JPS6233787B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voice switch device that operates stably even under high noise conditions.

Conventionally, as a voice switch device,
69308, and FIG. 1 shows this voice switch device.

In Fig. 1, 1 and 2 are telephone set, 3 and 4
is a microphone, 5 and 6 are speakers, 7 and 8 are microphone amplifiers, 9 and 10 are speaker amplifiers, 11 and 12 are audio transmission lines, 13 and 14 are audio switches, and 15, 16, 17, and 18 are level settings. 19, 20, 21, and 22 are rectifier circuits, 23, 24 are smoothing circuits, 25, 26 are subtraction circuits, 27, 28 are comparison circuits, 29 is a JK flip-flop, and when the output is "1", the audio switch 13 ，
14 is in a closed state, and 30 is a clock pulse generator.

Next, the operation will be explained based on FIG. Now, the clock pulse generator 30 is generating pulses at a sufficiently faster period than the rise of the audio signal, and at time 0, the outputs V ₁₉ and V 22 of the rectifier circuits 19 and ₂₂ , and the smoothing circuit 2
3, 24 outputs V ₂₃ , V ₂₄ , subtraction circuits 25, 26 outputs V ₂₅ , V ₂₆ and comparison circuits 27, 28 outputs
V ₂₇ and V ₂₈ are each 0, and JK flip-flop 2
It is assumed that the Q output of the switch 9 is held at "0" and the output is held at "1", the audio switch 13 is in the open state, and the audio switch 14 is in the closed state. When speech transmission to the microphone 3 starts at time t ₁ , the output V ₁₉ generated in the rectifier circuit 19 is supplied to the subtraction circuit 25 . However, speaker 6
Since the input of is 0, the output of the smoothing circuit 23 is V ₂₃
is 0, and the output V ₂₅ of the subtraction circuit 25 becomes V ₁₉ . This output V ₂₅ is compared with the set voltage V ₃₁ by the comparator circuit 27, but since the level setting amplifiers 15 and 17 are adjusted so that V ₂₅ > V ₃₁ , the comparator circuit 27 outputs "1'' to the J input terminal of flip-flop 29. Therefore, the Q output of the flip-flop 29 is "1" and the output is "0", so that the audio switch 13 is closed and the audio switch 14 is opened. Therefore, the output of the microphone 3 is supplied to the speaker 5. At this time, the sound from the speaker 5 is routed to the microphone 4 side, and the rectifier circuit 22
produces an output V ₂₂ and is supplied to a subtraction circuit 26.
At the same time, the smoothing circuit 24 is
produces an output V ₂₄ and is supplied to a subtraction circuit 26 .
The subtraction circuit 26 produces an output V ₂₆ = (V ₂₂ −V ₂₄ ), but since the level setting amplifiers 16 and 18 are adjusted so that V ₂₆ <V ₃₂ , the output of the comparison circuit 26 is “ 0" is maintained.

Also, at time t ₂ , while speaking through microphone 3,
When the transmission from the microphone 4 is interrupted, the output V ₂₆ of the subtraction circuit 26 becomes larger than the set voltage V ₃₂ , so the comparison circuit 28 generates an output "1". Therefore, both inputs of the JK flip-flop 29 become "1", the Q output becomes "0", the output becomes "1", the audio switch 13 becomes open, the audio switch 14 becomes closed, and the microphone 4 The output of is supplied to the speaker 6. Since the output of the microphone 4 is immediately applied to the subtraction circuit 26 after being rectified, the audio switch 14 is closed at the same time as the voice is transmitted. In this way, telephone set 1,
You can make hands-free calls between the two.

However, in this voice switch device, for example, if the noise around telephone set 1 is louder than that of telephone set 2, the output of comparator 27 will be "1" even if no call is made from either telephone set 1 or 2. Then, the state in which the output of the comparator 28 is "0" continues.
In this case, when a call is started from the telephone set 2 side, the output of the comparator 28 becomes "1", the audio switch 14 is closed and the voice switch 13 is opened, and the call can be made from the telephone set 2 side. However, if there is a very small silent period in the call from the telephone set 2 side, the output of the comparator 28 becomes "0", the voice switch 13 is closed, and the voice switch 14 is opened. The call will be switched and the call will be cut off. For the same reason, if the volume at the beginning or end of a word in a call is low, the beginning or end of the word will be cut off. That is, if the noise in the vicinity of one telephone set is louder than the noise in the vicinity of the other telephone set, there is a risk that the intelligibility of calls from the other telephone set may be lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voice switch device that has stable switching operation even under high noise conditions and can ensure highly intelligible calls.

The present invention will be explained below based on illustrated embodiments. Note that the same parts as those in the conventional example are given the same reference numerals and explanations are omitted.

FIG. 3 shows the first embodiment, in which 40,4
A variable loss circuit 1 is inserted between the microphone amplifier 7 and the audio switch 13 and between the microphone amplifier 8 and the audio switch 14, respectively.

Also, between the speaker amplifier 9 and the audio switch 13 and between the speaker amplifier 10 and the audio switch 1
4, variable gain amplifiers 42 and 43 are inserted between them.

