JPH04192990A - Signal discriminating circuit - Google Patents

Abstract

PURPOSE:To improve the reliability of signal discrimination by providing an FFT processing means to calculate the frequency spectrum data from a signal and a means to discriminate the prescribed signal from the frequency spectrum data. CONSTITUTION:When the above circuit is used as the line wire transmitting tone detecting circuit of a domestic simplified telephone exchange and a ring back tone is discriminated, a spectrum deciding circuit 23 detects a maximum value L in the range of 380-420Hz from the frequency spectrum data calculated by an FFT processing circuit 22 and when a frequency obtaining the maximum value L is defined as (f), a maximum value La is detected in the range of f-20 to f-15Hz. Next, a maximum value Lb is detected in the range of f+15 to f+20Hz and judgement is executed. Thus, since the signal is judged from the frequency spectrum data, the feature of the signal can be extremely precisely judged and therefore, the reliability of signal discrimination is improved so as to discriminate the signal with high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal discrimination circuit that discriminates signals from frequency spectra.

[Conventional technology]

Conventional signal discrimination circuits are constructed using filters, and signal discrimination is performed based on whether a signal of a predetermined frequency is present. This type of signal discrimination circuit is used, for example, in telephone equipment, etc., and is used to determine whether or not it is possible to make an outside line call, or whether or not the transmission of the dial signal sent when making an outside line call has finished. It was getting worse.

[Problem to be solved by the invention]

Incidentally, the signals used in devices such as the above-mentioned telephone equipment have a certain degree of variation in their frequencies, and therefore, a filter having a passband corresponding to the width of the variation must be used. Therefore, a signal other than a predetermined signal such as a voice may be mistakenly determined as a predetermined signal, resulting in a problem that the reliability of signal discrimination is low.

The present invention has been made in view of the above points, and an object thereof is to provide a signal discrimination circuit that can perform highly reliable signal discrimination. - [Means for Solving the Problem] In order to achieve the above object, the present invention provides FFT processing means for obtaining frequency spectrum data of a signal, and discrimination means for discriminating a predetermined signal from the frequency spectrum data. We are prepared.

[Effect]

By having the above-described configuration, the present invention enables highly accurate signal discrimination by discriminating signals from frequency spectra.

〔Example〕

An embodiment of the present invention is shown in FIGS. 1 to 5.

In this embodiment, the present invention is applied to a simple telephone exchange for home use, and the simple telephone exchange for home use will be explained first.

As shown in FIG. 5, the household simple telephone exchange device connects an outside line, which is a public telephone line, via a disconnector G and a protector H. !
A telephone exchange A is connected to a telephone office E at , and a commercially available telephone C is removably connected to this telephone exchange A through an extension l as a telephone line and a control line l as a signal transmission line. It consists of a plurality of telephone outlets B, and the telephone exchange A has an outside line 11 and an extension L, or an extension 12.
By switching the communication paths between the two, it is possible to make outside calls and internal calls using the telephone set C connected to the telephone outlet B. In addition, in this home simple telephone exchange device, the door phone D can be connected to the telephone exchange A using the call JIJ4, and the door phone call can also be made using the telephone C.

Each telephone outlet B is provided with a modular jack M, through which a general commercially available telephone C can be detachably connected. In addition, this telephone outlet B is connected to a speaker SP for reproducing notification signals such as an extension ring tone or a door phone ring signal sent via the control line l, and a speaker SP which is sent via the control line l. a light-emitting display section La that distinguishes a display signal that is a voltage signal to indicate whether an internal call is in progress or an external call is in progress;
Lb, and these speakers SP and light emitting indicators La and Lb are used to perform notification and display operations.

Note that the volume of the speaker SP can be adjusted using a volume control switch vS.

The configuration of the telephone exchange will be briefly explained along with its operation. At telephone exchange A, as shown in Figure 4, telephone outlet B
Relay contacts r1 to r are provided for each extension 12 to which extension I! 2 and outside line! ! , and extension 12 is now an outside line! ! The communication current for extension calls or doorphone calls in a state of being disconnected from the communication current supply circuit 4.1 is supplied to the communication current supply circuit 4. ~4. It should be supplied from In addition, the above relay contacts r1~
r is normally switched to the side that disconnects the extension l from the outside line 11, and is switched to the outside line 11 side when an outside line call is received.

