JPH04156152A - Loud-speaker telephone system - Google Patents

Abstract

PURPOSE:To prevent unnaturalness of speech for double talk and singing due to acoustic coupling between a speaker and a microphone by providing the speaker and the microphone in enclosures different from each other and using light for signal transmission/reception between them. CONSTITUTION:Parts of a microphone unit 1 and a speaker unit 8 are provided, and a down speech signal f2 from the other party of speech is sent to a down speech signal amplifier 14 through a communication interface circuit 16 and is reproduced by a speaker 15. An up speech signal f1 is converted to an electric signal by a microphone 2 of the microphone unit 1 and is subjected to FM modulation by a modulator 4 of an E/O conversion circuit 3 and is converted to an infrared modulation signal by a light emitting element 5. This signal converted by the light emitting element 5 is converted to an electric signal by a light receiving element 11 of an O/E conversion circuit 10 of the speaker unit 8 and is demodulated by a demodulator 12 and is amplified by an up speech signal amplifier 13 and is sent to an up line L1 through a communication interface circuit 6. Thus, unnaturalness of speech for double talk and singing due to acoustic coupling between the speaker and the microphone are prevented.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a public address telephone device, and particularly to a public address telephone that can separate a microphone and a speaker from each other to prevent ringing caused by audio signals going around from the speaker to the microphone. Regarding equipment.

[Prior Art] Usually, as shown in FIG. 2, a public address telephone device TE includes a microphone 21, an upstream audio signal amplifier 22a1, an upstream voice switch 22, an upstream audio signal detection circuit 23, a downstream audio signal detection circuit 24, and a downstream audio signal. The amplifier 24a1 is composed of a downstream voice switch 25, a speaker 26, a communication interface 27, a channel selection control circuit 28, a channel selection control key 29, and a CPU 30. The CPU 30 has a built-in voice switch switching determination program, as well as an upstream and downstream audio signal amplifier. 22a
, 24a. Furthermore, the output sides of the upstream audio signal detection circuit 23 and the downstream audio signal detection circuit 24 are connected to the control input side of the CPU 30, and the control output side is connected to the control sides of the upstream voice switch 22 and the downstream voice switch 24.

The microphone 21 is connected to the input side of the upstream voice switch 22 via the upstream audio signal amplifier 22a, and the output side of the upstream voice switch 22 is connected to a communication interface circuit 27, a terminal T,
It is connected to the upstream line L1 via. Further, the input side of the upstream audio signal detection circuit 23 is connected to the output side of the upstream audio signal amplifier 22a.

Further, the terminal T4 to which the downlink line L2 is connected is connected to the downlink audio signal amplifier 24a via the communication interface circuit 27.
The output side of the downlink audio signal amplifier 24a is connected to the input side of the downlink voice switch 25, and the output side of the downlink voice switch 25 is connected to the speaker 26. Furthermore, the input side of the downstream audio signal detection age 24 is the downstream audio signal amplifier 24a.
connected to the input side of the

Further, the transmission control side of the communication interface circuit 27 is connected to the output side of the tuning control circuit 28, and the input side of the tuning control circuit 28 is connected to the tuning control key 29.

Here, in order to make a call from the loudspeaker telephone equipment TE, the number of the other party is entered in the channel selection control key 29. The channel selection control circuit 28 controls the communication interface circuit 27 based on this partner number, so the communication interface circuit 27 sends and receives channel selection control information via the uplink, waits for a response from the partner, and then enters the communication state. .

In addition, when there is an incoming call, the incoming call signal is sent and received via the down line L2, and the communication interface circuit 27 and the down voice signal amplifier 24a1 are connected to the down line.
The incoming signal can be heard on the speaker 26 via the switch 25. Here, when the channel selection control key 29 is operated, a response signal is returned from the channel selection control circuit 28, and communication with the calling side is established.

By the way, the upstream audio signal f output from the microphone 21,
Or, the downlink audio signal f2 received via the terminal T4 from the uplink and downlink audio signal detection circuits 23 respectively.
．． 24, and if one of the audio signals, for example, the downstream audio signal f, is not received, the voice switch switching determination program built into the CPU 30 is activated, closes the upstream voice switch 22, and connects the upstream line via the terminal T. and transmits the upstream audio signal f, to the upstream audio signal amplifier 2.
The amplification degree of 2a is switched from L level to H level.

