier 4 to the hybrid circuit 5 forms the aforementioned transmitting system.

The hybrid circuit 5 receives the transmitted voice signal output from the transmitted voice amplifier 4 and sends it to the telephone line 6. At the same time, when a received voice signal is transmitted through the telephone line 6, the hybrid circuit 5 receives the transmitted received voice signal and outputs the received voice signal to the receiver 1 width divider 7.

The receive amplifier 7 receives a receive voice signal applied from the telephone line 6 through the hybrid circuit 5, amplifies it, and then outputs it. The receiving voice switch 8 operates reciprocally with the opening/closing of the transmitting voice switch 3 (that is, when one switch is closed, the other switch is necessarily in the open state). is output from the switch control circuit 9, and is connected to a diode 10, a resistor 11, and a time constant circuit 2.
For example, when the logic level of the logic level signal applied through 0 changes from "L°" to "H", it shifts from an open state to a closed state, and when it changes from "H°" to "L" (i+J), it changes from a closed state. It is now set to move to open state. When the received voice switch 8 is closed, the received voice signal outputted from the received voice compositor 7 is outputted to the electroacoustic transducer 1 .

The electroacoustic transducer 1 functions as a receiver (i.e., a speaker) when a received voice signal is given from the received voice amplifier 7 through the received voice switch 8, and converts the received voice signal into sound that can be heard by the speaker. and output it. Here, the electroacoustic transducer 1 is connected from the hybrid circuit 5 to the received audio amplifier 7 and the received audio switch 8.
The line leading to is reminiscent of the above-mentioned receiving system.

The switch control circuit 9 is configured such that when one of the above-mentioned transmitting voice switch 3 forming the transmitting system and the receiving voice switch 8 forming the receiving system is closed, the other is in the open state. both audio switches 3 and 8 so that they are placed in
It is provided to selectively control the opening/closing of the. The switch control circuit 9 transmits a transmitting audio signal outputted from the electroacoustic transducer 1 to the transmitting system, and a receiving audio signal transmitted by the telephone line 6 and applied to the receiving system through the hybrid circuit 5. input and compare and calculate both audio signals. When the switch control circuit 9 recognizes that the transmitting voice signal is larger than the receiving voice signal as a result of the comparison calculation of both audio signals, the switch control circuit 9 closes the transmitting voice switch 3 and closes the receiving voice switch 8. A control signal (that is, a logic level "H" signal) for selectively controlling the opening/closing of the dual-tone h switches 3 and 8 is output.

Further, when the switch control circuit 9 recognizes that the received voice signal is larger than the transmitted voice signal as a result of the comparison calculation between the two voice signals, contrary to the above, the switch control circuit 9 switches the received voice switch 8 to close. Regarding the voice switch 3, a control (111) (. (logic level "L" signal) is output for selectively controlling opening/closing of both the voice switches 3 and 8 to open.

A diode 10 is connected between the output side of the switch control circuit 9 and a current limiting resistor 11 .

When the voltage level signal output from the switch control circuit 9 is charged to the capacitor 13 forming the time constant circuit 20 through the current limiting resistor 11, the diode 10 has an impedance as seen from the switch control circuit 9 side. The capacitor 1 of the voltage level signal becomes sufficiently small.
On the other hand, when discharging the accumulated charge from the capacitor 13 to the transmitting audio switch 3 and the receiving audio switch 8, the impedance seen from the time constant circuit 20 side is sufficiently large. Become,
The discharge current from the capacitor 13 is connected to the switch control circuit 9.
Prevent it from flowing to the side.

The samurai constant circuit 20 includes the aforementioned capacitor 13 and resistor 12.
It consists of 10 diodes and 1 current limiting resistor.
1 to receive the voltage level f= signal output from the switch control path 9 and charge it, and discharge the charged electricity Gj to the transmitting voice switch 3 and the receiving voice switch 8 as described above. ing.

The time constant circuit 20 opens the receiving voice switch 8 immediately when the logic level of the control signal output from the switch control circuit 9 changes by nJ when switching from the receiving mode to the transmitting mode, and the transmitting voice switch 3 In order to prevent the end of the conversation of the other party F from being cut off due to the closing of the switch, a delay of Hj is provided in the switching of the switches 3 and 8 according to the time constant.

In the above configuration, by controlling the voice switches 3 and 8 so that the switch control circuit 9 opens and closes the transmitting voice switch 3 and the receiving voice switch 8 reciprocally as described above, both voices are controlled. By simultaneously opening the audio switches 3 and 8, a feedback loop of transmitting and receiving is prevented from being formed, thereby preventing howling from occurring.