A series circuit of an amplifier 44, a rectifier circuit 45, a smoothing circuit 46, a subtraction circuit 47, and a smoothing circuit 48 is connected from the connection point between the microphone amplifier 7 and the variable loss circuit 40 to the connection point between the smoothing circuit 23 and the rectifier circuit 21. has been done. Similarly, from the connection point between the microphone amplifier 8 and the variable loss circuit 41 to the connection point between the smoothing circuit 24 and the rectification circuit 20, an amplifier 49, a rectification circuit 50, a smoothing circuit 51, and a subtraction circuit 5 are connected.
2. A series circuit of the smoothing circuit 53 is connected.

The subtraction circuits 47 and 52 each have a logarithmic amplifier 5.
4 and 55 to a subtraction circuit 56, and the subtraction circuit 56 is connected to variable loss circuits 40 and 41 and variable gain amplifiers 42 and 43.

The variable loss circuits 40 and 41, as shown in FIG. , 41. Here, V ₀ is the output voltage of the subtraction circuit 56 when the outputs of the subtraction circuit 47 and the subtraction circuit 52 are equal. Similarly, variable gain amplifiers 42, 43
As shown in FIG. 5, the output voltage V of the subtraction circuit 56 is
The gain changes with respect to

Further, the smoothing circuits 46 and 51 have large time constants, and are designed to detect only external steady noise without being affected by the audio signals input to the microphones 3 and 4.

The thus constructed audio switch circuit operates as follows.

Now, the noise around telephone sets 1 and 2 is X _A [dB] on the telephone set 1 side and X _B (X _B < X _A ) [dB] on the telephone set 2 side, and the difference is l ₁
[dB]. This noise is transmitted from microphones 3 and 4 to microphone amplifiers 7 and 8, and amplifiers 44 and 4.
9. It passes through rectifier circuits 45, 50, smoothing circuits 46, 51, becomes a noise level signal, and is sent to subtraction circuits 47, 52.
is input.

The subtraction circuits 47 and 52 subtract the feedback signal level from the noise level signal in order to remove the effects of the audio signals and noise that enter the microphones 3 and 4 from the speakers 5 and 6. The outputs of the subtraction circuits 47 and 52 are logarithmically converted by logarithmic amplifiers 54 and 55 and supplied to a subtraction circuit 56.

The subtraction circuit 56 compares the logarithmically converted noise levels and outputs an output voltage according to the difference, that is, l ₁ [dB].
Get V ₁ . Due to the output voltage V ₁ of the subtraction circuit 56, the variable loss circuit 40 has a loss of l ₁ [dB], the variable loss circuit 41 has a loss of O [dB], the variable gain amplifier 42 has a gain of O [dB], and the variable gain amplifier 43 has a gain of l ₁
[dB].

Therefore, the noise on the telephone set 1 side is attenuated by l ₁ [dB] by the variable attenuation circuit 40, and the noise from the telephone set 1 is attenuated by l 1 [dB].
is supplied to Therefore, the noise level signals supplied to the subtraction circuits 25 and 26 both have the set voltages V ₃₁ and
It will be the same size, smaller than V ₃₂ . Therefore, the outputs of comparators 27 and 28 are "0". In this state, when a call is started from the side of telephone set 2 with low noise, the output of the comparator 28 becomes "1", the audio switch 13 is opened and the voice switch 14 is closed, and the call from the side of telephone set 2 is started. reaches the telephone set 1 side. If there is a very small silent section in the content of the call, the output of the comparator 28 will be "0", but
Since the output of the comparator 27 is also "0", the state in which the audio switch 13 is open and the audio switch 14 is closed is maintained. Therefore, there are no interruptions during the conversation, and the intelligibility is improved. Also, for the same reason, telephone set 2
Even if the initial sound of the call on the other side is low, the voice switch 13 is immediately switched to open and the same 14 is switched to closed.
No cutting occurs at the beginning of the word, and even if the volume at the end of the word is low, the state in which the audio switch circuit 13 is open and the audio switch circuit 14 is closed is maintained, so no cutting occurs at the end of the word. Note that the gain of the variable gain amplifier 43 is l ₁ [dB]
Since the noise level is increased to X _A [dB], even if a call from the microphone 4 is heard on the telephone set 1 side, the S/N ratio is improved and the call can be heard clearly.

FIG. 6 shows a second embodiment of the present invention, in which the same parts as in the first embodiment are designated by the same reference numerals and their explanation will be omitted.

In FIG. 6, 60 and 61 are main variable loss circuits, which replace the audio switches 13 and 14 of the first embodiment with microphone amplifiers 7 and 8 and variable gain amplifiers 42 and 43 in the audio transmission paths 11 and 12, respectively.
It is inserted between.

Microphone amplifier 7 and main variable loss circuit 60
A level setting amplifier 15, an auxiliary variable loss circuit 64, a variable loss circuit 40, a rectifier circuit 19, and a smoothing circuit 65 are connected in series to the connection point between the microphone amplifier 8 and the main variable loss circuit 61. A level setting amplifier 18, an auxiliary variable loss circuit 66, a variable loss circuit 41, a rectifier circuit 22, and a smoothing circuit 67 are connected in series at the point.