When the upstream and downstream audio signals f8 and f2 go up simultaneously and are detected by the downstream audio signal detection circuit 23.24, which one closes one of the upstream and downstream voice switches 22.25 depending on the level of the detected audio signals. At the same time, the gains of the upstream and downstream audio signal amplifiers 22a and 24a are switched from L level to H level, and from H level to L level. In this way, communication failure due to ringing is prevented.

[Problems to be Solved by the Invention] In the loudspeaker telephone device TE having the above configuration, since the gains of the upstream and downstream voice signal amplifiers 22a and 24a are switched, not only does it feel strange when making a call, but also the upstream and downstream voice signal amplifiers 22. Since there is some processing time required by the CPU 30 until switching the number 25, a so-called head-off phenomenon occurs due to this processing time.

Also, normally, the upstream audio signal f generated by the microphone 21
Since the acoustic feedback signal output from the speaker 26 is larger than that from the microphone 21, the audio signal f! This makes it difficult to interrupt calls, making it difficult to make calls smoothly.

[Object of the Invention] The present invention has been made in view of the above-mentioned difficulties, and by providing a speaker and a microphone in different housings and using light to send and receive signals between the two, the unnaturalness of the call during double talk and the unnaturalness of the speaker and the microphone are solved. An object of the present invention is to provide a public address telephone terminal that prevents ringing due to acoustic coupling of a microphone.

[Means for Solving the Problems] In order to achieve the above object, the loudspeaker telephone device of the present invention has the following features:
an E/O conversion circuit that converts an upstream audio signal outputted from the microphone to an upstream transmission path into an optical signal; an 07E conversion means that converts the optical signal converted by the E/O conversion circuit into an upstream audio signal; An upstream audio signal amplifier that amplifies the upstream audio signal converted by the E-conversion means and sends it to the upstream transmission line, a downstream audio signal amplifier that amplifies the downstream audio signal input from the downstream transmission line, and is connected to the downstream audio signal amplifier. It consists of a speaker installed in a separate housing from the microphone.

[Embodiment] Hereinafter, an embodiment of the loudspeaker telephone device according to the present invention will be described in detail with reference to FIG.

The loudspeaker telephone terminal TE according to the present invention has a microphone unit 1 and a speaker unit 8, as shown in FIG.
It is composed of an E/O conversion circuit 3, a light projecting lens 6, and a channel selection control key 7.

Further, the speaker unit 8 includes a light receiving lens 9, a light receiving element 1
1 and a demodulator 12, upstream and downstream audio signal amplifiers 13 and 14, a communication interface circuit 16, and a channel selection control circuit 17.

The microphone 2 of the microphone unit 1 is connected to one input side of the modulator 4 of the E/O conversion circuit 3, and the output side of the modulator 4 is connected to the light emitting element 5. In addition, the tuning control key 7 is connected to the modulator 4.
The upstream audio signal f□ generated by the microphone 2 and the control signal f generated by the channel selection control key 7 are connected to the other input side of the
8 is converted into an infrared modulated signal by the light emitting element 5, and the light is projected to the light receiving lens 9 of the speaker unit 8 via the light projecting lens 6.

Further, the infrared modulated signal received by the light receiving lens 9 of the speaker unit 8 is received by the light receiving element 11 of the 0/E conversion circuit/O.

Further, the output side of the light receiving element 11 is connected to the input side of the demodulator 12, and one output side of the demodulator 12 is connected to the upstream audio signal amplifier 13.
The input side of the channel selection control circuit 17 and the output side of the other are connected to the input side of the channel selection control circuit 17, and the output side of the channel selection control circuit 17 is connected to the control signal input side of the communication interface circuit 16. Further, the output side of the upstream audio signal amplifier 13 is connected via the communication interface circuit 16 to the terminal T1 to which the upstream line is connected.

Furthermore, the terminal T3 to which the downlink line L2 is connected is connected to the input side of the downlink audio signal amplifier 14 via the communication interface circuit 16, and the output side of the downlink audio signal amplifier 14 is connected to the speaker 15.

[Operation of the Invention] To make a call from the loudspeaker telephone device TE having the above configuration, operate the channel selection control key 7 of the microphone unit 1 and enter the number of the other party. A control signal f8 inputted to the modulator 4 of the E/O conversion circuit 3 based on this set number is projected from the light emitting element 6 to the outside via the projection lens 6 as an infrared modulation signal.

