JPS6337534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a transmitting channel switch inserted in the transmitting channel and a receiving channel switch inserted in the receiving channel, so that the level of the transmitting signal in the transmitting channel and the receiving signal in the receiving channel can be adjusted. The present invention relates to a voice switch device configured to control on/off the sending path switch and the receiving path switch based on a comparison output obtained by comparing the magnitude relationship with the signal level using a comparator.

This type of device needs to have the following four functions.

(1) Avoid cutting off the beginning of speech.

(2) Avoid cutting off the end of the sentence.

(3) No malfunction due to ambient noise.

(4) Avoid blocking on sending and receiving calls.

Furthermore, there are four methods for this voice switch, depending on whether the transmitting signal or receiving signal to be compared is taken into the comparator from before or after the switch.

In the block diagram of FIG. 1, the transmit signal on the transmit path 1 enters the comparator 6 from before the send path switch 4, and the receive signal on the receive path 2 enters the comparator 6 after the receive path switch 5. . 7 is a hybrid circuit connected to the subscriber line 3. In the block diagram of FIG. 2, a channel switch 4 for transmitting and receiving signals,
It is entered into the comparator 6 from before the receiving path switch 5. In the block diagram of FIG. 3, the transmitting and receiving signals are transmitted after the transmitting path switch 4 and the receiving path switch 5, and in the block diagram of FIG. It is entered into comparator 6 before switch 5.

The operation of the voice switch is such that when a transmitting signal is received, the transmitting path switch 4 is closed, and when a receiving signal is received, the receiving path switch 5 is closed. It is something.

First, in the device shown in FIG. 1, the transmitting signal is input to the comparator 6 before the transmitting path switch 4, and the receiving signal is input to the comparator 6 after the receiving path switch 5. Therefore, in the transmitting state, the receiving signal is input to the comparator 6. Because it is not entered,
It becomes difficult to transition from the transmitting state to the receiving state. Furthermore, in the receiving state, the receiving signal output from the speaker on the receiving channel 2 is input to the microphone on the transmitting channel 1 and becomes the transmitting signal at the same time, making it difficult to solve the problem of receiving blocking.

In the device shown in FIG. 2, both the transmitting and receiving signals enter the comparator 6 before the sending path switch 4 and the receiving path switch 5, so transition in both directions is easy.
For the same reason as the above device, it has the disadvantage that it is difficult to solve the problem of receiving blocking.

The device shown in FIG.
Since the signal is input to the comparator 6 after the receiving channel switch 5, blocking of the sending channel does not occur, but there is a drawback that transition in both directions is difficult.

In the device shown in FIG. 4, the transmitting signal is input to the comparator 6 after the transmitting path switch 4, and the receiving signal is input to the comparator 6 before the receiving path switch 5, so the transmitting signal is not input to the comparator 6 in the receiving state. There is a drawback that it is difficult to transition from the receiving state to the transmitting state. However, reception blocking does not occur.

Furthermore, among the above four devices, devices such as those shown in FIGS. 5 and 6 have conventionally been used by adding functions to the device shown in FIG. 4. The device shown in FIG. 5 has an initial setting circuit 9 and a holding circuit 8 added to compensate for the drawbacks of the device shown in FIG. Here, the holding circuit 8
is a time constant circuit to prevent tail-cutting,
Since the hangover time is obtained, a fixed prohibition time is included in the transition from the receiving state to the transmitting state, and the transmitting signal is cut off during this time, resulting in a disconnection at the beginning of the transmitting signal. Generally, this hangover time is required to be 200 msec or more, so this disconnection at the beginning of the conversation has the disadvantage that it significantly impairs the natural feel of the call. In addition, in order to enable a transition from receiving to transmitting, the initial setting circuit 9 forcibly applies a bias to the transmitting side in the initial state, but the comparator 6 changes to the receiving state. In order to achieve this, the received signal must overcome that bias.
The beginning of the conversation on the receiving side is cut off. Furthermore, it has the disadvantage that it is functionally unsuitable for hands-free calls because the calling party is forced to have priority.

A noise head-of-speech detection circuit 10 is added to the device shown in FIG. 5 to distinguish and detect stationary noise and the head of a voice, and its output sets the holding circuit 8 in the transmitting noise state to facilitate the transition from receiving to transmitting. This is the device shown in FIG. The device shown in FIG. 6 has a disadvantage that it is disadvantageous in realizing a built-in type key telephone because the circuit for the additional function is complicated.

Furthermore, in each of the above devices, since the conventional comparator 6 is as shown in FIG. 10, the switching operation is as shown in FIG. 11, and a self-holding circuit is required at the subsequent stage to prevent the end of the story from being cut off. I needed some hangover time here.

The present invention eliminates the above-mentioned drawbacks of the conventional device, is constructed with a relatively simple circuit, does not cause cut-off at the beginning of the line, end of the line, blocking of the sending line, blocking of the receiving line, and is low in cost and has a small mounting area. The present invention provides a voice switch device that can be incorporated into a telephone terminal.

The present invention will be explained in detail below.