(Problems to be Solved by the Invention) By the way, in the conventional loudspeaker telephone having the above-described configuration, the switch control circuit 9 controls the transmission audio signal passing through the transmitting system and the receiving sound h signal passing through the receiving system. By comparing and calculating the magnitude of both audio signals, the audio switches 3 and 8 are reciprocally controlled to open/close. railroad track 6
When the received voice fJ that was being transmitted through the voice terminal is interrupted, the received voice switch 8 immediately becomes open, and the transmitting voice switch 3 becomes open.

However, even if the receiving voice switch 8 is opened and the transmitting JN voice switch 3 is closed because the other party stops talking, the electroacoustic transducer 1 has a large inertia, so the vibration as a speaker does not stop immediately. That is, from the time when the other party stops talking, the vibration corresponding to the recording of the other party's call continues for about 200 ms, and after that,
The reverberant sound caused by the phone call of the phase f-filter speaker continues for approximately 50+as. Therefore, at a special point where the receiving voice switch 8 is opened and the transmitting voice switch 3 is closed (at the point where the receiving mode is switched to the transmitting mode), the other party will be affected by the response delay of the electroacoustic transducer 1. There was a problem in that a reverberant sound called "knot" could be heard, which caused discomfort to the person on the other end of the call.

Therefore, the present invention has been made to solve the above problems, and its zero purpose is to respond when the electroacoustic transducer responds when the other party finishes speaking and switches from the receiving mode to the transmitting mode. To provide a loudspeaker telephone that does not give discomfort to a party on the other end of the call by preventing the party on the other end of the conversation from hearing the lag caused by a delay.

[Precepts of invention]

(Means for Solving the Problems) In order to achieve the above objectives, the loudspeaker telephone according to the present invention has the following features:
an electro-acoustic transducer that serves as both a transmitter and a receiver;
A transmitter switch is installed in the transmitter system that sends the transmitter signal output from the electroacoustic transducer to the telephone line, and connects and disconnects the electroacoustic transducer side and the telephone line side. It is installed in the reception system that sends the received reception signal to the electroacoustic transducer, and is used to disconnect the telephone line side and the electroacoustic transducer side.
Input the following receiving switch, transmitting signal, and receiving signal and compare them. If the transmitting signal is larger, the transmitting switch is closed and the receiving switch is opened. Is there a system to set the receiving mode to close the receiving switch and open the transmitting switch when the number is larger? 8
When switching from the receiving mode to the transmitting mode in response to the output of the control signal from the lower stage for outputting another number and the above-mentioned means, the transmitting switch is opened after the receiving switch is opened and the vibration of the electroacoustic transducer disappears. A control signal is output to both the switches so as to close n! The means for adjusting the t period were biased.

(Function) In the above configuration, the transmitting signal passing through the transmitting system is larger than the receiving signal passing through the receiving system, and the transmitting signal is transmitted from the receiving mode in which the receiving switch is closed and the transmitting switch is open. When switching to the transmitting mode in which the talking switch is closed and the n receiving switches are open, the adjusting means first opens the receiving switch by outputting a control signal to the receiving switch. The vibration of the electroacoustic transducer starts to decay when the other party's name is finished speaking, that is, when the receiver switch is opened, and there is a response delay (time) commensurate with the inertia of the electric sound = C converter. It disappears with interruption). When the vibrations of the electroacoustic capacitor disappear, the regulating means outputs a control signal to the transmitter switch, thereby closing the transmitter switch, which was previously in the open state. By closing the transmit switch, the loudspeaker telephone enters the transmit mode.

When the loudspeaker is set to transmit mode, the vibrations of the air-acoustic transducer caused by the voice emitted by the other party have already disappeared, so by opening the transmit switch, the vibration from the electric g-acoustic transducer is removed. Problems such as the residual sound of the phone being heard by the person on the other end of the phone call are completely erased.

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

FIG. 1 is a block diagram showing the circuit configuration of a loudspeaker telephone according to an embodiment of the present invention.

In general, a public address telephone includes a transmitting circuit that forms a transmitting system,
In the no-F3 state where no signal is transmitted to any of the receiving circuits that form the receiving system, there is a method called the transmitting standby method depending on whether the transmitting audio switch or the receiving audio switch is closed. There is a 2gi type b type that is called the call waiting method. The transmitting standby method refers to a method in which the transmitting voice switch side is closed when there is no signal, and the receiving call standby method refers to a method in which the receiving voice switch side is closed when there is no signal. In a one-off embodiment of the present invention, for convenience of explanation, a loudspeaker telephone with a call waiting system is illustrated in FIG. 1. Further, in the first embodiment of the present invention, the transmitting voice switch 3 is arranged such that the logic level of the signal applied to the transmitting voice switch 3 changes from "L" to "H°" by nJ.
e, the pen transitions from a closed state to an open state, and “H”
” to “L”, the state shifts from the open state to the open state.On the other hand, the receiving voice switch 8 changes from the 7-゛. ■The level changes from "L" to "H°", and at point 1j, it changes from the open state to the open state, and from "H" to "L"
When the state changes to , the state shifts from the open state to the open state. In addition, in FIG. 1, the same parts as shown in FIG. 3 are given the same numbers.