The light receiving lens 9 of the speaker unit 8 receives this infrared modulated signal and irradiates the light receiving element 11 of the 0/E conversion circuit/O.

The light receiving element 11 converts the irradiated infrared modulated signal into an electrical signal and sends it to the demodulator 12. The demodulator 12 sends the demodulated control signal f3 to the channel selection control circuit 17. The channel selection control circuit 17 sends out a control signal f3 from the uplink line L1 via the communication interface circuit 16, waits for a response from the other party, and then enters a talking state.

Further, when there is an incoming call, the incoming signal is sent to the downlink audio signal amplifier 14 via the communication interface circuit 16 via the downlink, and the speaker 15 is sounded. When the user listens to the sound of the speaker 15 and operates the channel selection control key 7 of the microphone unit 1, a response signal is sent out in the same manner as when making a call, and the call state is established.

During communication, the downlink audio signal f2 from the other party is sent to the downlink audio signal amplifier 14 via the communication interface circuit 16.
and is played back by the speaker 15.

In addition, the upstream audio signal f is the microphone 2 of the microphone unit 1.
After being converted into an electrical signal, the signal is FM modulated by the modulator 4 of the E/O conversion circuit 3, and converted into an infrared modulated signal by the light emitting element 5. The infrared modulated signal converted by the light emitting element 5 is output to the speaker unit 8 as in the case of the control signal f3 described above.
The light receiving element 11 of the /E conversion circuit /O converts the signal into an electrical signal, and the demodulator 12 demodulates the signal. The upstream audio signal f1 demodulated by the demodulator 12 is amplified by the upstream audio signal amplifier 13, and sent to the upstream line Ll via the communication interface circuit 6.

Here, since the speaker unit 8 is usually attached to a wall surface or the like, and the microphone unit 1 is placed at the operator's hand, the level of the acoustic feedback signal between the speaker 15 and the microphone 2 can be considerably reduced.

In the above embodiment, a case has been described in which the speaker unit 8 is mounted on a wall, but if the speaker unit 8 is mounted on a ceiling or the like, the loudspeaker telephone device TE can be used as a bassing device.

In addition, if the speaker unit 8 and the microphone unit 1 are close to each other, if the speaker unit 8 is configured to include upstream and downstream voice switches as before, the upstream and downstream voices will correspond to the part where the acoustic feedback signal is reduced. Since the sensitivity of the switch can be increased and the number of times during which the gains of the upstream and downstream audio signals f1 and f2 are reduced can be reduced, loudspeaker calls can be realized without any discomfort.

[Effects of the Invention] The loudspeaker telephone device according to the present invention includes an E/O conversion circuit that converts an upstream audio signal outputted from a microphone to an upstream transmission path into an optical signal, and an optical signal converted by the E/O conversion circuit. O/E conversion means for converting into an upstream audio signal, an upstream audio signal amplifier that amplifies the upstream audio signal converted by the O/E conversion unit and sends it to the uplink transmission path, and a downlink audio signal input from the downlink transmission path. It consists of a downlink audio signal amplifier that amplifies the downlink audio signal, and a speaker that is connected to the downlink audio signal amplifier and installed in a different housing from the microphone, which reduces the unnaturalness of calls during double talk and the acoustic coupling between the speaker and microphone. This has the effect of preventing noise caused by.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a loudspeaker telephone device according to the present invention, and FIG. 2 is a block diagram of a conventional loudspeaker telephone device. 2...Microphone 3...E/O conversion circuit/O...O/E conversion circuit 13...Upstream audio signal amplifier 14...・Downstream audio signal amplifier 15...Speaker agent Patent attorney Moritani -O

Claims (1)

[Claims] an E/O conversion circuit that converts an upstream audio signal output from the microphone to an upstream transmission path into an optical signal; and an O/E conversion means that converts the optical signal converted by the E/O conversion circuit into an upstream audio signal. , an upstream audio signal amplifier that amplifies the upstream audio signal converted by the O/E conversion means and sends it to the upstream transmission path; a downstream audio signal amplifier that amplifies the downstream audio signal input from the downlink transmission path; A loudspeaker telephone device comprising: a speaker connected to a downlink audio signal amplifier and provided in a housing different from the microphone.