JP3336556B2 - Telephone busy tone detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a busy tone detection circuit of a telephone.

[0002]

2. Description of the Related Art Conventionally, in a telephone having a hands-free function, a busy tone (BUSY TONE (BT): 0.5 at a frequency of 400 Hz) generated when a user on-hook the telephone during a hands-free call. There is an intermittent tone with a second transmission and a 0.5-second pause, for example, which is configured so that the user's telephone set enters a call end operation upon detecting a for example a waveform shown in FIG. That is, a voice signal during a call is detected by a VOX (Voice Operated Transmittion) detection circuit connected to the speech network, and a pattern of a period t of voiced or silence of the pulsed voice signal from the VOX detection circuit is determined. A microcomputer (hereinafter referred to as a microcomputer) reads the pattern, and the pattern matches the pulsed busy tone pattern (FIG. 4B) stored in the ROM memory in advance.
If the pattern matches have continued N times, the microcomputer determines that the sound is a busy tone, and starts a call ending operation. At this time, the microcomputer changes the output level of the VOX detection circuit (H → L or L).
“H” and “L” are determined at the time of (H). (Note that the microcomputer reads "H" and "L" at a constant cycle even after the determination.)

The above operation will be described with reference to the flowchart of FIG. 6. First, in step S21, the microcomputer reads the output from the VOX detection circuit and determines the level of H or L. Next, the microcomputer checks whether or not the final value is different from the previous reading (S22).
Proceed to 23, and if no, return to S21. Step S23
Then, it is checked whether or not the cycle confirmation timer has been started. If the determination is yes, the process proceeds to S24. If the determination is no, the cycle confirmation timer is started (S25), and the process returns to S21. In step S24, the value "t" of the period confirmation timer is checked. Then
Check whether “t” is within the busy tone standard (S
26) If yes, proceed to S27; if no, S21
Return to Next, in step S27, the busy tone counter is incremented (+1), and it is checked whether the count value of the busy tone counter has reached N (for example, N = 3) (S28). If no, S
Returning to step 21, the above operation is repeated. And step S
If it is determined in step 29 that a busy tone has been detected, a call termination process is performed based on this determination (S30).

[0004]

However, when the microphone is used in a hands-free state, the microphone picks up an external sound, and the sound is input to the VOX detection circuit together with the busy sound as a side tone (FIG. 5 ( A) Side tone). In addition, even during a normal call other than the hands-free call, noise from the line may enter. The microcomputer cannot distinguish between busy sound and noise from the microphone, so "H", "L"
Until the pattern of the period (FIG. 5 (B)) matches the pattern of the busy tone, the line ending operation is not started, so that the line may remain connected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a busy tone detecting circuit of a telephone which can solve the problems at the time of detecting a busy tone in the related art and prevent erroneous detection due to noise.

[0006]

A busy tone detecting circuit for a telephone according to the present invention comprises a detecting means for detecting the presence or absence of a voice, and a busy tone detecting means for detecting a voice pattern detected by the detecting means. compared with the pattern, when both patterns coincide, the busy tone detecting circuit of the telephone which includes a determination means that the busy signal, determine a constant means prestores pulse Kahanashi tone signal first storage means for a second storage means for storing a pulsed sound signal from the detecting means, the second
The level of the pulsed audio signal read from the storage means
Short confirmation period in smell than the period of the pulse Kahanashi tone signal
Te, a confirmation means for confirming at least n times whether high or low, determination means confirmation result by said confirmation means to determine the high or low levels of pulse speech signal if at least n consecutive times high or low If the first stored probability the determined high and low at a constant means consecutively at least N times
It is intended to include determining means for determining the pulse of the speech signal and the busy tone signal if they match the pulse Kahanashi tone signals stored in the unit.

Further, the detecting means includes a filter which allows only a frequency signal corresponding to a busy tone to pass.

[0008]

In a telephone having a hands-free function, V
The pulsed voice signal from the OX detection circuit is stored in the RAM memory, and it is determined whether the pattern of the pulsed voice signal read from the RAM memory matches the pattern of the pulsed busy tone signal stored in the ROM memory in advance. Confirm.
This confirmation work is pulsed performed at least n times Kahanashi period shorter confirmation periodic of inside sound signal, the level high or low the If level of pulsed audio signal is at least n consecutive times high or low determined as the first memory hand level the determined high or low is continuously N times
If it matches the pulsed busy tone signal stored in the stage ,
It is determined that the pulsed voice signal is a busy tone, and the operation ends. Therefore, even in the hands-free state, a sudden side tone (noise) which is input from the microphone to the VOX detection circuit and which is mixed during the silent period of the busy sound, in particular,
Erroneous detection of the busy tone is eliminated, and as a result, the busy tone is detected with higher accuracy than before, and the telephone can surely start the call ending operation. In addition, a band-pass filter that passes the frequency of the busy sound (400 Hz) is inserted between the speech network and the VOX detection circuit 8 to reduce the occurrence of erroneous detection of the busy sound with respect to continuous noise.

[0009]

FIG. 1 is a block diagram of one embodiment of a busy tone detection circuit of a telephone according to the present invention. FIG. 1 shows the configuration of a main part of a telephone having a hands-free function for explaining the present invention, wherein 1 is a polarity matching circuit, 2 is a hook circuit, 3 is a speech network,
Is a speakerphone circuit, 5 is a loudspeaker amplifier, 6 is a loudspeaker, 7 is a microphone, 8 is a VOX detection circuit, 9 is a microcomputer,
Reference numeral 16 denotes a 400 Hz bandpass filter. In FIG. 1, a voice signal input from a telephone line during a telephone call in a hands-free state passes through a polarity matching circuit 1 and a hook circuit 2, and
After being input to the speech network 3 and subjected to 2-4 line conversion, it is input to the speakerphone circuit 4 and the VOX detection circuit 8. The signal input to the speakerphone circuit 4 is output from the loudspeaker amplifier 5 to the loudspeaker 6. On the other hand, the signal input to the VOX detection circuit 8 is input to the microcomputer 9 as a pulsed audio signal obtained by converting the presence or absence of audio into a pulse at a predetermined threshold level.