In FIG. 1, a resistor 16, a resistor 17, and a resistor 18 are connected in series.
The series body of resistor 18 is based on the power supply as a whole. fI electric (i.e. Converter 14, Converter 1
Base I$ voltage setting four-way 2 that outputs a threshold voltage Jf of 5
2.

In the base fI voltage setting circuit 22, the voltage divided by the resistor 16 and the resistor 17 and the resistor 18 in series is the base fI voltage (i.e., the threshold voltage) in the converter 14.
converter]4. A series body of a reference voltage setting circuit 22ψ, a resistor 16 and a resistor 17, and a resistor 1
The voltage divided by J.8 and J.8 in converter J. It is output to the comparator 15 as a quasi voltage (ie, threshold voltage). Here, as is clear from the figure, the value of the reference voltage output from the reference voltage setting circuit 22 to the converter 14 is the reference voltage setting [! ! I2δ22
It is set to a higher value than the value of JlsQdene output to the converter 15 from. That is, the threshold value of the comparator 14, which outputs a logic level signal to control the opening/closing of the receiving voice switch 8, is the same as the threshold value of the comparator 14, which outputs a logic level signal to control the opening/closing of the receiving voice switch 3. It is set to a value higher than the threshold voltage of the comparator 15 that outputs the level signal.

As described above, the comparator 14 and the comparator 15 are provided to control opening/closing of the receiving audio switch 8 and opening/closing of the transmitting audio switch 3, respectively. The comparator 14 receives a signal output from the switch control circuit 9 through a diode 10, a current limiting resistor 11, and a time constant circuit 20, and a resistor 16, a resistor 17, and a resistor 18 output from a reference voltage setting circuit 22. Standard divided by series body? A comparison operation is performed with liJf. When the signal value is larger than the reference voltage value, the converter 14 outputs a logic level "H" signal to keep the receiving voice switch 8 in the closed state, and the signal value is set to the reference voltage value. When it becomes equal to or smaller than , a logic level "L" signal is outputted to keep the receiving sound switch 8 in the open state. Similarly to the comparator 14, for the comparator 15, a signal is output from the switch control circuit 9, outputted through the diode 10, the current limiting resistor 11, and the time constant circuit 20, and a signal is output from the reference voltage setting circuit 22. A comparison operation is performed between the series resistor 16 and the resistor 17 and the reference voltage divided by the resistor 18. When the signal value is larger than the sub-voltage value, the converter 15
Maintaining the transmitting voice switch 3 in an open state by outputting a logic level "H' signal, and outputting a logic level "L" signal when the signal value is equal to or smaller than the reference voltage value. This causes the transmitting voice switch 3 to be held in the open state.

Next, in the above configuration, the operation of each part when switching from the receiving state to the transmitting state will be explained with reference to the timing chart shown in FIG.

As already explained, since the electroacoustic transducer 1 has a large inertia, once it starts vibrating in response to a reception signal emitted by the other party, it immediately stops vibrating as a speaker even if the other party has finished speaking. does not stop, and therefore the terminal electric current of the electroacoustic transducer 1 due to this vibration does not disappear immediately. That is, at time to shown on the horizontal axis in FIG. 2, when the other party finishes speaking, the vibration generated in the electroacoustic transducer 1 corresponding to the end of the other party's speech is expressed as shown on the horizontal axis in FIG. ■, +7 between to and n
．． +7 interval t I * tenorul, about 200 IIS continuation sul.

Furthermore, in response to the ending of this word, χ・t, vibrations occur in the electroacoustic transducer 1, followed by the previous nc! rljlHJ t Q
Reverberation continues in the electroacoustic transducer 1 for approximately 50 ms.

Here, while the other party continues the call (i.e.
2), the power of the receiving signal passing through the receiving system is sufficiently large, so the difference value between the signal in the transmitting system calculated by the switch control circuit 9 is It is sufficiently larger than the threshold value of the operation sh of the switch control path 9. Therefore, the switch control circuit 9 has a logic level "
Since the signal of "H" will continue to be output, the output 'i'ts pressure of the four-way time constant 22, that is, the voltage applied to the comparator 14 and the comparator 15, is shown in FIG. 2 (b). Thus, a constant voltage level is maintained until time to.