FIG. 7 shows an embodiment of the present invention, in which 11 is a self-holding comparator, 12 is a transmission line on/off switch, 13 is a silence detection circuit, 18 and 19 are rectifier circuits, and 20 is a signal synthesis circuit. 1, 2, 3, 4, 5, and 7 are the same as those used in the conventional device.

The operation of the embodiment shown in FIG. 7 will be explained first from the transmitting state. The audio signal from the microphone of the transmission path 1 is sent to the transmission path switch 4, the signal synthesis circuit 20,
It passes through a rectifier circuit 19 and enters a self-holding comparator 11. There, it is compared with the receive signal applied via the rectifier circuit 18, and since the level of the transmit signal is higher than the level of the receive signal in this state, the comparator 11 closes the transmit path switch 4 and turns it on. control to open the receiving path switch 5 and turn it off. The transmission signal passes through the hybrid circuit 7,
It goes out to subscriber line 3.

When the transmitting signal disappears and the receiving signal comes in,
The output of the comparator 11 controls the transmitting path switch 4 to open and the receiving path switch 5 to close, thereby transitioning to the receiving state. On the other hand, the silence detection circuit 13 detects the presence of a reception signal and opens the transmission path opening/closing switch 12. Therefore, in this state, only the received signal is input to the comparator 11, so that reception blocking does not occur and a stable received state can be maintained. When the receiving signal disappears in the receiving state, neither the transmitting signal nor the receiving signal is inputted to the comparator 11, but since the comparator 11 is a self-holding type, the output of the comparator 11 maintains the receiving state. Therefore, this feature automatically provides hangover time and prevents trailing off. On the other hand, since the reception signal is disappearing, the silence detection circuit 13 controls the transmission path switch 5 to close. Therefore, the transmission signal from the microphone of the transmission path 1 is inputted to the comparator 11 via the transmission path opening/closing switch 12. Therefore, in this state, the comparator 11 maintains the receiving state and receives both inputs of the transmitting signal and the receiving signal. If the transmitting signal level is higher than the receiving signal level, the comparator 11 is released from self-holding and transitions to the transmitting state. As a result, the transmitting path switch 4 is closed and the receiving path switch 5 is opened to realize a transmitting state.

Based on the principle described above, it is possible to maintain the hangover time and prevent cutting off of the beginning of the transmission signal.

Next, the self-holding comparator 11 will be explained. FIG. 8 shows a self-holding comparator 11 used in the present invention.
14 is a transmitting signal input terminal, 15 is a specific example of
is the receiving signal input terminal, 16 is the output signal terminal, 17
creates a hysteresis characteristic at the input terminal of the voltage V ₊ generated by positive feedback operations R ₁ and R ₂ .

This does the following: First, input terminal 14
When a transmitting signal having a voltage at is inputted, -V is obtained as the voltage at the output signal terminal 16. Therefore, the voltage V ₊ at terminal 17 is −R ₁ /
R ₁ + R ₂ V. Therefore, the next time a voltage is input as a reception signal, it will be −R ₁ /R ₁ +R ₂ V
When the voltage becomes smaller, +V will be obtained at the output signal terminal 16. In this way, since the voltage V ₊ at terminal 17 acts as a threshold voltage,
Self-holding properties are obtained. Further, during this transition, the switching waveform becomes as shown in FIG. 9 due to the capacitor C, and since the state transition occurs gradually, unnaturalness at the time of switching is avoided.

As explained above, according to the present invention, since the self-holding comparator is composed of one operational amplifier, it is advantageous in terms of implementation and cost, and also has a function to prevent trailing off. . Moreover, the silence detection circuit and the transmitter channel open/close switch easily prevent the beginning of the conversation from being cut off.

[Brief explanation of the drawing]

1, 2, 3, 4, 5, and 6 are block diagrams showing examples of conventional devices, FIG. 7 is a block diagram showing an embodiment of the present invention, and FIG. 8 is an example of a self-holding comparator. 9 is a switching waveform diagram of the circuit of FIG. 8, FIG. 10 is a circuit diagram of an example of a conventional comparator, and FIG. 11 is a switching waveform diagram of the circuit of FIG.

Claims (1)

[Claims] 1. A transmitting channel switch is inserted into the transmitting channel, and a receiving channel switch is inserted into the receiving channel, so that the level of the transmitting signal in the transmitting channel and the level of the receiving signal in the receiving channel are adjusted. The comparison output obtained by comparing the magnitude relationship between In a voice switch device configured such that when the receiving signal is turned off and the receiving signal arrives, the receiving path switch is turned on and the sending path switch is turned off, and the rectified output obtained by smoothing the sending signal is compared with the voice switching device. a first rectifier that inputs as one input of the receiver, a second rectifier that inputs a rectified output obtained by smoothing the received voice signal as the other input of the comparator, and a detection output when there is no received voice signal. A silence detection circuit that outputs
an on/off switch that is turned on by the detection output of the silence detection circuit and operates to apply the transmitting signal to the first rectifier, and further characterized in that the comparator is a self-holding type comparator. voice switch device. 2. The voice switch device according to claim 1, wherein the comparator is a self-holding type comparator having delayed transition characteristics. 3. The voice switch device according to claim 1 or 2, characterized in that the output of the channel switch and the output of the open/close switch are combined at the input of the rectifier. .