The microcomputer 9 includes an input port 10, a CPU 1
1, clock generation circuit 12, ROM memory 13 , RAM
The memory 14 comprises an output port 15 and an input port 10
Is read from the VOX detection circuit 8 and stored in the RAM memory 14 and the pattern is stored in the ROM memory 13.
When the pattern matches the pulsed busy tone pattern stored in advance in the memory 9 and the pattern matches N consecutive times, the microcomputer 9 determines that the tone is a busy tone. Based on the result of this determination, the microcomputer 9 outputs a disconnection signal from the output port 15, turns off the switching transistor Q2 of the hook circuit 2 to go off-hook, and completes the call termination operation.

On the other hand, during a hands-free call, the voice input from the microphone 7 is output to the line in the order of the speakerphone circuit 4, the speech network 3, the hook circuit 2, and the polarity matching circuit 1. There is a sound that returns to the speakerphone 4 as a side tone when the 2-to-4 wire conversion is performed in the network 3, and this is mixed with a busy sound and input to the VOX detection circuit 8. Therefore, in order to reduce the occurrence of erroneous detection of the busy sound with respect to continuous noise, a band-pass filter that passes the frequency of the busy sound (400 Hz) is provided between the speech network 3 and the VOX detection circuit 8. 16 is inserted.

The above operation will be described with reference to the flowchart of FIG. First, in step S1, the microcomputer 9 reads a pulsed sound output (an example of a waveform is shown in FIG. 3) from the VOX detection circuit 8 and stores it in the RAM memory 14 (S2).
Next, the microcomputer 9 checks whether or not the level of the pulsed sound output stored in the RAM memory 14 is continuously "H" n times (for example, n = 4) (S3). Is determined (S4), and if no, the process proceeds to S5.
In step S5, the microcomputer 9 determines that the level of the pulsed sound output stored in the RAM memory 14 is n times (for example, n = 4).
It is confirmed whether or not it is continuously "L". If yes, "L" is determined (S6), and if no, the process returns to S1.
Next, in step S7, it is checked whether the determined value of H or L determined in S4 and S6 is different from the value confirmed last time. If yes, proceed to S8, and if no, return to S1. Next, it is checked whether or not the cycle check timer has started (S8). If the answer is yes, the process proceeds to S9. If the answer is no, the cycle check timer is started (S10), and the process returns to S1. In step S9, the value "t" of the period confirmation timer is checked. Next, it is confirmed whether or not "t" is within the busy tone standard (S11). If yes, the process proceeds to S12, and if no, the process returns to S1. Next, in step S12, the busy tone counter is incremented (+1), and it is checked whether the count value of the busy tone counter has reached N (for example, N = 3) (S13). If not, the process returns to S1 to repeat the above operation. In other words, when the combination of H and L of the determined level occurs, for example, three times consecutively, it is determined that the busy sound has been detected in step S14, and based on this determination, the microcomputer 9 performs the call termination processing. (S15).

[0013]

As described above, according to the busy tone detecting circuit of the telephone according to the present invention, even when the telephone is in the hands-free state, it is input from the microphone, and particularly, suddenly entering the silent part of the busy tone. As a result, erroneous detection is eliminated for a typical noise, and as a result, busy sound detection is performed with higher accuracy than in the past, and it is possible to reliably start a call termination operation.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of a busy tone detection circuit of a telephone according to the present invention.

FIG. 2 is a flowchart illustrating an operation of the busy sound detection circuit of FIG. 1;

FIG. 3 is an output waveform diagram of a VOX detection circuit in FIG. 1;

FIG. 4A is a waveform diagram of a busy tone, and FIG. 4B is a waveform diagram of a pulsed busy tone.

FIG. 5A is an input waveform diagram of a VOX detection circuit in a busy tone detection circuit of a conventional telephone, and FIG. 5B is an output waveform diagram of the VOX detection circuit.

FIG. 6 is a flowchart illustrating the operation of a busy tone detection circuit of a conventional telephone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarity matching circuit 2 Hook circuit 3 Speech network 4 Speaker horn circuit 5 Loudspeaker amplifier 6 Loudspeaker 7 Microphone 8 VOX detection circuit 9 Microcomputer 16 400Hz bandpass filter

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04M 1/00 H04M 1/60

Claims (2)

(57) [Claims] 1. A detecting means for detecting the presence or absence of a voice, and comparing a voice pattern detected by the detecting means with a preset busy voice pattern. A busy tone detection circuit for a telephone, comprising: a first storage unit that stores a pulsed busy tone signal in advance; and a pulsed voice signal from the detection unit. A storage means for storing the level of the pulsed voice signal read out from the second storage means , in a confirmation cycle shorter than the cycle of the pulsed busy sound signal, at least n times as high or low. Confirming means for confirming; confirming means for confirming the level of the pulsed audio signal as high or low if the result of confirmation by the confirming means is high or low at least n times in succession; At least N has been high and low is
Successively stored in the first storage means.
A busy tone detection circuit for a telephone, comprising: determination means for determining the pulsed voice signal as a busy tone signal when the pulsed speech signal matches the busy tone signal . 2. The busy tone detecting circuit for a telephone according to claim 1, wherein said detecting means includes a filter for passing only a frequency signal corresponding to the busy tone.