When the other party's call name stops calling at time 10, the vibration due to the end of the call of the other party's call name is emitted at time tO, as described above.
It continues for about 200ms from time 2 to time 2, but the power of the reception signal passing through the reception system at this time is sufficiently small compared to the power when the other party is continuing the conversation. ing. Therefore, the switch control circuit 9
The difference value between the signal in the transmitting system and the signal calculated in is also sufficiently smaller than the threshold of the operating voltage of the switch control circuit 9. Therefore, the switch control circuit 9 At the elapsed n,1 point, the IJ signal of logic level "L" is output. Therefore, since charging to the specific number of parallel circuits 20 is also stopped at the above-mentioned point, the output voltage from the time constant circuit 20 decreases by the constant, and is applied to the comparators 14 and 15. The voltage generated at the switch 1 decreases as shown in FIG. It will continue for about 200 seconds, so during that time the receiver tone h switch 8
When this occurs, a so-called M tail break occurs. for that,
The value of the reference voltage applied to the comparator 14 from the reference voltage setting circuit 22 is set to a value shown by reference symbol v1 in FIG. Time tl in FIG. 2 that coincides with said Vl
At this time, the logic level of the control signal outputted from the comparator 14 to the receiving audio switch 8 changes from "H" to "L" as shown in FIG. 8 is developed.

The n! voice switch 8 was developed. At time t1, vibrations that continue from the end of the caller's conversation occur as reverberations in the electroacoustic transducer 1, and this vibration continues at time t.
It lasts for about 50 ms from l.

Therefore, in the actual length example, 100ms from time tl
It is set to the value v2 of the output voltage from the time constant circuit 20 at the elapsed time t2. As a result, time constant circuit 2
At time t2 when the voltage applied to the comparator 15 from 0 to v2 matches the voltage v2, the logic level of the control signal outputted from the comparator 15 to the transmitting voice switch 3 as χ·1 becomes as shown in FIG. 2 (2). As shown in , the signal changes from "H" to "L", the transmitting audio switch 3 closes, and the receiving mode is completely switched to the transmitting mode.

Even if the transmitting voice switch 3 is closed to enter the transmitting mode at the time t2, the reverberation of the electric g-sound converter 1 has completely disappeared, so the reverberant sound can be heard by the other party h'. can be prevented. In addition, in this major example,
The transmitting voice switch 3 is closed at time t2 when 100 ms has passed after the receiving voice switch 8 is opened, but the transmitting voice switch 3 is closed after the receiving voice switch 8 is opened. The delay until it is completed is 100a+s.
If it is only a moderate amount, the beginning of the word will not be cut off during transmission.

Although this embodiment has been explained using a loudspeaker telephone with a call-waiting system, the present invention is not only applicable to a loudspeaker telephone with a call-waiting system, but also naturally applicable to a loudspeaker telephone with a call-waiting system. Ru.

〔Effect of the invention〕

As explained above, according to the present invention, when switching from the receiving mode in which the receiving switch is closed and the transmitting switch is opened to the transmitting mode in which the transmitting switch is closed and the receiving switch is opened, the receiving switch is closed. The output timing of the control signals to both switches is adjusted so that the transmitting switch is closed after the vibration of the electroacoustic transducer disappears due to the IJ, so that the output timing of the control signal to both switches is adjusted so that the transmitting switch is closed after the vibration of the electroacoustic transducer disappears. When switching from receiving mode to transmitting mode, it is possible to prevent the other party from hearing the reverberant sound due to the response delay of the electroacoustic transducer, which may cause discomfort to the other party. No public address telephone can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the same circuit configuration of a loudspeaker telephone according to an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the structure shown in FIG. 1, and FIG. ,
FIG. 1 is a block diagram showing a circuit configuration of a public address telephone according to the prior art. 1... Electroacoustic transducer, 3... Sending audio switch,
6... Telephone line, 8... Receiving voice switch, 9...
- Switch control circuit, 14.15... converter.

Claims (1)

[Scope of Claims] An electroacoustic transducer that serves both as a transmitter and a handset, and an electroacoustic transducer side provided in a transmitting system that sends a transmitting signal outputted from the electroacoustic transducer to a telephone line. A transmitter switch is installed in the receiving system to send out the receiving signal transmitted from the telephone line to the electroacoustic transducer, and is installed in the receiving system to connect the telephone line side and the electroacoustic transducer side. It inputs a receive switch that switches on and off the transmitter and a transmitter signal, compares the two, and sets the transmitter mode to close the transmitter switch and open the receiver switch when the transmitter signal is larger. , means for outputting a control signal for switching to a receiving mode by closing a receiving switch and opening a transmitting switch when the receiving signal is larger; and switching from the receiving mode to the transmitting mode in response to the output of the control signal from the means. When switching, the transmitting switch is closed after the receiving switch is opened and the vibration of the electroacoustic transducer disappears, and the transmitting switch is closed. Features a loudspeaker telephone.