JPS6319102B2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention provides a method for controlling the sensitivity of a voice detector in a wireless telephone device that activates a transmitter to transmit a call when a voice is detected by a voice detector. for,
This relates to a sensitivity control method.

Prior Art and Problems Radio telephone equipment that uses a voice detector to detect voice and activates a transmitter using the output to send a call is a two-wire telephone to a single frequency simplex system. This is used in communication systems that make calls via radio equipment.

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 to avoid situations where 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 be too low, resulting in problems such as voice transmission not being activated smoothly.

Purpose of the Invention The present invention aims to solve the problems of the prior art as described above, and its purpose is to provide a method for starting a telephone call by activating a transmitter when a voice is detected by a voice detector. In the wireless telephone device of It is an object of the present invention to provide a system that can prevent a transmitter from being unduly activated due to background noise other than the voice of a caller.

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 time during which the voice detector determines that there is voice, and if the voice detector still outputs a voice determination output after a certain period of time, the caller's It was determined that the voice detector was malfunctioning due to a signal other than voice, and the sensitivity of the voice detector was switched in stages and gradually lowered, so that the sensitivity was automatically adjusted to the appropriate level. It is something.

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, and connects the antenna to the transmitter using the antenna switcher to send out a call signal. It's getting old.

In Fig. 1, 1A, ..., 1N are telephones,
2 is the exchange, 3 is the sending line, 4 is the receiving line, and 5 is the receiving line.
PCM coder, 6 a delay circuit, 7 a PCM decoder, 8 a transmitter, 9 a comparison circuit, 10 a threshold generation circuit, 11 a first threshold control circuit, 12 a second threshold control circuit, 13 audio 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 comparison 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 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 represents time and the vertical axis represents the time to maintain the voice detection state after the voice disappears. Indicates some hangover time. In other words, the hangover time indicates how long a state in which the audio signal remains below the threshold value continues for the audio detection circuit to determine that there is no audio.

In FIG. 1, the transmission activation signal output from the voice detection circuit 13 has a hangover time of 0.
It remains on until the That is, the transmission activation signal activates the transmitter until the audio detection circuit determines that there is no audio.

This hangover time is given in order to prevent the voice detection circuit from determining that there is no voice and turning off the transmission activation signal during the pause time that occurs during a call, and is a period of several 100 msec. is assigned.

In the hangover characteristics of the voice detection circuit shown in FIG. 2, (A) shows a no-call state.
In other words, this area indicates a state in which the audio detection circuit determines that there is no audio since there is no audio level exceeding the threshold.

(B) shows phase 1 during voice detection, and is given a hangover characteristic that increases linearly according to the duration of the voice detection signal. In other words, this region indicates a state where the audio level exceeding the threshold has begun to be detected. In this state, the hangover time increases over time as long as audio levels above the threshold are detected. But time B
The hangover time given at the point in time when the time has elapsed is approximately several tens of milliseconds.

(C) shows phase 2 during voice detection, where a relatively small constant hangover time is given for a certain period of time. That is, in this region, even if an audio level exceeding the threshold is detected, the short hangover time given in (B) is maintained. However, if no audio level above the threshold is detected, the hangover time is reduced. i.e.
Region (C) is a time period in which the voice detection circuit monitors to prevent the transmission activation signal from being turned on accidentally due to pulse noise. Up to this region (C), the voice detection circuit keeps the transmission activation signal in the OFF state.

(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 becomes 0. Unless otherwise, a sufficiently long hangover time, for example, several 100 msec, is given at the end of the voice detection period 2, and it is determined that the call is in progress, and a transmission activation signal is generated.

That is, when the hangover time does not become 0 in the time domain (C) and enters the time domain (D), the voice detection circuit determines that there is voice and turns on the transmission activation signal. In order to avoid turning off the transmission activation signal due to a short pause time during a call,
A long hangover time of sec is given.

The reason why a short hangover period is set for a certain period in the second phase during voice detection is to prevent the voice detection circuit from malfunctioning due to short-term noise and the like and determining that a 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. This is because in normal conversation, the time during which syllables occur consecutively is limited and is usually about the time mentioned above, so the output of a speech detection signal that exceeds this time is due to malfunction of the speech detector due to noise. Therefore, in such a case, the sensitivity of the voice detector is gradually lowered so that the voice detection signal is not output for a predetermined period of time or more. can be placed in optimal operating condition.

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 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 any one block in the threshold generation circuit 10 in response to the four-stage discrimination output of the level comparison circuit 18. The second block 22 in the threshold generation memory has each threshold value 3 dB lower than the corresponding threshold value in the first block 21.
and the third block 23 has a respective threshold value equal to the first
6 dB higher than the corresponding threshold in block 21, and fourth block 24 has its respective threshold 11 dB higher than the corresponding threshold in 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 means that the sending path 3 and the receiving path 4 are connected to the telephone set via a hybrid in the exchange 2.
This causes loop noise from the receiving channel to the sending channel, and it is therefore necessary to lower the sensitivity of the voice detector.The higher the received voice level is, the larger the loop loop is, so the threshold value needs to be increased accordingly. This is because there is.

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 The sensitivity of the voice detector is automatically adjusted according to the environment in which the caller is placed, by controlling the sensitivity of the voice detector to be lowered so that the time it takes for the caller to determine that there is voice is a predetermined time. This is extremely effective because it prevents the transmitter from being activated improperly due to background noise other than the voice of the caller.

[Brief explanation of the drawing]

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,..., 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: Speech time monitoring timer, 18: Level comparison circuit.

Claims (1)

[Claims] 1. In a radio telephone device that activates a transmitter to enter a transmitting state when a voice signal in a transmission path is detected, threshold generation means generates thresholds of successively different levels in accordance with a control signal; an audio detector that compares the level of the signal with a threshold of the threshold value generating means and activates a transmitter to enter a transmitting state when the audio signal exceeds the threshold level; a timer means for counting the time during which the sound detector is detecting; and when the counting time of the timer means exceeds a predetermined time, a control signal is generated to increase the threshold level generated by the threshold value generation means one step at a time. A sensitivity control method characterized by comprising a threshold value control means.