Now, suppose that an incoming external call is detected by the incoming call detection circuit 5.
A control circuit 11 composed of a CPU connects relay contacts r, to r
, to the outside line IT side, sends an outside line incoming signal sent through the outside line 11 to telephone C, and rings a built-in ringer or the like in telephone C to make an outside line call. When the user picks up the handset of telephone C in response to this call, an outside call becomes possible. By the way, hook/DP detection circuits 21-2. It is designed to detect the dial signal from the dial pulse (DP) signal input from telephone C and the hook state of telephone C, and as mentioned above, when telephone C goes off-hook when receiving an outside call. is the hook/DP detection circuit 2 corresponding to the telephone C.
Upon receiving the output of By lighting up La, it is displayed that an outside line call is in progress. An amplifier AMP is inserted into the transmission path of the display signal and the notification sound signal to be described later to amplify the signals.When making an outside line call from the telephone set C, the receiver is lifted up and dialed. In the following explanation, the case where the telephone line contract is a dial pulse line will be explained. The off-hook state of the telephone C is detected by the hook/DP detection circuit 2, and at this time the control circuit! (2) drives the signal tone generation circuit 20 to generate a pseudo dial tone similar to the dial tone (two tone) sent from the telephone office to the extension I.
! 2 to telephone C. Note that the sending of this pseudo dial tone is stopped when the hook/DP detection circuit 2 detects the first dial signal. By the way, in this type of home simple telephone switching device, calls such as internal calls are processed by inputting a specific dialing signal from telephone C, so even if a dialing operation is performed on telephone C, an outside call is not processed. It does not necessarily have to be an outgoing call, but may be a call processing such as an extension call. Therefore, the control circuit 11 that receives the dial signal starts making an outside call only when the number of digits of the dial signal exceeds the number of digits of the dial signal (two digits in the case of this embodiment) assigned for call processing. Start. This external line transmission is performed by driving the DP sending circuit 6 and connecting the diode bridge DB.
This is done by sending a DP double signal to the outside line 11 via. When the other party answers in response to this outside line call, the polarity of the outside line L is reversed, and this polarity reversal is detected by the polarity reversal detection circuit 16, after which the outside line 11 and the telephone C that made the outside line call are connected. Relay contact r is switched to connect the extension line 12 to enable an outside line call. At this time as well, the display control circuit 18 causes the telephone outlet B to display an outside line call in progress. Moreover, after the polarity reversal is detected by the polarity reversal detection circuit 16, the outside line! Both ends of the diode inserted in , are short-circuited by relay contact r4 to eliminate an increase in the direct current resistance of the telephone connected to outside line l. Further, a dial tone, such as a busy tone, sent through the outside line 1+ is detected by the outside line dial tone detection circuit 8, and at that time, the signal tone generating circuit 20 sends the telephone C that made the outside line call to the extension l. A busy tone is sent through the terminal.

When making an extension call, a dial signal is input using the telephone C in the same manner as when making an outside call. The control circuit 11 determines that this is an extension call from the number of digits in the dial signal, and at this time drives the notification sound generation circuit 17 to call the telephone through the control line l corresponding to the telephone C on the called side. A notification tone signal is sent to outlet B, and an extension ring tone is sounded from speaker SP of telephone outlet B. Then, the hook/DP detection circuit 2 detects that the telephone C on the called side responds and is off-hook, and the control circuit 11 controls the crosspoint switch 10 to control the telephone C on the calling side.
The extension 12 corresponding to the telephone C on the called side is connected to the extension 12 corresponding to the telephone C on the called side, thereby enabling an extension call. At this time, the display control circuit 18 causes the telephone outlet B to display the extension call status.

Incidentally, although the above-mentioned extension call is made to a specific telephone C, if the telephone C to be called is unspecified, it is possible to make a general call. In this case, when a dial signal corresponding to simultaneous ringing is input from telephone C, an extension ring will sound from each telephone outlet B at the same time, and if any telephone C goes off-hook in response to this ringing, Upon receiving the detection output of the hook/DP detection circuit 2 corresponding to the telephone C, the control circuit 11 connects the extension l corresponding to the telephone C and the extension l corresponding to the calling party's telephone C, and performs an extension call. is possible.

