JPS642296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a wireless telephone device that switches between transmission and reception by detecting voice in a voice detector.
The present invention relates to a sensitivity control method for setting the sensitivity of a voice detector at the end of a call to an initial value.

Prior Art and Problems A wireless telephone device that switches between transmitting and receiving based on the output when a voice is detected by a voice detector is capable of transmitting signals from a two-wire telephone via a single-frequency simplex radio. This is used in communication systems that use telephones to make calls.

Conventionally, voice detectors used for the purpose of switching transmission and reception by voice have fixed or semi-fixed sensitivity, and the sensitivity is usually kept constant during use. However, the environment in which a call requester accessing a wireless telephone device is located is not always constant, and the amount of background noise often varies. Therefore, by keeping the sensitivity of the voice detector constant, it is possible that the sensitivity is too high and the voice detector malfunctions due to background noise, causing the transmitter to continue to be activated unduly, or conversely, the sensitivity may become too high. In some cases, the level was too low, causing problems such as voice transmission not being able to be activated smoothly.

Therefore, we monitor the time during which the voice detector determines that there is voice, and when the time exceeds a certain period of time, we control the voice detector to reduce its sensitivity. A method to prevent the transmitter from being activated improperly due to noise, etc., or to monitor the time when the voice detector does not determine that there is voice and the receiver is receiving radio waves from the other party's terminal. When the voice detector's sensitivity is too low, the transmitter is activated even though the caller is talking. A method can be considered to prevent a situation in which the device is not activated. When performing such control, it is necessary to set the sensitivity of the voice detector to an initial value at the start of control, but conventionally, no suitable means for setting such an initial value has been known.

Purpose of the Invention The present invention aims to solve the problems of the prior art, and its purpose is to provide a method for switching between transmission and reception based on the output when a voice is detected by a voice detector. In a wireless telephone device, the initial value when performing control to lower the sensitivity of the voice detector or increase the sensitivity of the voice detector is set to 1 when the voice detector does not determine that there is voice and the receiver does not detect a radio wave. The sensitivity of the voice detector is reset to the initial value every time a call ends by monitoring the time when no voice is received and setting the sensitivity of the voice detector to a preset initial value when it exceeds a certain time. It is an object of the present invention to provide a system that can prevent an error in detecting the voice of a caller in a next call based on the voice detector sensitivity set corresponding to the previous call.

Structure of the Invention The sensitivity control method of the present invention is based on the fact that in normal conversation, there are syllable breaks, and the time a speaker continues to utter continuously is at most a few seconds, but never for tens of seconds. Focusing on this, we monitor the amount of time that the audio detector does not determine that there is audio and the receiver does not receive radio waves, and if this condition continues even after a certain period of time has elapsed. , it is determined that the call has ended, and the sensitivity of the voice detector is controlled to return to a preset initial value.

Embodiment of the Invention FIG. 1 shows the configuration of a radio telephone device to which the present invention is applied, as an embodiment of the sensitivity control method of the present invention. This wireless telephone device shares one frequency for transmission and reception, activates the transmitter only when the voice detector determines that there is voice, connects the antenna to the transmitter using the antenna switcher, sends out a call signal, and transmits the voice signal. If the detector does not determine that there is audio, an antenna is connected to the receiver to receive signals from the terminal.

In Fig. 1, 1A,..., 1N are telephones, 2
is the exchange, 3 is the sending line, 4 is the receiving line, 5 is the PCM
coder, 6 is a delay circuit, 7 is a PCM decoder, 8
is a transmitter, 9 is a comparison circuit, 10 is a threshold generation circuit,
11 is a first threshold control circuit, 12 is a second threshold control circuit, 13 is a voice detection circuit, 14 is an antenna switch, 15 is an antenna, 16 is a receiver, 17 is a transmission time monitoring timer, and 18 is a level. 19 is a comparison circuit, a timer for monitoring the listening time, and 20 is a timer for monitoring the end of the call.

In FIG. 1, for example, a voice signal from a telephone 1A is transmitted and received between a sending path 3 and a receiving path 4 via an exchange 2. In FIG. The audio signal on the transmission path 3 passes through the PCM coder 5, and the polarity bit is changed to 1 every 125 μs, for example.
The signal is encoded into an 8-bit digital code string, passed through a delay circuit 6 made of memory, given the required delay, passed through a PCM decoder 7, converted back to an analog audio signal, and inputted into the transmitter 8. Ru. At this time, the digital signal from the PCM coder 5 is applied to the comparator circuit 9, and the digital signal from the PCM coder 5 is applied to the threshold generation circuit 1.
Digitally compared to a zero threshold signal. The comparison circuit 9 compares the 7 bits indicating the amplitude of the digital audio signal from the PCM coder 5 excluding the polarity bit with the threshold value output from the threshold value generation circuit 10.
When the audio signal exceeds the threshold value, an audio detection signal is sent to the audio detection circuit 13. When the signal from the comparison circuit 9 continues for a predetermined period of time or more, the voice detection circuit 13 determines that there is voice, generates a transmission start signal, and applies it to the transmitter 8 and the antenna switch 14. As a result, the antenna switch 14 is switched to the transmitter 8 side, and the transmitter 8 is activated to generate a radio frequency signal consisting of a modulated wave signal by the analog audio signal of the PCM decoder 7. This signal is sent to the terminal via the antenna 15. On the other hand, when the voice detection circuit 13 does not determine that there is voice, no transmission start signal is generated, and the antenna switch 14
At the same time, the receiver 16 becomes operational, and the radio frequency signal from the terminal is converted into an audio signal in the receiver 16 and sent to the receiver channel 4.
and is transmitted to telephone 1A via exchange 2.

