JPS642297B2 - - 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 controlling the sensitivity of a voice detector.

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, a voice detector used for the purpose of switching between transmission and reception using voice has a 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. In some cases, the level was too low, causing problems such as voice transmission not being able to be activated smoothly.

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 of To provide a system capable of preventing a transmitter from not being activated because a voice detector does not determine that there is voice when the voice level of a caller is low.

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 only a few seconds at most, and never for several tens of seconds. Focusing on this, we monitor the amount of time that the audio detector determines that there is no audio and the receiver continues to receive radio waves, and if this state continues even after a certain period of time has elapsed, It determines that the voice detector is not working properly because the sensitivity of the voice detector is too low, and automatically adjusts the sensitivity to the appropriate level by increasing the sensitivity of the voice detector in stages. It was designed so that

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 listening time monitoring timer, and 18 is a level comparison It is a circuit.

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 and a call is made, but at this time, due to a detection delay in the voice detector, a delay in the rise of transmission in the transmitter, and a delay in the rise of AGC in the receiver on the terminal side, etc.
There is a considerable time delay between the generation of the voice and the reception at the terminal, resulting in a so-called phenomenon where the beginning of a conversation is cut off. 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 5 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. Detecting audio 2 unless .
At the end of the time, a sufficiently long 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 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 of the listening time monitoring timer 17. 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. By repeating such control based on the output of the listening time monitoring timer 17, the threshold control circuit 11 prevents the voice detection circuit 13 from determining that there is voice and the receiver 16 receiving the wireless signal from the terminal. The sensitivity of the voice detector is increased by controlling the voice detector until the time for which the sound has been on is equal to or less than a predetermined time, for example, 20 seconds. This is because, in normal conversation, the time during which syllables occur consecutively is limited and usually lasts only a few seconds, so the above-mentioned time period during which it is not determined that there is voice on the sending channel and the receiver is in the receiving state is limited. If this continues for longer than , the phone determines that the voice detector is too sensitive to enter the transmitting state even though the caller is transmitting, and the voice detector By gradually increasing the sensitivity of the audio detector, the audio detector can be placed in an optimal operating state.

In this case, the initial value of the threshold value in the threshold value generating circuit 10 may be set to a constant value at the end of a call, for example, so that control starts from a constant value for each call.

Further, in FIG. 1, the level comparison circuit 18 is
The level of the audio received by the receiver 16 is compared with a reference value, and a discrimination output is generated 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 channel and the audio signal level of the receiving channel.

Effects of the Invention As explained above, according to the sensitivity control method of the present invention, in a wireless telephone device of a type in which a transmitter is activated to transmit a call when a voice is detected by a voice detector, the voice detector By controlling the sensitivity of the voice detector to increase so that the receiver does not judge that there is voice and the receiver is in the receiving state and keeps the time below a predetermined time. The sensitivity of the voice detector is automatically set according to the environment in which the caller is placed, and the transmitter is activated even though the caller is talking because the sensitivity of the voice detector is too low. This is extremely effective because it prevents the device from being activated and therefore from not being in the transmitting state.

[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 example 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,..., 1B: 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: Listen time monitoring timer, 18: Level comparison circuit.

Claims (1)

[Claims] 1. A wireless telephone that connects the antenna to the transmitter and activates the transmitter to enter the transmitting state when a voice signal is detected on the transmission path, and connects the antenna to the receiver and enters the receiving state when no voice signal is detected. In the device, a threshold generating means sequentially generates thresholds of different levels according to a control signal, and a level of the audio signal in the transmission path is compared with the threshold of the threshold generating means, and the audio signal exceeds the threshold level. a voice detector that activates the transmitter and puts it into a transmitting state; a timer means that counts the time during which the voice detector detects no voice signal and the receiver is in a receiving state; and a counting time of the timer means. threshold control that sequentially lowers the threshold level generated by the threshold generating means by one step by generating a control signal when the time exceeds a predetermined time corresponding to the time during which syllables occur continuously in normal conversation. A sensitivity control method characterized by comprising means.