The smoothing circuits 65 and 67 are connected to a comparison output circuit 68, and the comparison output circuit 68 is connected to the main variable loss circuits 60 and 61 and the auxiliary variable loss circuits 64 and 66.

The comparison output circuit 68 outputs an output voltage E according to the difference between the output voltages V ₆₅ and V 67 of the smoothing circuits 65 and ₆₇ ,
Main variable loss circuit 60, depending on its output voltage V ₂
61 and the auxiliary variable loss circuits 64 and 66 change as shown in FIGS. 7 and 8, respectively. Here, F ₀ is the output voltage of the smoothing circuits 65 and 67
This is the output voltage of the comparison output circuit 68 when V ₆₅ and V ₆₇ are equal.

The thus constructed voice switch device operates as follows.

Now, on the telephone set 1 side, the noise is X _A [dB],
On the telephone set 2 side, it is assumed that X _B (X _B <X _A ) [dB], and the difference therebetween is l ₁ [dB]. This noise causes a loss in the variable loss circuit 40 as in the first embodiment.
l ₁ [dB], the variable loss circuit 41 has a loss of O [dB],
The variable gain amplifier 42 has a gain of O [dB], and the variable gain amplifier 43 has a gain of l ₁ [dB].

Therefore, when no audio signal is input, the output voltages V ₆₅ and V 67 of the smoothing circuits 65 and ₆₇ are equal,
The output voltage E of the comparison output circuit 68 is maintained at _E0 .

When audio is input from the microphone 3 in this state, the output voltage of the comparison output circuit 68 changes to E ₁ , for example, and as a result, the main loss circuit 60 and the auxiliary loss circuit 64 have a loss of O [dB], and the main loss circuit 61 And the auxiliary loss circuit 66 has a loss of l ₂ [dB] and l ₃ [dB].
Thus, the audio signal input from the microphone 3 is emitted from the speaker 5. At this time, the influence of the feedback signal from the speaker 5 can be removed by the auxiliary loss circuit 66. Similarly, the audio signal input from the microphone 4 is emitted from the speaker 6 with the gain increased by l ₁ [dB].

As explained above, according to the present invention, the microphone output input to the audio level detection circuit is adjusted according to the level difference between the noise level detection circuits, so that the noise level collected by one microphone is adjusted. Even if the microphone is loud, it prevents the microphone with the loudest noise from being preferentially connected to the loudspeaker with the loudest noise. Therefore, even if a conversation is made from the microphone on the side where the noise is lower, truncations at the beginning of words, truncations in the middle of speech, and truncations at the end of speech do not occur, and intelligibility can be improved.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional example of a voice switch device.
FIG. 2 is a timing diagram showing the operation timing of the conventional example, FIG. 3 is a circuit diagram of the first embodiment based on the present invention, FIG. 4 is a characteristic diagram of the variable loss circuit used in the same embodiment, and FIG. The figure is a characteristic diagram of the variable gain amplifier circuit used in the same example, Figure 6 is a circuit diagram of the second example, Figure 7 is a characteristic diagram of the main variable loss circuit used in the same example, and Figure 8 is a characteristic diagram of the variable gain amplifier circuit used in the same example. is a characteristic diagram of the auxiliary variable loss circuit used in the same example. 3 and 4...first and second microphones, 5 and 6...first and second speakers, 11 and 12...
First and second audio transmission paths, 13 and 14... audio switch (first and second variable gain circuit), 19
and 22... rectifier circuit (first and second audio level detection circuit), 29... JK flip-flop (control circuit), 40 and 41... variable loss circuit (third and fourth variable gain circuit), 46 and 51... Smoothing circuit (first and second noise level detection circuit), 56... Subtraction circuit (control circuit), 60 and 61... Main variable loss circuit (first and second variable gain circuit), 68... Comparison output circuit.

Claims (1)

[Claims] 1 The first terminal has a first microphone and the second
a first audio transmission path having a first speaker at the terminal; a second audio transmission path having a second microphone at the second terminal and a second speaker at the first terminal; a first microphone intervening in the audio transmission path of the device and switching between a transmission state in which the first microphone output is transmitted to the first speaker and a non-transmission state in which the first microphone output is not substantially transmitted to the first speaker;
a transmission state in which the switching means is interposed in the second audio transmission path and transmits the second microphone output to the second speaker; and a non-transmission state in which the second microphone output is not substantially transmitted to the second speaker. a first and second audio level detection circuit that respectively detects the level of the audio signal including noise input from the first and second microphones; When an output appears, the first switching means is switched to a transmission state and the second switching means is switched to a non-transmission state, and when an output appears in the second audio level detection circuit, the first switching means is switched to a non-transmission state. a first control circuit configured to switch the second switching means to a transmitting state; first and second variable gain circuits interposed between the first and second audio level detection circuits, respectively; If the output level of the first noise level detection circuit exceeds the output level of the first and second noise level detection circuits, the first variable gain The second control circuit is configured to reduce the gain of the circuit and to reduce the gain of the second variable gain circuit when the output level of the second noise level detection circuit exceeds the output level of the second noise level detection circuit. Voice switch device.