In the wireless telephone device shown in FIG. 1, in order to combine a single frequency simplex wireless device and a two-wire telephone, a voice detector determines the presence or absence of voice. The transmitter is activated to transmit a message, but due to a delay in detection in the voice detector, a delay in the rise of transmission in the transmitter, a delay in the rise of the squelch circuit in the receiver on the terminal side, etc. There is a considerable time delay before the message is received by the terminal, resulting in the phenomenon of so-called interruptions at the beginning of a conversation. In FIG. 1, a delay circuit 6 is provided to compensate for all such delays and to prevent the beginning of a conversation.

FIG. 2 shows an example of the hangover characteristics of the voice detection circuit 13 in the radio telephone device of FIG. 1, in which the horizontal axis shows time and the vertical axis shows the time to maintain the voice detection state after voice disappears. In other words, it shows the hangover time. In the figure, (A) shows a state where there is no call. (B) shows phase 1 during voice detection, with a hangover time that increases linearly with the duration of the voice detection signal. (C) shows phase 2 during voice detection, which is given a relatively small constant hangover time for a certain period of time. (D) indicates that a call is in progress, and the digital signal from the PCM coder continues to be smaller than the threshold signal of the threshold generation circuit during voice detection 1 and voice detection 2, so the hangover time is zero. Unless this happens, at the end of the voice detection period 2, a sufficiently large hangover time of, for example, several hundred milliseconds is given, and it is determined that the call is in progress, and a transmission activation signal is generated. The reason why a small hangover time is maintained for a certain period of time in phase 2 during a call is to prevent the voice detection circuit from malfunctioning due to short-term noise or the like and determining that the call is in progress.

In the radiotelephone device shown in FIG. 1, the determination of the presence or absence of voice in the voice detection circuit depends on the output of the comparison circuit, as described above. Therefore, by changing the threshold level of the threshold generation circuit, the sensitivity of the voice detector can be controlled. FIG. 3 shows a threshold generation memory in the threshold generation circuit 10. In the same figure, 21, 22, 23 and 24
are the first, second, third and fourth memory respectively.
It shows a block. Each block is 16
It is composed of words, and therefore, for each block, for example, 16 levels of threshold values can be generated in 1 dB steps as a 7-bit code. These 16 types of threshold values are set to gradually increase in order from the lowest address number to the highest address number, and one of the blocks is selected based on the control of the threshold value control circuit 12, and one block is selected based on the control of the threshold value control circuit 11. One threshold value in the selected block is selectively output.

On the other hand, the threshold value control circuit 11 controls the threshold value generation circuit 10 based on the signal from the talking time monitoring timer 17. The transmission time monitoring timer 17 monitors the time during which the voice detection circuit 13 determines that there is voice, and when the time exceeds a predetermined time, it generates a signal and inputs it to the threshold control circuit 11. Threshold control circuit 11
This controls the threshold generation circuit 10,
Increase the threshold by one level. Threshold control circuit 11
By repeating such control based on the output of the speech time monitoring timer 17, the control is performed until the time at which the voice detection circuit 13 determines that there is voice becomes a predetermined time, for example, several seconds or less, and the voice is detected. Decrease the sensitivity of the detector. Furthermore, the threshold control circuit 11
controls the threshold value generation circuit 10 based on the signal of the listening time monitoring timer 19. The listening time monitoring timer 17 receives a signal from the audio detection circuit 13 indicating that it is not determined that there is a voice, and a signal from the receiver 16 indicating that a wireless signal from a terminal is being received, such as a carrier wave detection signal. When the time exceeds a predetermined time, a signal is generated and inputted to the threshold control circuit 11. The threshold control circuit 11 thereby controls the threshold generation circuit 10 to lower the threshold by one level. Threshold control circuit 1
1, by repeating such control based on the output of the listening time monitoring timer 17, the voice detection circuit 13 does not determine that there is voice and the receiver 16
The sensitivity of the voice detector is increased by controlling the voice detector until the time during which the voice detector is receiving the wireless signal from the terminal becomes less than a predetermined time, for example, 20 seconds. In this way, the threshold value control circuit 11 is controlled by both the talking time monitoring timer 17 and the talking time monitoring timer 19, and finally settles into a state in which the threshold value generating circuit 10 generates a certain threshold level. This threshold level is the most appropriate level at which the voice detector will not operate due to background noise, and the voice detector will not determine that there is voice even though the caller is speaking. This type of control is possible because, in normal conversation, the time during which syllables occur consecutively is limited, usually around a few seconds, and therefore, if there is a voice detection signal output that exceeds this time, noise In this case, the sensitivity of the voice detector can be gradually lowered to prevent a voice detection signal from occurring for a predetermined period of time or longer. If it is not determined that there is a signal, and the receiver is in the receiving state for more than the above-mentioned period of time, the sensitivity of the voice detector is too low even though the caller is transmitting on the phone. This is because it can be assumed that this is because the voice is not in a transmitting state, so the sensitivity of the voice detector can be controlled to gradually increase.