Furthermore, this home simple telephone exchange device is equipped with a hold tone sending circuit 9 that allows a hold operation to be performed and sends out a hold melody tone. In addition, if the telephone line contract is a button line, the PB receiver 12.13 detects a dial signal based on the PB double signal from the button type telephone C, and the DC connection circuit 3 closes the line. The operation is the same as in the case of the dial pulse line, except that the PB dialer 7 sends a dial signal to the outside line 11 in the state in which PB dialer 7 is in use.

Furthermore, a power supply voltage detection circuit 19 for detecting a drop in the power supply voltage is provided to cope with the case where the contents stored in the buffer inside the control circuit 11 are destroyed due to a drop in the power supply voltage.

The signal discrimination circuit, which is a feature of this embodiment, will be explained below. Incidentally, this signal discrimination circuit is used as the outside line dial tone detection circuit 8 in the case of the above-mentioned household simple telephone exchange device. This signal discrimination circuit, as shown in Figure 1,
An A/D conversion circuit 21 that converts an outside line dial tone into a digital signal, and a digital signal processor (DSP)
It is comprised of an FFT processing circuit 22 that obtains frequency spectrum data of the digitally converted signal using the above-described method, and a spectrum discrimination circuit 23 that discriminates a predetermined signal from the frequency spectrum data.

This signal discrimination circuit detects the ring back tone (RB
The case of determining T) will be explained.

The ring back tone is a signal of 400±20Hz modulated with a signal of 15H2 to 20Hz, and as shown in Figure 2, the maximum spectrum appears at 400±20Hz. A spectrum smaller than the maximum spectrum appears above and below it from 15 Hz to 20 Hz. Therefore, the spectrum determination circuit 23 performs the following determination based on the frequency spectrum data shown in FIG. 2 obtained by the FFT processing circuit 22 to determine the ring back tone. First, 3
The maximum value in the range of 80 Hz or more and 420 Hz or less is detected. Then, the frequency at which the maximum value was obtained is f
If , (f-20) Hz or higher (f-15) Hz
The maximum value La in the range of is detected, and its size is L
Check that the value is greater than or equal to wa I s and less than or equal to 1.1. Here, L.

, L31, is the value obtained from the modulation rate, and
In the case of back tone, the modulation rate is within 85±15%, so L, 6 is 0.35XL, L□8 is 0.5XL
It will be about. Next, it is confirmed that among the spectral components between the frequencies fa and f from which La was obtained, there is one whose magnitude is smaller than La. Furthermore, (f+15)Hz
With the above, detect the maximum value Lb in the range of (f + 20) H2, confirm that its magnitude is greater than or equal to L wa + a and less than L□0, and find that the frequency from which Lb was obtained is between fb and f Confirm that some of the spectral components have a magnitude smaller than Lb. When such a determination is made and all of these conditions are satisfied, it is determined that the tone is a ring back tone. A flowchart summarizing the above determination operation is shown in FIG.

Distinguishing signals from their frequency spectra in this way makes it possible to determine extremely detailed signal characteristics as described above, which increases the accuracy of signal discrimination and enables highly reliable signal discrimination. . In this embodiment, a case where a ring back tone is discriminated is exemplified, but it goes without saying that other signals can also be discriminated in a similar manner.

〔Effect of the invention〕

As described above, the present invention includes an FFT processing means for obtaining frequency spectrum data of a signal and a discrimination means for discriminating a predetermined signal from the frequency spectrum data. By performing the discrimination, highly accurate signal discrimination becomes possible, and the multiplicity of the signal discrimination can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a specific configuration of a signal discrimination circuit according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the frequency spectrum of a ring back tone, and FIG. 3 is a flowchart showing the discrimination operation of the same. , FIG. 4 is a circuit diagram of a telephone exchange of a household simple telephone exchange device to which the above is applied, and FIG. 5 is a system configuration diagram of the same. 21 is an A/D conversion circuit, 22 is an FFT processing circuit, and 23 is a spectrum determination circuit. Agent Patent Attorney Stone 1) Long 7 ib I ia 2g 3EIO≦420 f-20aafalf-15 f+15≦fbit◆20

Claims (1)

[Claims] (1) FFT to obtain frequency spectrum data of a signal
1. A signal discrimination circuit comprising processing means and discrimination means for discriminating a predetermined signal from frequency spectrum data.