In the sensitivity control method of the present invention, the threshold value control circuit 11 is further controlled by the output of the end-of-call time monitoring timer 20. The end time monitoring timer 20 is
When the voice detection circuit 13 does not determine that there is voice and the receiver 16 does not receive a wireless signal from the terminal for a predetermined period of time, for example, 10 seconds, an output is generated and input to the threshold control circuit 11. Threshold control circuit 1
1 thereby controls the threshold generation circuit 10 to select a predetermined value from among the threshold values in the threshold generation memory. The threshold value selected in this way is used as the initial value for the next call, and the detection operation of the voice detector is started from this value.

This kind of control is possible because, as mentioned above, in normal conversation, both parties do not maintain silence for more than several tens of seconds, and therefore the voice detector does not judge that there is a voice after this time. If the receiver does not receive a signal from the terminal, it can be assumed that neither the telephone nor the terminal can transmit and the call has ended. Setting the value to a value prevents voice detection in the next call from being performed using the sensitivity set corresponding to the previous call.

Further, in FIG. 1, the level comparison circuit 18 compares the level of the audio received by the receiver 16 with a reference value, and generates a discrimination output in four stages. The threshold control circuit 12 selects a block in the threshold generation circuit 10 in response to the four-stage discrimination output of the level comparison circuit 18. The second threshold generation memory
Blocks 22 each have a threshold equal to that of the first block 2.
1, the third block 23 has each threshold 6 dB higher than the corresponding threshold in the first block 21, and the fourth block 24 has each threshold 11 dB higher than the corresponding threshold in the first block 21. . Therefore, for the same audio signal level from the PCM coder 5, the magnitude of the threshold value of the threshold value generating circuit 10 changes depending on the received audio level of the receiver 16. This is transmission path 3
and the receiving channel 4 are connected to the telephone set via a hybrid in the exchange 2, which causes detours from the receiving channel to the transmitting channel, and therefore it is necessary to reduce the sensitivity of the voice detector. This is because the higher the level, the greater the wraparound, so the threshold value needs to be set higher accordingly. In this way, the threshold generated by the threshold generation circuit 10 is determined according to both the audio signal level of the sending path and the audio signal level of the receiving path, but the initial value at the end of the call is set as described above. Regardless of these factors, a constant value, for example, the threshold accumulated at the first address "0" of the first block, is always output.

Effects of the Invention As explained above, according to the sensitivity control method of the present invention, in a wireless telephone device that activates a transmitter and transmits a call when a voice is detected by a voice detector, the voice detector monitors the time when the receiver does not determine that there is a voice and the receiver is not in the receiving state, and when that time exceeds a predetermined time, it is assumed that the call has ended and the sensitivity of the voice detector is set in advance. Can be set to the initial value. Therefore, if such control is not carried out, the voice detector will start operating from a sensitivity determined based on the monitoring of the previous call path time and the listening time, and thus the desired control state. This is extremely effective because it can prevent situations from occurring that require a long time to settle down.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a radio telephone device to which the present invention is applied as an embodiment of the sensitivity control method of the present invention, Fig. 2 is a diagram showing hangover characteristics of a voice detection circuit, and Fig. 3 is a diagram showing threshold generation. FIG. 3 is a diagram showing a threshold generation memory in the circuit. 1A,...,1N: telephone, 2: exchange, 3: sending line, 4: receiving line, 5: PCM coder, 6: delay circuit, 7: PCM decoder, 8: transmitter, 9: comparison circuit, 10: Threshold generation circuit, 11, 12: Threshold control circuit, 13: Voice detection circuit, 14: Antenna switch, 15: Antenna, 16: Receiver, 17: Speech time monitoring timer, 18: Level comparison circuit, 19:
Call reception time monitoring timer, 20: Call end time monitoring timer.

Claims (1)

[Claims] 1. When an audio signal is detected in the transmission path, the antenna is connected to the transmitter and the transmitter is activated to set the transmitting state; when no audio signal is detected, the antenna is connected to the receiver and the receiver is set to the receiving state;
control for reducing the sensitivity of the voice detector so that the time during which the voice signal is detected is equal to or less than a first time predetermined corresponding to the time at which syllables occur consecutively in normal conversation; and the voice signal. In a wireless telephone device, the sensitivity of the voice detector is increased so that the time period during which the receiver is not detected and the receiver is in the receiving state is equal to or shorter than a predetermined second time period, which is longer than the first time period. A timer means for counting the time when the voice detector does not detect a voice signal and the receiver is not in a receiving state, and the counting time of the timer means corresponds to the time during which both parties may maintain silence in a normal conversation. and a control means for generating a control signal to set the sensitivity of voice detection in the voice detector to an initial value when the third predetermined time period is exceeded.